单相交流调压电路设计(DesignofsinglephaseACvoltageregulatorcircuit)

1、单相交流调压电路设计( Design of single phase AC voltage regulator circuit )DOCdocuments mayexperience poor browsing on the WAPside. It is recommendedthat you first select TXT, or download the source file to the local view.Design of single phase AC voltage regulating circuit, design of single-phase AC voltage

2、regulating circuit, AC voltage regulating circuit1 design objectives and requirements analysisThe design of a single-phase AC voltage regulator circuit requires a trigger angle of 45 degrees. The back EMF load is E=40 volts and the input is AC U2=210 volts. There are no LB and LB two of.L is large e

3、nough, C analysis of large enough requirements: 1. single-phase AC voltage design, main circuit principle; 2. trigger circuit design, analysis of sequence and phase of each switch trigger; 3. protection circuit, overcurrent protection, overvoltage protection principle and setting analysis; the calcu

4、lation of 4. parameters (including the trigger angle, average output voltage, average output current, output active power calculation, output waveform analysis, determine the rated parameters of the device can add their own analysis parameters); from the above design requirements of the system can b

5、e divided into four parts: the AC voltage main circuit, trigger circuit design protection circuit design and related calculation and waveform analysis part. Here are a detailed introduction.2 the design selection adopts two common thyristor reverse parallel design single-phase AC voltage regulating

6、circuit 3 single-phase AC voltage regulation main circuit design and analysisAC voltage regulation means that the two thyristors are connected in series in an AC circuit after they are connected in parallel. In each half cycle, the effective value of the output voltage can be adjusted conveniently b

7、y controlling the phase of the thyristor.ACvoltage regulating circuit is widelyused in light control and asynchronous motor soft start, also used in asynchronous motor speed regulation. In addition, in the high voltage, small current or low voltage, high current power supply, AC voltage regulation c

8、ircuit is often used to adjust the primary voltage of the transformer. The course design is mainly to study the design of single-phase ACvoltage regulation circuit. Because the working condition of ACvoltage regulating circuit is closely related to the nature of the load, the anti EMF and resistance

9、 load are discussed below.OneFigure 1 and Figure 2 are respectively the back EMF, the resistance load, the single-phase AC voltage regulation circuit and the waveform. The thyristors VT1 and VT2 in the picture can also be replaced by a bidirectional thyristor. The output voltage can be adjusted by c

10、ontrolling the phase shift control angle of the VT1 and VT2 in the positive half and half half cycles of the AC power U2.Fig. 1 single phase ACvoltage regulation circuit with back EMFresistance loadFig. 2 waveform of input and output voltage and currentThe positive and negative half cycle alpha star

11、t times (alpha =0) are voltage zero crossing times. At t = Alpha Omega, applying trigger pulse to VT1, whenVT1 positive bias is turned on, the load voltage waveform and power supply voltage waveform in the same; omega = Pi T, power supply voltage zero, due to a resistive load, current is zero, VT1 t

12、urned off. stayWhen Omega t = Pi + alpha, a trigger pulse is applied to the VT2, and the waveform of the load voltage is shifted when the VT2 is biased forwardThe sameas the supply voltage waveform; at Omegat = 2 pi, the power supply voltage is zero, and the VT2 is turned off naturally. Whenthe powe

13、r supply voltage reverse zero, because of the back EMF load prevents current changes, so the current can not be immediately to zero, the thyristor conduction angle size, not only related to the control angle, but also related with the load impedance angle. The initial control points of gate gates of

14、 two thyristors are set at the starting point of each half of the supply voltage respectively. When the steady-state is equal to the positive and negative half weeks, the load voltage waveform is part of the supply voltage waveform, and the waveform of the load current (the supply current) is simila

15、r to that of the load voltage.4 trigger circuit designTwoThe thyristor trigger circuit is used to generate gate trigger pulses that meet the requirements and to ensure that the thyristor is switched off to conduction at the desired time. Broadly speaking, thyristor trigger circuit often includes a p

16、hase control circuit of the trigger time of the control, but here refers to pulse amplification and output. The thyristor trigger circuit shall meet the following requirements: 1) the width of pulse should ensure reliable thyristor conduction of the converter, back EMF load should be used in pulse w

17、idth or pulse trigger; 2) trigger sufficient amplitude, on cold outdoor occasions, amplitude of pulse current should be increased to 3-5 times the maximum trigger current, pulse steepness may increase, the general should be 1-2A/us; 3) provided the trigger pulse voltage, current and power should not

18、 exceed the thyristor gate and the gate of the quota, the volt ampere characteristics of reliable trigger area; 4) electrical isolation of anti-jamming, stability and temperature the main circuit and the. According to the above requirements analysis, the KC05 phase shift trigger is used to design th

19、e trigger circuit.KCO5silicon controlled phase shift trigger is suitable for AC phase control of bidirectional thyristor or two reverse parallel thyristor. The KC05pin diagram is shown in figure 3:Figure 3 KC05 pin diagramKC05trigger chip has the advantages of good sawtooth waveform, wide range of p

20、hase shift, simple control mode, easycentralized control, loss of protection, high output current and so on. It is an ideal circuit for AC dimming and voltage regulation. The KC05circuit is also suitable for phase control of semi controlled or fully controlled bridge lines.Synchronous voltage from 1

21、5, 16 feet KC05 input, TP1 can be observed in the sawtooth wave, RP1potentiometer to adjust the slope of the sawtooth, Rp2 potentiometer to adjust the phase angle, the trigger pulses from the pulse transformer output of ninth feet. Adjust potentiometer RP1, observe sawtooth slope change, adjust RP2,

22、 can observe the output pulse phase shift range, how to change the single-phase AC voltage trigger circuit diagram, as shown in figure 4:ThreeFig. 4 Schematic diagram of single phase ACvoltage regulating trigger circuit5 protection circuit designIn the power electronic circuit, besides the choice of

23、 the parameters of the power electronic device and the design of the drive circuit, proper overvoltage, overcurrent, du/dt protection and di/dt protection are also necessary. 1 over voltage generation and over-voltage protection, the possible overvoltage in power electronic devices is divided into t

24、wo categories: external factor, over voltage and internal overvoltage. Be mainly from overvoltage reasons, external lightning in the system operation process includes: 1) operating voltage:the overvoltage caused by separate switch,switching operation, fast switch off DC electromagneticprocess often

25、caused by overvoltage in operation.Four2) lightning overvoltage: overvoltage caused by lightning stroke. The switching process, Internal Overvoltage mainly from internal devices of power electronic device includes: 1) commutation overvoltage due to thyristor full controlled devices or anti parallel

26、after not immediately restore blocking diode in phase change after the end of the reverse current flow through the larger, so that the residual carrier recovery, when the restore the blocking capability, reverse current decreases sharply, so the current mutation due to inductance in the two ends of

27、the thyristor full controlled devices or between anode and cathode with diode anti parallel overvoltage. 2) turn off overvoltage: the full controlled device works at higher frequencies. Whenthe device is turned off, the voltage across the device is induced by the inductance of the line inductance du

28、e to the rapid decrease of the forward current. According to the different parts of the overvoltage protection circuit overvoltage protection circuit is generated, adding different, when reaching certain voltage, automatically open circuit protection, overvoltage protection circuit formed by the pat

29、hway of electromagnetic energy consumption, overvoltage storage, so that the energy is not added to the main switching device Overvoltage on protection of power electronic devices. In order to achieve the protection effect, the resistance capacitance protection circuit can be used. Whenthe capacitor

30、 is connected in the loop, whenthe voltage spike voltage occurs in the circuit, the voltage at both ends of the capacitor can not be mutated, and the overvoltage in the circuit can beeffectively suppressed. A resistor connected in series with the capacitor can consume part of the overvoltage energy,

31、 while suppressing the inductance and capacitance in the circuit to oscillate. The overvoltage protection circuit is shown in figure 5.Figure 5 RC resistance capacitance overvoltage protection circuit2 over current protection. Excessive current mayoccur whenthe power electronics circuit is not opera

32、ting properly or when a fault occurs. When the device breakdown or short circuit, trigger circuit or control circuit failure, overload, short circuit, reversible DC transmission system produces circulation or inverter failure, and AC power supply voltage is too high or too low, the lack of equal, ca

33、n cause the flow.Since the current overload capacity of power electronic devices is relatively poor, it is necessary to carry out over-current protection for converters. Fast fuse is the most effective and widely used over-current protection method in power electronic devices.FiveFig. 6 overcurrent

34、protection circuitThe overcurrent protection circuit as shown in Figure 6, the AC side connected fast fuse tube protection short circuit element short circuit and DC side of thyristor, but normal operation, fast fuse current rating is greater than the current of the thyristor protection effect of th

35、is poor quota, thecomponents of the short circuit fault. The DC side quick fuse only protects the short circuit from the load and has no protective effect on the component. Only thyristor directly connected to a fast fuse is the best protection for components because they flow through the samecurren

36、t and are widely used. As the first electronic circuit protection fuse protection only as part of the section of short circuit, DCfast circuit breaker setting protection in electronic circuit, overcurrent relay operating in overload.Parameter setting and calculation of 6 phase AC voltage regulation

37、circuit1) parameter setting of single-phase ACvoltage regulator: the trigger angle is 45 degrees, the back EMF load is E=40 volts, and the input is AC U2=210volts. There are two cases of LB and no LB. The L is large enough and the C is large enough. 2) single-phase ACvoltage regulator converter circ

38、uit analysis: in the single-phase AC voltage regulator circuit diagram, thyristor VT1 and VT2 can also be replaced by a bidirectional thyristor. The output voltage can be adjusted by controlling the turn-on angle of VT1 and VT2 in the positive half and negative half cycles of the ACpower U2. The sta

39、rting time (=0) of positive and negative half cycles is zero crossing time. In the steady state, it should be equal to the positive and negative half weeks. It can be seen that the load voltage waveform is part of the voltage waveform of the power supply, and the waveform of the load current is the

40、same as the load voltage. 3) output average voltage, current and output active power calculation, first set resistance value R = 100, divided into LB and no LB two cases analysis. When there is no leakagesense LB, when the opening angle is set as alpha, the effective value of the load voltage is U0,

41、 the effective current value of the load current is I0, the RMS current of the thyristor current is IVT, and the power factor of the circuit is lambda. According to the formula, the following results are obtained:= U01 PI + alpha formula (2U 2 sin T 2 D (omega) = Alpha PI Omega T) =201.87VI0 = U0, =

42、2.02A, R(1)(2)SixIVT=1 PI + alpha 2U 2 sin WT (2) d (WT) = 2 pi alpha 1.43A formula RLambda = P, U0I0, =0.961 = S, U 2, I0(3)When the leakage inductance is considered, there is alwaysleakage in the transformer windings LB. Because the inductance is a hindrance to the current change, the inductance c

43、urrent can not be mutated, so the commutation process can not be completed instantaneously, but will last for some time. The influence of leakage inductance LB on the related parameters in the commutation process is analyzed below. In the commutation process, the instantaneous value of the output vo

44、ltage isUd = Ua + LBDik, Dik, Ua + Ub = Ub = LB = DT DT 2(5)It can be seen that in commutation process, the rectifier voltage U D is the average value of the two thyristors with the corresponding two phase voltages simultaneously. Comparedwith the transformer leakage inductance, the U D is reduced b

45、y one piece each time, which leads to the average reduction of U D, and reduces the number of U D. This is called the phase change voltage drop. (6)Ud = X, B, IdPIWhere XB=w LB. XB converts the leakage inductance of the LB transformer to the two term leakage reactance. At the sametime, we can obtain

46、 the change of overlap angle gamma, which can be obtained by the lower form.Cos alpha cos (alpha + lambda) =IdXB 2U 2(7)The change law of the change phase overlap angle with other parameters is as follows: whenId is bigger, the gammais bigger; when XBis bigger, the gammais bigger; whenalpha =90 degr

47、ees, the alpha is smaller, then the gamma is bigger. The influence of leakage inductance on the circuit is analyzed as follows: (1) the phase change overlap angle and the average output voltage of rectifier Ud are decreased. (2) the working state of the rectifier circuit is increased (3) the di/dt o

48、f the thyristor is reduced, which is beneficial to the safe opening of the thyristor.Sometimes artificialinput line reactors areused to suppress the thyristor di/d t. (4) whenthe commutation occurs, the thyristor voltage gap occurs, resulting in a positive du/dt, which may cause the thyristor to mis

49、lead. Therefore, an absorption circuit must be added.Seven(5) commutation causes the voltage of the grid to become a source of interference.Harmonic analysis of 7 single-phase AC voltage regulating circuitThe load voltage and load current of single phase AC voltage regulating circuit are not sinusoi

50、dal wave, and contain a large amount of harmonic. Taking the resistive load as an example, the harmonic analysis of the load voltage U0 is made. Since the positive and negative half wave of the wave is symmetrical, there is no DC component or even harmonic.8 design summary and experienceThe power el

51、ectronic technology curriculum design, so that we have the opportunity to learn the theoretical knowledge used in the classroom in practice. And through the comprehensive utilization of knowledge, the necessary analysis, comparison. And further verify the theoretical knowledge. At the sametime, the

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