The Kynix Blog

IntroductionA three-phase circuit consists of a three-phase source, a three-phase load, and a three-phase transmission line. The most basic characteristic of this circuit is that it has one or more groups of power supplies. Each group consists of three sinusoidal power supplies with the same amplitude, the same frequency, 120° phase difference, and the power supply and the load are connected in a specific way. Three-phase circuits are widely used in power systems such as power generation, transmission, distribution, and high-power electrical equipment.What does 3 phase mean?CatalogIntroductionⅠ Three-phase Circuit Basics1.1 Three-phase Circuit Characterized1.2 Three-phase Circuit Terms1.3 Three-phase Voltage & Current1.4 Three-phase Circuit AdvantagesⅡ Symmetrical vs Asymmetrical2.1 Symmetrical Three-phase Circuit2.2 Three-phase AsymmetryⅢ Power in Three Phase Circuit FormulasⅣ Frequently Asked Questions about Three-phase CircuitⅠ Three-phase Circuit BasicsThe three phases could be supplied over six wires, with two wires reserved for the exclusive use of each phase. However, they are generally supplied over only three wires, and the phase or line voltages are the voltages between the three possible pairs of wires. The phase or line currents are the currents in each wire. Voltages and currents are usually expressed as rms or effective values, as in single-phase analysis.1.1 Three-phase Circuit CharacterizedSpecial power supplySpecial loadSpecial connectionSpecial solution1.2 Three-phase Circuit Terms1) End wire (fire wire)2) Neutral line3) Line current4) Line voltage5) Phase current6) Phase voltage7) Three-phase three-wire system and three-phase four-wire system1.3 Three-phase Voltage & CurrentStar ConnectionSummery: Line Voltage vs Phase Voltage1) The line current is equal to the corresponding phase current.2) If the phase voltage is symmetrical, the line voltage is also symmetrical.3) The line voltage is equal to √3 times the phase voltage.4) The phase of the line voltage leads the corresponding phase voltage by 30°. Delta ConnectionSummery: Line Current vs Phase Current1) The line voltage is equal to the corresponding phase voltage.2) If the phase currents are symmetrical, the line currents are also symmetrical.3) The line current is equal to √3 times the phase voltage.4) The phase of the line current lags behind the corresponding phase voltage by 30°.1.4 Three-phase Circuit AdvantagesPower generation: Three-phase power is increased by 50% compared to single-phase power.Transmission: 25% less material than single-phase circuit transmission. That is, under certain conditions, transmitting a certain amount of power by three-phase only requires 75% of the copper of single-phase transmission.Power distribution: More economical than single-phase transformers and easier to connect to the load.Transportation: simple structure, low cost, reliable operation, convenient maintenance.In addition, three wires are usually seen in high-voltage transmission lines, whether on towers or poles, with pin or suspension insulators. Some high-voltage lines are now DC, since solid state devices make it easier to convert to and from AC. The DC lines are free of the problems created by phase, as well as eliminating the skin effect that reduces the effective area of the conductors. It is not nearly as easy to manage long-distance electrical transmission as might be thought.Ⅱ Symmetrical vs Asymmetrical2.1 Symmetrical Three-phase CircuitA symmetrical three-phase power source is usually generated by a three-phase synchronous generator, as shown in Figure (a). Among them, the three-phase windings differ by 120° in space. When the rotor rotates at a uniform angular velocity ω, an induced voltage is generated in the three-phase winding, thereby forming a symmetrical three-phase power supply as shown in Figure (b). Among them, the three ends of A, B, and C are called the start end, and the three ends of X, Y, and Z are called the end. When you connect a load to the three wires, it should be done in such a way that it does not destroy the symmetry.Instantaneous Voltage Calculation of Three-phase PowerIn the formula, take the phase A voltage uA as the reference sine quantity. The three-phase voltage waveform diagram is shown in Figure (a).The key to understanding three-phase is to understand the phasor diagram for the voltages or currents. The phasor of the three-phase power supply can be represented by the Figure (b).The characteristics of the symmetrical three-phase power supply can be derived from the above formula:From the above formula, the sum of the instantaneous value of the three-phase power supply and the sum of the phasor are always zero.The sequence in which each phase of the three-phase power passes through the same value (such as the maximum value) is called the phase sequence of the three-phase power, and the phase sequence of the above-mentioned three-phase voltage is called the positive sequence. Conversely, if phase B exceeds 120° of phase A and phase C exceeds 120° of phase B, this phase sequence is called reverse sequence. If there is no special instructions, it will generally default to positive order.2.2 Three-phase Asymmetry1) In a three-phase circuit, as long as there is asymmetrical part, it is called a three-phase asymmetry.2) The complex power absorbed by the three-phase load is equal to the sum of various complex powers.3) The instantaneous power of a three-phase circuit is the sum of the instantaneous power of each phase load.4) In a three-phase three-wire circuit, whether symmetrical or not, two power meters can be used to measure three-phase power.When the power supply voltage in the three-phase circuit is asymmetrical or the parameters in the circuit are asymmetrical, the current in the circuit is generally asymmetrical. This kind of circuit is called three-phase asymmetry. There are a lot of asymmetry parts in three-phase circuits, and the causes are different. For example, there are many low-power single-phase loads in a three-phase circuit, it is difficult to make them into a completely symmetrical circuit. When a three-phase circuit is broken or short-circuited, it is also a three-phase asymmetry circuit. In addition, some electrical equipment and instruments formally use three-phase asymmetry to work.For example, the most common low-voltage three-phase four-wire system. Due to the large number of single-phase loads in the low-voltage system, the equivalent impedances ZA, ZB, and ZC of the three phases circuit are generally different from each other, and the power supply voltage can generally be considered symmetrical. In this way, a symmetrical three-phase power supply converts to an asymmetrical three-phase load.The circuit shown in the figure has two nodes, and the voltage between the two nodes can be directly calculated according to the node voltage method.Although the power supply voltage in the above formula is symmetrical, the voltage between the neutral point of the power supply and the neutral point of load is not zero due to the load asymmetry, that is, UNN≠0. According to Kirchhoff's voltage law, the phase voltage of the load can be obtained as:The phasor diagram of each voltage corresponding to the above formula is as follows:Ⅲ Power in Three Phase Circuit Formulas1. Average PowerSuppose the power absorbed by a phase load in a symmetrical three-phase circuit is equal to Pp=UpIpcosφ, where Up is the phase voltage and Ip is the phase current of the load. Then the total three-phase power is: P=3UpIpcosφPay Attention To1) φ in the above formula is the phase difference angle (impedance angle) of phase voltage and phase current.2) cosφ is the power factor of each phase, in a symmetrical three-phase system:cosφA=cosφB=cosφC=cosφ3) The formula calculates the circuit power (or the power absorbed by the load).When the load is in a star connection, the line voltage  and line current  at the load end are substituted into the above formula:When the load is in a delta connection, the line voltage  and line current  at the load end are substituted into the above formula:2. Reactive powerThe reactive power absorbed by the load in a symmetrical three-phase circuit is equal to the sum of the reactive power of each phase:3. Apparent Power4. Instantaneous PowerSuppose the voltage and current of phase A of the three-phase load are:Then the instantaneous power of each phase is:It can be proved that their sum isThe above formula shows that the instantaneous power of a symmetrical three-phase circuit is a constant, and is equal to the average power. This is one of the advantages of a symmetrical circuit. For example, on a three-phase motor, a balanced electromagnetic torque is obtained and mechanical vibration is avoided, which is not available in single-phase motors. Ⅳ Frequently Asked Questions about Three-phase Circuit1. What is a 3 phase circuit?Three-phase power is a three-wire ac power circuit with each phase ac signal 120 electrical degrees apart. ... three-phase is that a three-phase power supply better accommodates higher loads. Single-phase power supplies are most commonly used when typical loads are lighting or heating, rather than large electric motors. 2. How many wires are in a 3 phase?four wiresThe three-phase system has four wires. Three are conductors and one is neutral. 3. What is the 3 phase power formula?3-Phase Calculations. For 3-phase systems, we use the following equation: kW = (V × I × PF × 1.732) ÷ 1,000. 4. What is the advantage of three-phase system?A three-phase circuit provides greater power density than a one-phase circuit at the same amperage, keeping wiring size and costs lower. In addition, three-phase power makes it easier to balance loads, minimizing harmonic currents and the need for large neutral wires. 5. What is meant by 3 phase balanced load?A balanced three-phase voltage or current is one in which the size of each phase is the same, and the phase angles of the three phases differ from each other by 120 degrees. ... With such a balanced load, if a balanced three-phase supply is applied, the currents will also be balanced.

IntroductionA stable power supply is necessary for normal operation of the electrical system. Except for the use of solar cells or chemical batteries in certain special occasions, the direct current of most circuits is converted from the alternating current of the grid. The bridge rectifier is commonly used to convert AC into DC, which is the most commonly used circuit that uses the unidirectional conductivity of diodes for rectification. There are many types of bridge rectifiers: flat, round, square, bench-shaped (plug in and SMD), etc., having GPP and O/J structures. The maximum rectified current ranges from 0.5A to 100A, and the maximum reverse peak voltage ranges from 50V to 1600V.What is Bridge Rectifier?CatalogIntroductionⅠ Bridge Rectifier Diode CircuitⅡ Bridge Rectifier Circuit FeaturesⅢ Single Phase Rectification vs Three Phase Rectification3.1 Single Phase Bridge Rectifier Circuit3.2 Three Phase Bridge Rectifier CircuitⅣ Role of Bridge RectificationⅤ Bridge Rectifier Wiring DiagramⅥ Difference between Bridge Rectifier and Full-wave Rectifier CircuitⅠ Bridge Rectifier Diode CircuitThe bridge rectifier uses four semiconductor diodes to be connected in pairs. When the positive half of the input sine wave is turned on, the two tubes are turned on, and the positive output is obtained; on the contrary, when the negative half of the sine wave is input, the other two tubes are turned on. Since the two tubes are reversely connected, the output is still the positive part of the sine wave. In addition, the utilization efficiency of the input sine wave by the bridge rectifier is twice as high as that of the half-wave rectifier.The rectifier bridge stack is generally used in a full-wave rectifier circuit, and it is divided into a full bridge and a half bridge. The full bridge is composed of 4 rectifier diodes connected in the form of a bridge full-wave rectifier circuit and packaged as a whole. The half bridge is to seal the half of the two diode bridge rectifiers together. Two half bridges can form a bridge rectifier circuit, and a half bridge can also form a full wave rectifier circuit with a center tap of the transformer. When choosing a rectifier bridge, the rectifier circuit and operating voltage must be considered carefully.The forward current of the full bridge has various specifications such as 0.5A, 1A, 1.5A, 2A, 2.5A, 3A, 5A, 10A, 20A, 35A, 50A, etc. The withstand voltage (the highest reverse voltage) is 25V, 50V, 100V, 200V, 300V, 400V, 500V, 600V, 800V, 1000V, etc.In this chapter, the rectifier diode is regarded as an ideal component, that is, its forward conduction resistance is considered to be zero, and its reverse resistance is infinite, because of the convenience of analyzing the rectifier circuit. However, in practical applications, it should be considered that the diode has internal resistance, and the output amplitude of the waveform obtained after rectification will be reduced by 0.6~1V. When the input voltage of the rectifier circuit is large, this part of the voltage drop can be ignored. On the contrary, if the input voltage is small, for example, if the input is 3V, the output is only 2V, and the influence of the diode forward voltage drop needs to be considered.Current Direction of the Bridge Rectifier CircuitFigure 1.In the positive half cycle of u2, D1 and D3 are turned on, D2 and D4 are turned off, and the current returns from the upper end of the TR secondary to the lower end via D1→RL→D3, and a half-wave rectified voltage is obtained on the load RL.In the negative half cycle of u2, D1 and D3 are off, D2 and D4 are on, and the current returns from the lower end of Tr secondary to the upper end of Tr secondary via D2→RL→D4, and the other half-wave rectified voltage is obtained on the load RL. Ⅱ Bridge Rectifier Circuit Features(1) The rectification device used is twice that of full-wave rectification.(2) Rectified voltage pulse changing direction is the same as full-wave rectification.(3) The reverse voltage that each device bears is the peak value of the power supply voltage.(4) The utilization rate of the transformer is higher than that of the full-wave rectifier circuit. Ⅲ Single Phase Rectification vs Three Phase Rectification3.1 Single Phase Bridge Rectifier CircuitFigure 2.The single phase bridge rectifier circuit is composed of four diodes connected in the form of a bridge. Its disadvantage is that it only uses half a cycle of the power supply, and at the same time the rectification voltage has a large pulsation.The above Figure 2 (a) shows the direction of current in the single-phase bridge rectifier circuit. The solid arrow indicates the situation when the AC power supply is in the positive half cycle, and the dotted arrow indicates the situation when the AC power supply is in the negative half cycle.It can be seen that the four diodes are divided into two parts: positive half cycle and negative half cycle. However, the current direction on the load does not change. This is full-wave rectification. In addition, the single-phase bridge rectifier circuit can be implemented with an integrated device "bridge stack" in practice.In Figure 3. shows the waveform diagram of the single phase bridge rectifier circuit. According to the diagram, the average voltage is: Uo ≈ 0.9U2 (where U2 is the effective value of the output voltage of the transformer secondary side).Figure 3. Wave Form (single phase)3.2 Three Phase Bridge Rectifier CircuitFigure 4.The three phase bridge rectifier circuit is developed from a uncontrolled half-wave rectifier circuit, which is essentially a series connection of a set of common cathode and a set of common anode with three semiconductor diodes.In addition, the three phase bridge circuit must have two thyristors turned on at the same time, one in the common cathode area and the other in the common anode area to form a loop.Circuit Analysis LawThe diode with the highest anode potential in the common cathode group is turned on.The diode with the lowest cathode potential in the common anode group is turned on.Circuit Analysis ExamplesFigure 5. t1 ~ t2In the common cathode group, the potential at point U is the highest, and V1 is on.In the common anode group, the potential at point V is the lowest, and V4 is on.The voltage across the load is the line voltage Uuv. Figure 6. t2~t3In the common cathode group, the potential at point U is the highest, and V1 is on.In the common anode group, the potential at point W is the lowest, and V6 is turned on.The voltage across the load is the line voltage Uuw. Figure 7. t3~t4In the common cathode group, the potential at point V is the highest, and V3 is on.In the common anode group, the potential at point W is the lowest, and V6 is turned on.The voltage across the load is the line voltage Uvw.......SummeryIn a full-wave cycle, it can be divided into 6 intervals, each of which is powered by a pair of phase wires to the load.In a full-wave cycle, each diode is turned on for one-third of the time (the conduction angle is 120°).During the 6 periods in a cycle, the voltage of the load can be seen as a periodic change. Ⅳ Role of Bridge Rectification1. Convert the alternating current generated by the alternator into direct current to power the electrical equipment and charge the battery.2. Limit the battery current to flow back to the generator to protect the generator from being burnt out by the reverse current.Figure 8. Bridge Rectifier AC to DC Flow ChartⅤ Bridge Rectifier Wiring DiagramThe bridge rectifier circuit overcomes the shortcomings that the full-wave rectifier circuit requires the transformer secondary to have a center tap and the diode to withstand large reverse voltage, but two diodes are used. With the rapid development of semiconductor devices and low cost today, this shortcoming is not obvious, so bridge rectifier circuits are widely used in practice.It needs to be pointed out that the diode as a rectifier component should be selected according to different rectification methods and load values. If choose improperly, you may not be able to work safely, or even burn the pipe, causing waste.Figure 9. Schematic Diagram of Bridge Rectifier CircuitThe bridge rectifier circuit can also be considered as a kind of full-wave rectifier circuit. The transformer is connected to four diodes according to the method shown in Figure 9. D1～D4 are four identical rectifier diodes connected in the form of a bridge, so they are called bridge rectifier circuits. Using the guiding function of the diode, the secondary output can be directed to the load even in the negative half cycle. It can be seen from the figure that D1 and D2 lead the current through RL from top to bottom during the positive half cycle, and D3 and D4 lead the current through RL from top to bottom during the negative half cycle. In this structure, if the same DC voltage is output, the secondary winding of the transformer needs only half of the winding compared with the full-wave rectification. However, if the same amount of current is to be output, the diameter of the winding should be increased accordingly.Because the output voltage of the rectifier circuit contains larger pulsating components. In order to reduce the pulsation component as much as possible, on the other hand, it is necessary to keep the DC component as much as possible to make the output voltage close to the ideal DC. This measure is filtering. Filtering is usually achieved by using the energy storage effect of capacitors or inductors.Figure 10. Bridge Rectifier Circuit with CapacitorIn this experimental circuit, capacitor filtering is used, that is, a filter capacitor C is connected in parallel with the load resistance RL. The circuit is shown in Figure 11, and the filtered waveform is as shown in the figure below.Figure 11. Full-wave Rectification Filter WaveformThe DC component of the full-wave rectified output voltage (compared to the half-wave) is increased, and the pulsation is reduced, but the transformer needs a center tap, which is troublesome to manufacture, and the rectifier diode needs to withstand high reverse voltage, so it is generally suitable for the low output voltage.Figure 12. Half-wave Rectification Filter WaveformHalf-wave rectification is the most commonly used circuit that uses the unidirectional conductivity of a diode for rectification. Ⅵ Difference between Bridge Rectifier and Full-wave Rectifier Circuit1) Don't need a center tap on the secondary side of the bridge rectifier circuit transformer, but use 2 more rectifier diodes.2) The full-wave rectifier circuit uses less than 2 rectifier diodes, but the secondary side of the transformer should be center-tapped.3) The reverse withstand voltage of the rectifier diode used in the full-wave rectifier circuit is twice that of the bridge rectifier.4) Rectification and full-wave rectification have different requirements for the number of secondary transformers. The former requires only 1 set of coils, while the latter requires 2 sets.5) Rectification and full-wave rectification have different requirements for the secondary current of the transformer, the former is twice the latter. Frequently Asked Questions about Bridge Rectifier Circuit1. What does a bridge rectifier do?A bridge rectifier provides full-wave rectification from a two-wire AC input, resulting in lower cost and weight as compared to a rectifier with a 3-wire input from a transformer with a center-tapped secondary winding. ... Diodes are also used in bridge topologies along with capacitors as voltage multipliers. 2. How does a bridge rectifier convert AC to DC?Bridge rectifiers convert AC to DC using its system of diodes made of a semiconductor material in either a half wave method that rectifiers one direction of the AC signal or a full wave method that rectifies both directions of the input AC. 3. What happens when a bridge rectifier fails?Without capacitor smoothing, when 1 diode fails open in a bridge rectifier, both voltage and current reduce. With capacitor smoothing, when 1 diode fails open in a bridge rectifier, the voltage remains fairly constant but the current increases. 4. Why do we use 4 diodes in bridge rectifier?The bridge rectifier consisting of four diodes enables full wave rectification without the need for a centre tapped transformer. The bridge rectifier is an electronic component that is widely used to provide full wave rectification and it is possibly the most widely used circuit for this application. 5. Why is a bridge rectifier more preferable than a full wave rectifier?Bridge rectifier is driven by a single winding which carries current both cycles in load. ... Full wave is better than bridge in one more aspect i.e. the output DC voltage is slightly higher than bridge. This is because it has only 1 diode drop from AC to DC.

For so many years, tube amplifier has always been a “controversial” component in the electronic field, people are attracted by its premium sound quality but discouraged by its price.   Today we are going to talk about tube amplifiers, to understand what this device is, why its price is so much higher than other amplifiers, what are its advantages and disadvantages compared with other amplifiers, and so on. Catalog I. What is a Tube Amplifier? II. Pros and Cons of Tube Amplifier? III. How Does the Tube Amplifier Work? IV. Tube Amplifier VS Solid State Amplifier? V. Tube Amplifier VS Transistor Amplifier? VI. Things Needing Attention While Using a Tube Amplifier VII. Why is Tube Amplifier So Expensive? Is It Worth It? VIII. How to Extend the Life of   the Tube Amplifier?    FAQ I. What is a Tube Amplifier? The tube amplifier is one of the earliest electrical signal amplifiers.   The cathode electron emission part, the control grid, the acceleration grid, and the anode (panel) lead enclosed in a glass container (generally a glass tube) are welded to the tube base.   The electric field is used to inject an electronic modulation signal into the control grid in the vacuum, and the signal data of different parameters after signal amplification or feedback oscillation is obtained at the anode.   Tube amplifiers were used in electronic products such as televisions and radio amplifiers in the early days. In recent years, they have been gradually replaced by amplifiers and integrated circuits made of semiconductor materials. However, in some high-fidelity audio equipment, tube amplifiers with low noise and high stability coefficient are still used. II. Pros and Cons of Tube Amplifier? Pros: 1. The tube amplifier has a large input dynamic range and a fast conversion rate.   2. Electronic tube amplifiers mostly use discrete components, manual wiring, and welding, which are low in efficiency and high in cost. This is especially obvious in developed countries.   3. The open loop index of the tube amplifier is better than that of the transistor amplifier. It does not need deep negative feedback and can work stably without adding phase compensation capacitors, so its dynamic index is better.   4. The sound quality of the tube amplifier is generally soft and pleasant. More specifically, the low-frequency sound of the tube amplifier is soft and clear, and the high-frequency sound is slender and clean. The performance of human voice is its strong point.   5. The treble of the tube amplifier is smoother, has enough air, and has a sound coloring that quite a few people like. The soft and slightly fuzzy sound is very beautiful.   6. The tube amplifier mainly causes even-numbered second harmonics. This harmonic component is very pleasing, just like adding rich overtones and beautifying the sound.   Cons: 1. The service life of the tube amplifier is relatively low, and some technical indicators will drop significantly after one to two thousand hours of use.   2. The tube amplifier consumes high power and often works in Class A state, which reduces the efficiency. However, there are basically no harmful sound quality factors such as transient intermodulation distortion, switching distortion and crossover distortion.   3. The tube amplifier is not at all superior to the transistor amplifier in terms of weight, efficiency, and lifespan.   4. In use, the tube amplifier should have good ventilation and heat dissipation. Overheating of the temperature will inevitably shorten the life of the tube amplifier, so it is necessary to keep the temperature of the tube amplifier as low as possible.   5. Vibration is not good for tube amplifiers, so it is important to take anti-vibration measures to avoid vibration as much as possible. III. How Does the Tube Amplifier Work? This is a basic overview of some of the components of a tube guitar amp and how they work, without getting too technical. IV. Tube Amplifier VS Solid State Amplifier? A solid-state amplifier converts an electrical signal into an audio wave using transistor circuitry. Instrumental amplifiers have two amplification stages: the preamp stage at the beginning of the circuit and the power amp stage at the end.    The physical difference between a solid-state amp and a tube amp is that a solid-state machine employs electronic transistors for amplification, whereas a tube amp employs vacuum tubes (also known as valves). Transistors differ from tubes in that they do not deform pleasantly when pushed to their limits.   The key difference between tube amplifier and solid state amplifier is: solid-state amplifiers are ideal for guitarists that require a lot of power (a.k.a a loud, clean, undistorted signal). However, without any natural distortion, an electric guitar can sound brittle. As a result, solid-state amplifiers are more popular among bassists and keyboard players than guitarists. Compared with tube amp, solid-state amp has several advantages: 1.    They are less expensive. Almost all solid-state amplifiers are less expensive than tube amplifiers. They have fewer parts and the ones they do have are reasonably inexpensive.  2.    They are less bulky. Weight can be an issue if you're a gigging musician who needs to transport an amp around town. Tube amplifiers are almost always heavier than solid-state amplifiers. This is due to the circuitry necessary to operate the glass tubes, not the glass tubes themselves (which are hollow). 3.    They require less maintenance. Tube amplifiers need routine maintenance. Most gigging guitarists replace their power tubes once a year and their preamp tubes every two years. Solid-state amplifiers, on the other hand, do not require part switching. They can function for decades with all of their original components. V. Tube Amplifier VS Transistor Amplifier? A transistor amplifier, as the name implies, is used to amplify power, voltage, or current signals. It has a common emitter amplifier, a common collector amplifier, and a common base amplifier. This is the most basic. There are also differential, push-pull, and so on. The audio is actually a power (transistor) amplifier. The difference between transistor amplifier and tube amplifier: 1. Working characteristics and circuit structures are different Transistor amplifiers work under low voltage and high currents. The working voltage of transistor power amplifiers is within tens of volts, and the current reaches several amperes or tens of amperes. In the circuit design, direct-coupled (OCL, BTL, etc.) non-output transformer circuits are mostly used. The output power can be very large, up to several hundred watts, and the various electrical properties are very high. The tube amplifier works under high voltage and low current conditions. The screen voltage of the final power amplifier tube can reach 400-500V or even thousands of volts, and the current flowing through the electron tube is only tens of milliamps to hundreds of milliamps. The input range is too large and the conversion rate is fast. Most of the tube amplifiers use discrete components, manual wiring, and welding, which are low in efficiency and high in cost. Transistor amplifiers mostly use a combination of transistors and integrated circuits, and printed circuit boards are widely used, with high efficiency, stable soldering quality, and high electrical performance indicators. 2. Power reserve and anti-overload ability are different The dynamic range of the high-fidelity amplifier should be 120dB, so as to meet the needs of the sound from the slightest to the peak of the climax, the amplifier output is not clipped, so the amplifier must have sufficient power reserve. If the dynamic range of the audio voltage is 3:1, since the power is proportional to the square of the voltage, the power dynamic range is 9:1. That is to say, a power amplifier with a power of 90W can only be turned on to 10W to achieve high-fidelity playback. Therefore, the transistor amplifier needs a large power reserve to avoid overload distortion. Once the ground is loaded, its distortion will almost rise in a vertical line, which can damage the transistor in severe cases. The anti-overload capability of the tube amplifier is far stronger than that of the transistor amplifier. In case of overload, the peak of the music signal only becomes slippery than the normal waveform, and the sound is not deformed much. For transistor amplifiers, clipping will occur at this time, and the sound quality will deteriorate significantly. 3. Efficiency, life, and cost are different Tube amplifiers are not superior to transistor amplifiers in terms of weight, efficiency, and lifespan. The service life of the electron tube is relatively low, and some technical indicators will drop significantly after one to two thousand hours of use. The lifetime of transistors and integrated circuits is much longer. In addition, the tube amplifier consumes high power and often works in the Class A state, which reduces the efficiency. However, there are no harmful sound quality factors such as transient intermodulation distortion, switching distortion, and crossover distortion. In terms of cost, for the same grade of amplifiers, tube amplifiers are generally significantly higher than transistor amplifiers. The main reasons are the high cost of electronic tubes and output transformers, and the production process of electronic tube power amplifiers is not easy to automate, and the production efficiency is low. 4. Different sound quality The sound quality of the tube amplifier is significantly better than that of the transistor amplifier. Transistor power amplifiers have a sense of overwhelming when listening to high and medium and high frequencies, and less low frequencies. Transistor power amplifiers sound hard, especially low-frequency sounds are not soft enough, and high-frequency sounds are sharp and dry. Sometimes it sounds like there is crossover distortion in the high-frequency range. These phenomena become more obvious when the frequency increases and the volume is louder. However, the transistor amplifier has large dynamics and high speed, which is especially suitable for music with greater dynamics. As for the sound effects of guns and lightning, it is certainly better than a tube amplifier. Generally speaking, the sound quality of the tube amplifier is soft and pleasant. Specifically, the low-frequency sound of the tube amplifier is soft and clear, and the high-frequency sound is slender and clean. The performance of the human voice is its strong point, and therefore it is more valuable. All in all, the choice of amplifier varies from person to person. If you like orchestral music, especially chamber music and vocals, then tube amplifiers should be your first choice. If you like jazz, rock, and modern music, then transistor amplifiers are the choice. VI. Things Needing Attention While Using a Tube Amplifier? 1.    The tube amplifier must be used under the limit parameters. Although it can still work normally under the limit parameters, the life of the tube amplifier will be shortened quickly. Therefore, the tube should be used under the rated parameters. 2.    The location of the components in the device should be conducive to the heat dissipation of the tube amplifier. To control the temperature of the tube case of the tube amplifier, the allowable temperature of the glass case of various tube amplifiers is different. For example, the allowable limit temperature of the power output tube during operation does not exceed 90°C in principle. 3.    Except for the high-reliability tube amplifier with a special structure that can work at higher accelerations, other receiver amplifier tubes can only withstand small shocks for a short time. Therefore, pay attention to the shock absorption of the tube when using it. 4.    When using small tubes (thumb-finger type) and other tubes without tube bases (but with tube needles), use tube sockets specified by the Ministry of Electronics Industry. Prevent cracking or damage to the glass shell. When plugging and unplugging the tube, its direction should be perpendicular to the plane of the tube base. When inserting an electronic tube, prevent damage to the normal position of the contact reed in the socket socket of the tube socket, and avoid using the empty foot of the tube socket as a connecting pad. 5.    When using an indirectly heated tube amplifier, the potential difference between the cathode and the filament must not exceed the specified limit. For this reason, a dedicated filament transformer is often used for power supply. In order to eliminate the effect of leakage current instability, under the condition of not hindering the operation of the circuit, a shunt resistance of about several ohms can be connected between the cathode and the filament. VII. Why is Tube Amplifier So Expensive? Is It Worth It? In short, tube amplifiers are costly because they use pre and power tubes as their primary amplification source. Each tube costs approximately $50 and can have up to four of them in a single unit. Second, these amplifiers have more expensive components, larger casings, and more complicated circuitry than solid-state amplifiers.   Whether tube amplifiers are "worth it” or not, well, that’s more of a subjective question.   If your goal is to build a pristine audio chain that cleanly reproduces the input signal you give it, a tube amplifier is definitely not worth it. By spending extra money to put a tube in your signal chain, you are intentionally distorting the sound.   Note that modern high end A/D/A conversion equipment (which aims for perfect signal reproduction) never uses tubes. The marketing pitch on tube equipment is that it does change the sound that you give it. Don't buy a tube amplifier unless that is what you want.   Now, if your goal is not to amplify signal accurately, but rather to make a sound that you personally find pleasing, a tube may yield some benefits.   You can listen to some tube amps at different levels to decide what you personally prefer. Does this make a tube amp worth it? Bear in mind that there are many ways of creating harmonic distortion (in the analog domain, or emulated with digital techniques), and many are cheaper than tubes, which are expensive to produce.   The high cost of tubes is not a function of the fact that it was difficult to engineer their particular audio qualities. The way tube amplifiers color audio is a historical function of the fact that engineers were not able to compensate for the changes they introduce.   Many people have now decided that this is a valuable property - but the production of tubes is becoming relatively more expensive as demand for them diminishes and they require specialty, limited-run manufacturing (compared to transistors, demand for which is growing).   In all, thinking from your practical needs before jump into any conclusion, whether tube amplifier is worth it or not, there’s no absolute answer to this question. VIII. How to Extend the Life of the Tube Amplifier?    The problem of short life of the tube amplifier is often criticized, but this is often not a problem of the tube amplifier itself, but a defect in the circuit design and a problem in use. It should be noted that a good quality tube amplifier must have a correctly designed circuit, sufficient heat dissipation, and thoughtful shock absorption.   In use, the tube amplifier must have good ventilation and heat dissipation. Overheating of the temperature will inevitably shorten the life of the tube, so the tube amplifier should be kept as low as possible.   Vibration is not good for tube amplifiers, so it is important to take anti-vibration measures to avoid vibration as much as possible. If these two can be achieved, the service life of the tube amplifier can be at least doubled. For this reason, there should be a proper space around the tube amplifier equipment, especially above it, in order to have good convection ventilation, if possible, a fan can be used to help dissipate heat.   When the cathode of the tube amplifier has not reached the required temperature, the high-voltage power supply is immediately applied, and its cathode will be damaged, which will also shorten the life of the tube amplifier.   Therefore, if the tube amplifier equipment has a preheating device, it must be used. For example, first turn on the filament low-voltage power supply to preheat, and then turn on the high-voltage power supply. If there is no preheating device, don't rush to connect the input signal, you can turn the volume down to the minimum, wait for 20-30 minutes to warm up the machine before using it.   If the indirectly heated rectifier tube is used to supply the high voltage of the whole machine, it just provides a simple and effective high voltage delay. In addition, do not switch the power supply frequently during normal use.   Of course, if the tube amplifier circuit is designed correctly and the wrong use is avoided, the tube amplifier will not "die young". It should be normal for the tube amplifier to use thousands of listening hours.   The most common mistakes in circuit design are: 1. The potential difference between the filament and the cathode of the tube amplifier is too high 2. The screen or screen grid voltage of the tube amplifier is applied to the maximum value 3. The filament voltage of the tube amplifier is too low or too high 4. Improper installation position of the tube amplifier causes the electrode to overheat and the high-voltage power supply does not have a delay device, etc.   Therefore, these problems should be avoided when designing the circuit to effectively extend the service life of the tube amplifier. FAQ 1. Why is a tube amp better? Tubes, like analog recordings, have a more full-bodied sound than transistor gear. There's a "roundness" to tube sound that solid-state gear never equals. Tubes are less forgiving about mismatches, so to get the best out of a tube amp it must be used with just the right speaker. 2. What is tube amplifier used for? Tube amplifiers, or tube amps as they're commonly called, are tiny electronic or electromagnetic components that are used to boost electric current in devices to improve their performance. It's what makes your hearing aid pick up sounds through a microphone from all around you. 3. Are tube amps worth it? In many cases, tube amps do not require the amount of maintenance that they have a reputation for. As long as you properly take care of your gear, owning a tube amp is simple and very well worth it for the tone. 4. How long should a tube amp warm up? 20 to 30 minutes. As a rule of thumb, your tube amp needs to be warmed up for 20 to 30 minutes at least before you can start playing your guitar. 5. Why are tube amps louder? When tubes are driven outside their linear region, for the first 12db or so of overdrive the harmonics that they produce trick the human ear into thinking that the sounds are getting louder, when in fact the sound is getting progressively more distorted. 6. How does a tube amplifier work? The power transformer and rectifier work together as an electron pump which pulls electrons out of the amp circuit creating a positive voltage (electron scarcity = positive voltage). The amplifier's electronics need DC to amplify. The amp is powered by DC but the guitar signal moving through the amp is AC. 7. What's the difference between a tube amp and a regular amp? The physical difference between a solid-state amp and a tube amp is that a solid-state machine derives amplification from electronic transistors, while a tube amp uses vacuum tubes (also known as valves). ... Solid-state amps are great for players who want maximum headroom (a.k.a a loud, clean, undistorted signal). 8. Which is better tube amp or solid state? Tube amps are generally more expensive in initial cost and to operate (because you need to replace the tubes occasionally), and solid-state amps are generally less delicate and more reliable. Many players, however, feel that tube amps yield a warmer, more musical tone and more musical-sounding distortion. 9. How often should a tube amp be serviced? 15 years. If its a well made amp, recap every 10 or 15 years, retube as needed. Fenders might go many years without needed a power tube replaced. 10. How many watts do I need in a tube amp? 100 watts. You'll need a solid state amp that has around 100 watts, or a valve amp that has around 50 watts. This will usually give you enough volume that you can be heard over the drummer, without having to push your amp's volume too hard so that the distortion becomes overbearing.

IntroductionUSB is very common, because it is indispensable for data transmission and charging. In modern life, we can see one or more USB ports on desktop computers, laptops, TVs, game devices, cars, media players, phones, and other electric devices, etc. USB devices are very important for our life. Look at your computer or smart phones, we probably know what it used for, however, fewer people know the full name of USB and what the real meanings of USB protocols and USB types.USB Ports, Cables, Types, & ConnectorsCatalogIntroductionⅠ Figure USB Ports and Standards OutⅡ USB Port Colors MeaningⅢ USB-C vs Type CⅣ USB 2.0 vs USB 3.0Ⅴ According to Labels Behind USB PortsHere are some easy steps to identify USB ports with different standards.Ⅰ Figure USB Ports and Standards OutUSB (universal serial bus) aims for input and output interfaces standard. It is widely used in information transformation products such as personal computers and mobile devices. The USB interface has hot-swappable, plug-and-play functions, and can be connected to a variety of external devices, such as a mouse and keyboard, etc. Our mobile phone charging uses the USB connector. These USB devices give us great convenience. USB chargers, USB connectors, USB hub, USB ports and USB cables, are all USB the same? What is USB 2.0 and USB 3.0? Low speed, full speed, and high speed mean what? What are Type-A, Type-B, and Type-C? Here you will get a full answer.Versions of USBThe USB 1.0/2.0/3.0 we often say refers to the technical specifications. The biggest difference among them is speed, that is, they indicate the speed of USB transfer files. The maximum transmission bandwidth of USB 3.0 is up to 5.0Gbps (640MB/s). Now many high-speed U disks or hard drives of portable electric devices use USB 3.0 or USB 3.1. USB also includes the old USB 1.1 standard and  USB 2.0 standard. The traditional maximum transfer rate of USB 1.1 is 12Mbps. Generally, manufacturers call its products that comply with the USB 1.1 standard as "full-speed USB." When the high-speed USB 2.0 was first introduced, the highest transmission rate was only 240Mbps. Later, the USB Promoter Group increased the rate to 480Mbps in October 1999, which is 40 times faster than the traditional USB 1.1. USB 2.0 is backward compatible with USB 1.1. Of course, USB 1.1 devices are "upward compatible" with USB 2.0, but they cannot reach the transmission speed of USB 2.0 and automatically stay at low speed. The maximum length of the USB 2.0 cable is 5 meters, but if five USB adapters are used, the maximum length can be up to 30 meters.Although you'll still be able to connect old-school devices with USB Type-A or USB Type-B connectors, but now you have more choices, that is USB4. USB4 is a USB system specified in the USB4 specification which was released in version 1.0 on 29 August 2019 by USB Implementers Forum. It leverages the Thunderbolt 3 protocol to deliver speeds up to twice as fast as the USB version it replaces. The USB4 architecture defines a method to dynamically share a single high-speed link with multiple end device types to best serve the transfer of data by type and application. USB-A, USB-B, and USB-C Port Types-Which is faster?Type-A/B/C determines the appearance of the USB ports. For example, the mouse, keyboard, USB flash drive and other interfaces we use are generally Type-A, which is also the most widely used interface. Type-B is more common in printers, monitors and other devices. In the past, Micro USB and Mini USB commonly used in mobile phones were portable versions of USB 2.0. The appearance of Type-C is very recognizable, slimmer. Its biggest feature is flippability, that is, USB-C connector has no up or down orientation, so you never have to flip it over to plug it in.1) Type-A: Standard USB PortType-A is the most common types of USB ports on computers. It has a notable feature: direction requirements. The connector (male port) must be inserted into the interface (female port) from a certain direction, in addition, because the appearance of the two sides of the USB male port is very close, this insertion process often makes mistakes.2) Type-B: Commonly used in printer equipmentType-B is the most common and popular data interface type on printers and displays, and some displays will also use it.3) Type Micro-B: USB standard for mobile devicesCurrently, most Android phones use the Micro USB interface (USB Micro-B), which is still widely used in various mobile portable devices.4) Type-C: It will become mainstreamAlthough Type-C has just appeared, it is foreseeable that as the USB Type-C technology matures, various notebooks, tablets and even smart phones in the future will begin to use the USB Type-C interface. Ⅱ USB Port Colors MeaningColorUSB ConnectorUSB Speed StandardNoteWhiteUSB-A or USB-B  Micro USB-AUSB 1.0 or USB 1.1*BlackUSB-A or USB-B Micro USB-BUSB 2.0 Hi-Speed*BlueUSB-A or USB-BUSB 3.0 Super Speed*RedSleep-and-Charge USB-AUSB 3.1 Gen 2 USB 3.2Usually denotes an "always on" portYellowSleep-and-Charge USB-AUSB 2.0 or USB 3.0Higher power or "always on" portⅢ USB-C vsType CThe Type-C is the same as the USB C, because the USB C is also called USB Type-C. However, there are slight differences between them. Let’s look at the following facts.Features of USB-C Connector:1. Ultra-thinThe old USB port size is 14mm * 6.5mm, while the USB-C is only 8.4mm * 2.6mm.2. No OrientationLike the Lightning, there will be no problem regardless of whether it is plugged in or reversed. It claims to be able to up to 10,000 times of repeated plugging and unplugging.3. Fast Transfer RateThe maximum transfer rate of the USB-C port is 10Gb per second, which is much faster than USB 3.0.4. Two-way TransmissionUnlike the old USB port, the power can only be transmitted in one direction. The USB-C port is bidirectional, so it can have two transmission power ways. Therefore, users can not only use laptops to charge mobile devices, but also use other devices or mobile power sources to charge laptops.5. Strong Power Supply CapabilityThe standard specification cable equipped with Type-C connector can pass 3A current, and it also has a super USB power supply capacity, which can up to 100W of power.6. Backward CompatibilityUSB-C can be compatible with the old USB protocol, but users need an additional adapter.USB-C refers to the Type C port that uses the USB 3.1 standard, but it should be noted that USB-C is not equal to Type C. Because there are many Type C devices that can only reach USB 2.0 or USB 3.0 transfer rate.With the improvement of technology, Type-C also supports the USB3.1 standard. Because the voltage and current increase, the coding consumption is reduced, from 20% of USB 3.0 to 3%. In other words, users can quickly transfer data and video through Type-C, or charge faster. Also users can charge other devices with their mobile phones. As for the display, when using Type-C for data transmission, there is no need to use another power cord to power the display, which solves the problem of messy desktop cables. Even the relatively high-end HDMI and DP ports cannot do it.The USB-C connector can be expanded into three: power supply/ USB transmission/ VGA or HDMI, which is the next-generation mainstream USB interface. The type-c cable is also of great help to the arrival of the 5G. Because the port of it becomes smaller, the flattening of electronic products is promoted. And in the transmission of audio and video, the tc data line has faster speed. At present, well-known technology manufacturers such as Sony and Apple have widely used type-c cables on their electrical devices because they can support multiple formats and reduce the limitations of USB. In short, the arrival of the 5G actually wants everyone to experience faster bandwidth, so the corresponding supporting facilities should also keep up. The type-c cable is undoubtedly one of them. Ⅳ USB 2.0 vs USB 3.0Although USB has developed to the USB3.1 protocol, we often see two types of USB 2.0 and USB 3.0 on devices. How do we distinguish these two interface types in daily use? Some people will say that USB 3.0 port is blue and USB2.0 port is black, which is easy to distinguish. In fact, it is not. Even though most USB3.0 ports use blue, there are many special cases. Here are some examples. The color of the USB ports on some models does not have any special treatment, and it looks no different from USB 2.0 type, and it is all black. However, it is often marked with "SS" in front of the logo. "SS" is the abbreviation of "SuperSpeed USB", which means connector or port that uses the USB 3.0 standard. The black USB type is also suitable for USB 3.0. The USB ports in Apple's new MacBook notebooks are all USB 3.0 standard, but in order to keep in harmony with the color of the computer cover, a white connector design is adopted. The USB ports on the Razer gaming notebooks are also USB 3.0, but in order to match the bright green keyboard backlight on the body and the Razer logo, the color of the USB port adopts "green". It improves the recognition of the machine and the brand, because no third-party manufacturer has adopted a green USB interface design. In addition, distinguish the metal pins of the USB ports. Generally, USB 2.0 uses a row of 4 pins, while USB 3.0 has a two-row pin design, with 5 pins in the front row and 4 pins in the back row. In addition, there is also a hybrid port of eSATA and USB 2.0, which can plug in both USB devices and eSATA interface devices. However, they are common in business models of previous years. Ⅴ According to Labels Behind USB Ports"+" sign - It represents the USB interface with high current output capability. The ordinary USB interface provides a maximum current of 500mA, but it may not be able to drive when encountering "high energy consumption" devices such as mobile hard disks and USB optical drives. Therefore, when it appeared, the output current on this interface can reach 1000mA (1A), which greatly enhances the drive capability."SS" - It is actually a symbol of USB 3.0. If the USB port has “SS” (or “SuperSpeed”) on its label, it’s a USB 3.0 port. If it’s“SS 10”, it’s a USB 3.1 port."Lightning Logo" -It generally appears on notebooks, and the USB port with it has a power-off charging function. That is, it can use its own battery or an external power supply to charge the mobile device when it is turned off. The lightning mark with an arrow indicates the Thunderbolt 3: two-way charging and two-way data transmission. Thunderbolt 3 supports for up to 40Gbps of throughput, alongside reduced power consumption and the ability to move as much as 100 watts of power over the interface. And it also means that a single cable is all you need to push power and transfer a large amount of information (up to and including video data for two 60Hz 4K displays) to and from even a complex device like a computer, something many laptop manufacturers have been quick to take advantage of.USB is an important interface on the computer. Almost 90% of the external devices are connected by it for mobile hard drives, such as U disks, printers, etc. Understanding the above information can analyze and solve the most common problems of unrecognized external devices of USB. At the same time, it is also very useful for us to choose USB products. Ⅵ Frequently Asked Questions about USB Types and USB Versions1. What are the different types of USB ports?Types of USB Ports and ConnectorsUSB-AUSB-BUSB-B MiniUSB-B MicroUSB-CLightning 2. How can I tell the difference between USB 2.0 and 3.0 ports?You can generally tell the difference between USB 1.0, 2.0, and 3.0 by color alone. While the size and shape may be identical, the key is to look at the color of the plastic inside the device. The USB 1.0 features a white plastic color, while USB 2.0 is black, and the USB 3.0 is blue. 3. What is the difference between USB Type A and C?The USB-A has a much larger physical connector than the Type C, Type C is around the same size as a micro-USB connector. ... The beauty of Type C is that it can be inserted any way up as the connector pins are the same on either side. 4. Are USB 2.0 and 3.0 ports the same?The A connectors still work properly so any 2.0 device with a 2.0 cable can be used with 3.0 ports or hubs. To sum up: USB 3.0 devices require 3.0 cables. ... USB 2.0 cables can be used with 3.0 ports but the transfer rate will fall back to 2.0. 5. Why is my USB 3.0 port not working?Update to the Latest BIOS, or Check USB 3.0 is Enabled in BIOS. In many cases, your motherboard will be responsible for software issues related to your USB 3.0 ports or any other ports on the motherboard. For this reason, updating to the latest BIOS may fix things.

In this article, we will present you a comprehensive introduction to solid state relay, covers from its definition, characteristics, structure, pros and cons, and some problems you might encounter with during using SSR and so on. Catalog I. What is a Solid State Relay? 1.1 Brief Introduction 1.2 Structure of Solid State Relay 1.3 Characteristics of Solid State Relay 1.4 Difference Between Solid State Relay & Normal   Relay II. Pros and Cons of Solid State Relay III. Common Problems of Solid State Relays IV. Maintenance Method of Solid State Relay V. Application of Solid State Relay FAQ I. What is a Solid State Relay? 1.1 Brief Introduction The solid state relay (SSR) is a non-contact switch composed of microelectronic circuits, discrete electronic devices, and power electronic power devices. It is a component of a full electronic circuit combination. It depends on the electromagnetic and optical characteristics of semiconductor devices and electronic components. Its isolation and relay switching functions.   This video tells briefly what solid state relay is. Compared with the traditional electromagnetic relay, the solid-state relay is a relay without machinery and no moving parts, but has essentially the same functions as the electromagnetic relay.   Solid state relays are widely used in industrial automation control, such as electric furnace heating systems, familiar control machinery, remote control machinery, motors, solenoid valves and signal lights, flashers, stage lighting control systems, medical equipment, photocopiers, washing machines, fire protection systems, etc. It works reliably, has no contact, no spark, long life, no noise, no electromagnetic interference, fast switching speed, and achieves the purpose of directly driving a large current load with a tiny control signal. 1.2 Structure of Solid State Relay The solid state relay is composed of three parts: input circuit, isolation (coupling) and output circuit.   1. Input circuit: According to the different types of input voltage, the input circuit can be divided into three types: DC input circuit, AC input circuit and AC/DC input circuit. Some input control circuits are also compatible with TTL/CMOS, positive and negative logic control and inverting functions, and can be easily connected with TTL and MOS logic circuits.   For a control signal with a fixed control voltage, a resistive input circuit is used. The control current is guaranteed to be greater than 5mA. For the control signal with a large variation range (such as 3~32V), a constant current circuit is used to ensure reliable operation of the current greater than 5mA within the entire voltage variation range.   2. Isolation and coupling The input and output circuits of solid state relays can be isolated and coupled in two ways: photoelectric coupling and transformer coupling: photoelectric coupling usually uses photodiodes-phototransistors, photodiodes-bidirectional light-controlled silicon controlled thyristors, photovoltaic cells, to achieve control side and load side Isolation control; high-frequency transformer coupling is a self-excited high-frequency signal generated by the input control signal is coupled to the secondary, detected and rectified, and processed by a logic circuit to form a drive signal.   3. Output circuit The power switch of the SSR is directly connected to the power supply and the load side to realize the on-off switching of the load power supply. Mainly use high-power transistors, unidirectional thyristors (or SCR), bidirectional thyristors (Triac), power field effect transistors (MOSFET), and insulated gate bipolar transistors (IGBT).   The output circuit of solid state relay can also be divided into DC output circuit, AC output circuit and AC/DC output circuit. According to the load type, it can be divided into DC solid state relay and AC solid state relay. Bipolar devices or power FETs can be used for DC output, and two thyristors or one bidirectional thyristor are usually used for AC output. The AC solid-state relays can be divided into single-phase AC solid-state relays and three-phase AC solid-state relays. AC solid-state relays can be divided into random AC solid-state relays and zero-crossing AC solid-state relays according to the timing of turn-on and turn-off. 1.3 Characteristics of Solid State Relay The solid state relay is a non-contact electronic switch with isolation function, and there are no mechanical contact parts during the switching process. Therefore, in addition to the same functions as electromagnetic relays, solid state relays also have logic circuit compatibility, vibration resistance and mechanical shock resistance, unlimited installation location, and good moisture, mildew and corrosion resistance. It also has excellent performance in explosion protection and prevention of ozone pollution. It also has the characteristics of low input power, high sensitivity, low control power, good electromagnetic compatibility, low noise and high operating frequency.   (1) The SSR has no internal mechanical parts, and the structure adopts a fully sealed method of perfusion. Therefore, the SSR has the advantages of vibration resistance, corrosion resistance, long life and high reliability, and its switch life is up to 10.1 million times; (2) Low noise: AC SSR adopts zero-crossing trigger technology, so the voltage rise rate dv/dt and current rise rate di/dt value are effectively reduced on the line, so that the SSR has minimal interference to the mains during long-term operation; (3) Its switching time is short, about 10ms, which can be used in higher frequency occasions; (4) It adopts photoelectric isolation between its input circuit and output circuit, and the insulation voltage is above 2500V; (5) Its input power consumption is very low, compatible with TTL and COMS circuits; (6) Its output terminal has a protection circuit; (7) Strong load capacity. 1.4 Difference Between Solid State Relay & Normal Relay Ordinary relays are generally composed of relay coils and static and dynamic contacts. The movable contact is actuated by the electromagnetic attraction force of the relay coil to realize the connection and disconnection of the circuit. So there is mechanical movement. When the current reaches a certain level, the contacts will spark. Ordinary relays are cheap and simple in structure, but sparks and mechanical movements during operation will have a certain impact on its life.   The advantages of ordinary relays are: simple drive, good isolation, and good short-term overload tolerance. The disadvantages of ordinary relays are: large size (heavy), slow response speed (up to ms level), and large power consumption to drive the relay.   The comparison between traditional relays and solid-state relays, as there are many types involved, the following is a comparison between electromagnetic relays and corresponding solid-state relays to illustrate their differences:   1. Structural difference: Electromagnetic relays work by using the suction force generated by the circuit in the input circuit between the electromagnet core and the armature; solid-state relays use electronic components to perform their functions without mechanical moving components, and the input and output are isolated.   2. Difference in working mode: Electromagnetic relay uses the principle of electromagnetic induction to control the on-off of the circuit through the power of electromagnet. Therefore, when DC is used to connect the coil, the contacts can pass AC and DC; solid state relays rely on the electrical, magnetic and optical characteristics of semiconductor devices and electronic components to complete their isolation and relay switching functions. Therefore, they are divided into DC input-AC output type and DC Input-branch output type, AC input-AC output type, AC input-DC output type.   3. Differences in working status: Electromagnetic relays make use of the suction force generated between the armature to make and break the circuit. Therefore, the action response is slow, noisy, and life is limited; solid state relays have fast response, operate without noise, and have a long life.   4. Operating environment: In the influence of temperature, humidity, atmospheric pressure (altitude), sand and dust pollution, chemical gas and electromagnetic interference, electromagnetic relays are generally inferior to solid state relays.   5. Electrical performance difference: Compared with the corresponding solid-state relay, the electromagnetic relay is simple to drive, but has large power consumption, good isolation, good short-term overload tolerance, and is not as good as the latter in high-current and high-power situations. And when controlling the circuit with frequent action, the life of the electromagnetic relay is not as long as the latter.   In short, traditional relays and solid state relays have their own advantages. The latter is more and more popular because of its reliable operation, no contacts, no sparks, long life, no noise, no electromagnetic interference, and fast switching speed.   II. Pros and Cons of Solid State Relay Pros: (1) Long life and high reliability: SSR has no mechanical parts and solid components to complete the contact function. Because there are no moving parts, it can work in a high impact and vibration environment. Because of the components that make up the solid state relay The inherent characteristics determine the long life and high reliability of solid state relays.   (2) High sensitivity, low control power, and good electromagnetic compatibility: The solid state relay has a wide input voltage range and low drive power, and is compatible with most logic integrated circuits without the need for buffers or drivers.   (3) Fast switching: Because solid-state relays use solid-state devices, the switching speed can range from a few milliseconds to several microseconds.   (4) Electromagnetic interference: The solid state relay has no input "coil", no arc ignition and rebound, thus reducing electromagnetic interference. Most AC output solid state relays are a zero-voltage switch, which is turned on at zero voltage and turned off at zero current, reducing the sudden interruption of the current waveform, thereby reducing the switching transient effect.   Cons: (1) After the solid state relay is turned on, the tube voltage drop is large, and the forward voltage drop of the thyristor or two-phase thyristor can reach 1~2V, and the saturation voltage drop of the high-power transistor is also between 1~2V. Generally, the on-resistance of the power FET is also larger than the contact resistance of the mechanical contacts.   (2) The semiconductor device can still have a leakage current of several microamperes to several milliamperes after it is turned off, so ideal electrical isolation cannot be achieved.   (3) Due to the large pressure drop of the tube, the power consumption and heat generation after the turn-on are also large, the volume of the high-power solid-state relay is much larger than the electromagnetic relay of the same capacity, and the cost is also higher.   (4) The temperature characteristics of electronic components and electronic circuits have poor anti-interference ability and poor radiation resistance. If effective measures are not taken, the working reliability of solid state relays will be reduced.   (5) Solid state relays are more sensitive to overload and must be protected by fast fuse or RC damping circuit. The load of the solid state relay is obviously related to the ambient temperature. As the temperature rises, the load capacity will drop rapidly. III. Common Problems of Solid State Relays When the solid state relay is open and there is voltage at the load terminal, there will be a certain amount of leakage current at the output terminal. Care should be taken to prevent electric shock when using or designing. When solid state relays fail to be replaced, products with the same original model or technical parameters should be used as much as possible to match the original application circuit to ensure the reliable operation of the system. Among all, overheat, overcurrent and overvoltage are always the common problems you might encounter when using a solid state relay.   overheat When the SSR is turned on, the component will withstand the dissipation power of P=V (tube pressure drop) × I (load), where the effective value of V and the effective value of I are the effective values of the saturation voltage drop and the operating current, respectively.   The load capacity of the solid state relay is greatly affected by the ambient temperature and its own temperature rise. It must be based on the actual working environment conditions and strictly refer to the allowable case temperature rise (75°C) at the rated working current. Reasonably select the size of the radiator or reduce the current for use. During installation and use, ensure that it has good heat dissipation conditions, otherwise it will cause loss of control due to overheating, and even cause product damage.   Generally speaking, under 10A, an instrument base plate with good heat dissipation conditions can be used, and a product with a rated working current above 10A should be equipped with a radiator.   Below 30A, use natural air cooling. When the continuous load current is greater than 30A, the instrument fan must be used for forced air cooling. Products above 100A should be equipped with a radiator and a fan for forced cooling.   When installing, pay attention to the good contact between the bottom of the relay and the radiator, and consider applying a proper amount of thermal grease to achieve the best heat dissipation effect.   For example, when the relay is working at high temperature for a long time (40℃~80℃), the user can consider derating according to the curve data of the maximum output current and ambient temperature provided by the manufacturer to ensure normal operation.   Reasons for overheating of solid state relays: When the solid state relay is working normally, there is a certain power loss on its internal chip. This power loss is mainly determined by the product of the output voltage drop of the solid state relay and the load current, and is consumed in the form of heat.   Therefore, the quality of heat dissipation directly affects the reliability of the solid state relay, and the excellent thermal design can avoid failure and damage caused by poor heat dissipation.   Overcurrent and overvoltage When the relay is in use, the internal output thyristor of the SSR solid state relay will be permanently damaged due to overcurrent and load short circuit. You can consider adding a fast fuse and an air switch to the control loop for protection (the product output protection should be selected when selecting the relay, built-in Varistor absorption circuit and RC buffer can absorb surge voltage and improve dv/dt tolerance).   Fast fuse and air switch are general overcurrent protection methods. Fast fuse can be selected according to 1.2 times of rated working current, generally small capacity fuse can be used. Pay special attention to load short circuit, which is the main cause of damage to SSR products.   For inductive and capacitive loads, in addition to the internal RC circuit protection, it is recommended to use a varistor in parallel at the output as a combined protection. The area of the metal zinc oxide varistor (MOV) determines the absorption power, and the thickness determines the protection voltage value.   For AC 220V SSR, select MYH12-430V varistor; 380V select MYH12-750V varistor; for larger capacity motor transformer, select MYH20 or MYH2024 varistor with large current capacity. The selection principle is to use 500V-600V varistors for 220V, and 800V-900V varistors for 380V. IV. Maintenance Method of Solid State Relay 1. When selecting solid state relays used on printed circuit boards with low current specifications, since the lead terminals are made of high thermal conductivity materials, the soldering should be carried out under the conditions of a temperature less than 250℃ and a time less than 10S. If the surrounding temperature is considered, If necessary, derating can be considered. Generally, the load current should be controlled within 1/2 of the rated value.   2. Selection of solid state relays for various load surge characteristics   The controlled load will generate a large inrush current at the moment of switching on. Because the heat is too late to dissipate, it is likely to damage the SSR's internal thyristor.   Therefore, the user should analyze the surge characteristics of the controlled load when selecting the relay, and then select the relay. The relay can withstand this surge current under the premise of ensuring steady-state operation. When selecting, refer to the derating factor of various loads in Table 2 (at normal temperature).   If the selected relay needs to work in the occasions with more frequent work, high life and reliability requirements, it should be multiplied by 0.6 on the basis of Table 2 to ensure reliable work.   Generally, follow the above principles when selecting, and when low voltage requires low signal distortion, you can choose a DC solid-state relay that uses a field effect tube as an output device; for example, for AC resistive loads and most inductive loads, you can choose a zero-crossing relay. Extend the life of loads and relays, and also reduce their own radio frequency interference. For phase output control, random solid state relays should be used.   3. The influence of ambient temperature   The load capacity of solid state relays is greatly affected by the ambient temperature and its own temperature rise. During installation and use, ensure that it has good heat dissipation conditions. Products with a rated operating current of more than 10A should be equipped with a radiator, and products with a rated operating current of more than 100A should be equipped with a radiator. Equipped with a radiator and a fan for forced cooling. When installing, pay attention to the good contact between the bottom of the relay and the radiator, and consider applying a proper amount of thermal grease to achieve the best heat dissipation effect.   For example, when the relay is working at high temperature for a long time (40℃~80℃), the user can consider derating according to the curve data of the maximum output current and ambient temperature provided by the manufacturer to ensure normal operation.   4. Overcurrent and overvoltage protection measures   When the relay is used, the internal output thyristor of the SSR solid-state relay will be permanently damaged due to overcurrent and load short-circuit. Consider adding a fast fuse and air switch to the control loop to protect it (the product output protection should be selected when choosing the relay, built-in Varistor absorption circuit and RC buffer can absorb surge voltage and improve dv/dt tolerance); RC absorption circuit and varistor (MOV) can also be connected in parallel at the output of the relay to achieve output protection. The selection principle is to use 500V-600V varistors for 220V, and 800V-900V varistors for 380V.   5. Relay input circuit signal   When in use, when the input voltage is too high or the input current is too large and exceeds its specified rated parameters, consider connecting a voltage divider resistor in series at the input end or a shunt resistor in parallel at the input port, so that the input signal does not exceed its rated parameters value.   6. In specific use, the control signal and load power supply should be stable, and the fluctuation should not be greater than 10%. Otherwise, voltage stabilization measures should be taken.   7. Keep away from electromagnetic interference and radio frequency interference sources during installation and use to prevent the relay from malfunctioning and out of control.   8. When the solid state relay is open circuit and there is voltage at the load terminal, there will be a certain amount of leakage current at the output terminal. Pay attention to it when using or designing.   9. When the solid state relay is replaced by failure, try to choose the product with the same original model or technical parameters to match the original application circuit to ensure the reliable operation of the system. V. Application of Solid State Relay The dedicated solid-state relay can have short-circuit protection, overload protection and overheat protection functions, and the combination logic solidification package can realize the intelligent module required by the user, which can be directly used in the control system.   Solid state relays have been widely used in: (1) Computer peripheral interface equipment, constant temperature system, temperature adjustment, electric furnace heating control, motor control, numerical control machinery, remote control system, industrial automation device; (2) Signal light, dimming, flasher, lighting stage lighting control system; (3) Instruments, medical equipment, photocopiers, automatic washing machines; (4) Automatic fire-fighting, security systems, as well as the switch of power capacitors for power factor compensation of the power grid, etc. In addition, solid state relays are widely used in chemical, coal, and other occasions that require explosion-proof, moisture-proof, and corrosion-proof. FAQ 1. What is solid state relay and how it works? A solid state relay (SSR) is an electronic switching device that switches on or off when an external voltage (AC or DC) is applied across its control terminals. It serves the same function as an electromechanical relay, but has no moving parts and therefore results in a longer operational lifetime. 2. What is the difference between a relay and a solid state relay? The main difference between solid state relays and general relays is that there is no movable contacts in solid state relay (SSR). In general, solid state relays are quite similar to the mechanical relays that have movable contacts. ... SSR provide high-speed, high-frequency switching operations. 3. How fast is a solid state relay? The SSR output is activated immediately after applying control voltage. Consequently, this relay can turn on anywhere along the AC sinusoidal voltage curve. Response times can typically be as low as 1 ms. The SSR is particularly suitable in application where a fast response time is desired, such as solenoids or coils. 4. Do solid state relays get hot? All solid state relays develop heat as a result of a forward voltage drop through the junction of the output device. Beyond a point, heat will cause a lowering (or derating) of the load current that can be handled by the SSR. ... Loads greater than 4 Amps will require heat sinks. 5. What causes solid state relay failure? What are the main causes and solutions of the Solid-state Relays (SSR)'s failures? If an inrush current exceeds the rated making current of the SSR due to the high inrush current of loads such as motors and lamps, SSR output elements are damaged. Consider using an SSR with a higher capacity. 6. Can a solid state relay switch DC? Solid state relays can be designed to switch both AC or DC currents by using an SCR, TRIAC, or switching transistor output instead of the usual mechanical normally-open (NO) contacts. 7. How do you test a solid state relay with a multimeter? Using Multimeter:  1. Set the multimeter in continuity test mode. 2. Place the probes of the multimeter on the coil terminals. 3. If the multimeter beeps (or show any sign of continuity), the coil is electrically closed (good). 4. If the multimeter does not beep, the coil is open & damaged. The relay needs to be replaced. 8. How reliable are solid state relays? Solid-state relays are the preferred choice for system reliability because they have no moving parts or contacts. Over time, the plating on the contacts inside EMRs can erode. This erosion can cause the contacts to weld shut; therefore they no longer open/close properly, and the relay has to be replaced. 9. Is a solid state relay a transistor? Solid-State Relay: A sort of hybrid between a conventional relay and a transistor, these relays switch a load using an LED activated by the control circuitry. The LED activates a light-activated MOSFET that controls the load. 10. How do I know if my solid state relay is bad? Solid-state relays should be checked with an ohmmeter across the normally open (N.O.) terminals when control power is off. The relays should be open, switched to OL, and closed (0.2 , the internal resistance of the ohmmeter) when control power is applied. 11. How do I choose a solid state relay? When selecting a Solid State Relay, consider: Current rating, as a general rule consider using the relay at no more than 70% of its rated current. Electrical environment,. i(In harsh electrical environments, consider a relay with an line voltage rating above the application line voltage.) 12. Do solid state relays need a diode? 2 Answers. The control side of solid state relays is usually just a LED, sometimes two LEDs back to back, and sometimes with integrated resistor. ... If the relay is on the same board as whatever is driving it, then no inductive kickback diode is needed. It's no different than driving any other on-board LED. 13. Do solid state relays leak voltage? Solid State relays have leakage. If you want to repeatedly switch something on / off, use them. But when you want the SSR to be fully off, say after pressing an off switch, a mechanical relay should be across the load to take it off the SSR. ... The SSR control is attached to the atmega328 through a 200ohm resistor.

This article is a collection of 5 frequently asked questions about blower motor resistor. Catalog I. What is a Blower Motor Resistor? II. How Does the Blower Motor Resistor Work? III. How Do I Know If My Blower Motor Resistor is Bad or Broke? IV. How to Test a Blower Motor Resistor? V. Can I Fix the Blower Motor Resistor by Myself? FAQ I. What is a Blower Motor Resistor? The blower motor resistor is the blower motor component that regulates the speed. When you raise the thermostat on the air conditioner, the resistor sends a signal to the blower motor to speed up and blow more air. When you turn it down, the opposite happens. It is an electronic component that sends electronic pulses corresponding to the information you send through the adjustment dial. The electrical signal increases or decreases, which affects the overall motor speed of the fan. As far as electrical systems are concerned, they are simple, but as you might see, if something interrupts the flow of power, problems can occur.   Behind these vents in the dashboard, there is a blower motor that starts when you need heating or air conditioning. Usually, it is located in the dashboard on the other side of the steering wheel. You can't see it because it is inside the vehicle, but there it is.   A digital speed controller controls a variable speed motor. The controller typically receives a digital input from the speed switch or HVAC control head. The control head then sends a command to the motor controller to adjust the speed to the driver's requirements.   The motor controller rapidly pulses the ground circuit on and off to achieve the desired speed. So a half-speed driver request will result in the blower motor controller pulsing the ground connection off twice as often as when the fan is running at full speed.   The blower motor resistor or control module is often positioned within one of the ducts in the HVAC system, close to the blower motor, in most modern vehicles. This is done so that the resistor or control module can be cooled by passing air. A blower motor resistor was fitted on the firewall of some older vehicles, with access from under the hood.  II. How Does the Blower Motor Resistor Work? This video will give a detailed explanation of blower motor circuit to help you better understand how eactly it works. III. How Do I Know If My Blower Motor Resistor is Bad or Broke? There are a few indications that your car's blower motor resistor has failed. Because the symptoms may overlap with difficulties in other systems in your vehicle, you may require the assistance of a specialist to help you diagnose them. These are some of the most typical warning signs. (1)  No air. As simple as it may sound, one of the most noticeable indicators to look for is a lack of air moving through the vents when trying to get the heater or air conditioner to function. If nothing comes out when you turn the knob or press the button and it's intended to start blowing air, it's a good clue that the blower motor resistor has failed. This can be a sign of a variety of different issues, so don't take it as a given if this is the only signal you're receiving.   (2)  High speeds only. As previously stated, a blower motor resistor is not required in two situations. When the fan is totally turned off or when it is running at high power. Because the current does not need to be modulated at high power, it bypasses the resistance. So, if you discover that your heat and air conditioning can only switch from being completely off to being on at high power, it's almost certain that you have a broken blower motor resistor.   (3)  Low speeds only. When your fan only works at low speed, this may be a signal of poor blower motor resistance as well. However, when there is a wiring problem between the blower motor resistor and the blower motor itself, it may only work at low speeds.   (4)  The fan will not turn off. If you can't turn off the fan no matter what you do, and no matter how you try to go up, down, or turn off the fan, the fan is constantly running, which means that the blower motor resistor cannot properly regulate the current.   (5)  The blower motor works under certain settings, but does not work under other settings. The blower motor should have a series of settings, from low to high, which can be set in a variety of intermediate ranges. If you find that some of these intermediate settings are working and some of them do nothing at all, it probably means that there is a problem with the switch, and how the switch sends a signal about your settings to the blower motor resistor blower motor.   (6)  Smoking vents. This is an unusual signal of a faulty blower motor resistor, though it is not unheard of. If there is a short around the blower motor resistor and wires begin to melt, the fan may spew smoke from those melting wires back into your car's cabin.   A solid rule of thumb is that if smoke starts flowing in via your car's vents, you should pull over immediately and figure out what's wrong. If it isn't the blower motor resistor, it could be something more serious, and you should get it checked out as soon as possible.   (7)  Burning Smell. Similarly to the smoking vent issue, it is not always as dangerous as actual smoke billowing into the car's cabin, but you will detect the distinct burning smell that indicates that some metal or plastic is overheated somewhere in the vehicle. This is frequently associated with one of the other signals we've already mentioned above. IV. How to Test a Blower Motor Resistor? Blower motor resistor test V. Can I Fix the Blower Motor Resistor by Myself? Whether you can repair the blower motor resistor yourself obviously depends on how much you know about blower motor resistors and general car maintenance. If you are reading a guide on blower motor resistance and its functions, you may not be familiar with them. Therefore, we recommend that you do not try to fix this problem yourself, as this is not a beginner-level fix.   This is not to say that you cannot replace the blower motor resistance yourself, but it will be a complicated task. But we provide you with some basic methods to diagnose and repair some simple blower motor problems, for reference only. For specific steps, please consult professionals or check related videos on youtube.   (1) The blower only works in high speed. This is a sure sign of a bad blower motor resistor, not a faulty speed switch. Change the resistor.   (2) The blower only works in low speed. Check for a blown fuse or a faulty high-speed relay. Replace the high-speed relay with a relay of the same part number. Check the fuse for the high speed relay's control side as well. Verify that the high speed relay's ground side is good.   (3) Repeated failures of the blower motor resistor Check for full airflow at the vents. If airflow appears to be restricted or lower than typical, a blocked cabin air filter is to blame. Examine the cabin air filter. If everything is ok, look for debris on the evaporator or heater. When the airflow is reduced, the blower motor resistor overheats and fails. Reduced airflow forces the blower motor to work harder and draw more current, which might result in repeated blower motor resistor failures. FAQ 1. What does a resistor do on a blower motor? Blower resistors are resistors which are used to control the fan speed of automotive blowers. The fan speed can be changed either by switching the blower resistor resistance mechanically, using a rotating lever, or electronically by the air conditioning system. 2. Can I bypass blower resistor? Blower resistors are resistors which are used to control the fan speed of automotive blowers. The fan speed can be changed either by switching the blower resistor resistance mechanically, using a rotating lever, or electronically by the air conditioning system. 3. What can cause a blower motor to stop working? In a situation where the motor doesn't work on any speed, the most likely causes are: a blown power supply fuse, a bad motor ground connection, bad motor speed control module or a failed motor. On all systems, a failed blower motor is least likely. ... Start by checking the blower fuse and HVAC controller fuse. 4. How do you test a blower motor resistor with a multimeter? Place one lead of the Ohmmeter on terminal 1 of the resistor. Place the other lead on terminal 2 and check against specifications. If this circuit is open, showing infinity on the Ohmmeter, the blower resistor must be replaced. Move the lead from terminal 2 to terminal 3 and check this reading against specifications. 5. Is the blower motor resistor supposed to get hot? Yes that resistor will get very hot. Most people don`t know this but it is faster to defrost the windshield on low or medium fan speed due to that resistor putting off heat. Also that resistor needs to be cooled off with the air flow or it will burn up . 6. What is the function of a blower motor resistor? A blower motor resistor is an adjustable resistor. This electrical component is used to control the air conditioning system of a vehicle. It is the part that controls the fan speed of the fan motor according to settings that can be changed by turning the knob to the left or right, thereby increasing or decreasing the resistance of the electric current flowing to the rotating fan motor connected to the fan. 7. Where is the blower motor resister? A blower motor resistor, typically located beneath the passenger side dashboard, contains three resistors, or sets of terminals designed to generate voltage in proportion to electrical current. 8. How do you replace a blower motor resistor? Safety Tip: Always wear safety glasses when working on your motor. Wear other personal protective equipment (PPE) when necessary, for example latex gloves or closed toe shoes. 1.Remove the negative battery terminal.2.Locate the blower motor resistor on the passenger side under the dash board. It is mounted to the the blower housing near the blower motor.3.Disconnect the electrical connector to the blower motor resistor.4.Remove the screws or bolts to the blower motor resistor and remove the resistor.5.Installation is the reverse of the removal. 9. Can you test a blower motor resistor? Yes. Set your multimeter to Diod or continuity and place leads on either side of the resistor. If no tone and infinite resistance it is bad. If tone but no resistance it is bad. If you have continuity to ground, something has shorted to ground look for heat damage. If you have tone and resistance it is good.  10. Why does a blower motor resistor keep going out? If you are constantly blowing that part. You ether have the motor pulling to much amps. If it is home unit it could also be a inline control board cap.