SU1283925A1 - Device for controlling rotational speed of induction electric motor - Google Patents

Abstract

The invention relates to electrical engineering and can be used in drives of lifting machines and passenger elevators. The aim of the invention is to improve the smooth control of the rotation frequency. This goal is achieved by introducing an asynchronous motor into the device for controlling the rotational frequency of the number of motor phases 30,31,32, each of which is composed of successively connected resistors and anti-parallel connected thyristors. The device is connected in series with amplifier 14, voltage-frequency converter 15, and a three-phase ring counter 16. The input of amplifier 14 is connected to the output of comparison element 6, and the output of counter 16 is connected to one of the inputs of each AND 17-22 logic element. The second inputs of the elements 17-22 are connected to the inverting output of the RS flip-flop 12. The outputs of the elements 17-22 are connected via power amplifiers 23-28

Description

control circuits of entered thyristors. The introduction of these blocks and elements reduces the current-free pause time when the electric motor is operating in quasi-frequency mode and provides a step change in voltage

925

stator winding with quasi-frequency control. This reduces the change in magnetic flux at each switching of the electric motor in quasi-frequency mode. As a result, the smoothness of the adjustment is increased. 2 Il.

one

The invention relates to electrical engineering and can be used in automated electric drive systems, in particular in the drives of lifting machines and passenger lifts.

The purpose of the invention is povshhenie. smooth speed control

Fig. 1 is a circuit diagram of a device for controlling the speed of an asynchronous motor; 2 shows timing diagrams for his work.

A device for controlling the rotation frequency of the asynchronous motor 1 contains a thyristor switch 2 connected to the phases of the induction motor 1. The thyristor switch 2 is made in the form of counter-connected thyristors. The device also contains a phase control unit 3 and a quasi-frequency control unit 4, oppositely connected by the thyristors of the switch 2, a rotation frequency setting unit 5, a reference element 6, two potentiometers 7 and 8 settings, two operating controllers, a control pulse strength 11 , KZ trigger 12, a rotational speed sensor 13 fixed on the shaft of the induction motor 1, the rotation speed setting unit 5 is connected to the first input of the comparison element 6, the second input is connected to the rotational speed sensor 13, and the output of the comparison element 6 is connected to the first inputs of the blocks of the phase and quasi-frequency control 3 and 4 by opposite-connected thyristors of the switch 2, the second inputs of which are connected respectively to the forward and the invert

j

ABOUT

5 0 5 About

five

0

short-circuit trigger outputs, and the outputs of blocks 3 and 4 are connected to the amplifier 11 of the control power of the switch torster's strings 2, the inputs of operational amplifiers 9 and TO, the first inputs of which are connected to the second input of the control unit, and the second inputs accordingly with the potential. meters of settings 7 and 8. In addition, the device contains a series-connected amplifier 10, a voltage-frequency converter

15, a three-phase loopbacks 16j, the output of which is connected to one input of each of the six logic gates AND 17-22, the outputs of which are respectively connected to the inputs of six power amplifiers 23-28; and the other inputs of each of the six logic elements AND 17-22 are connected to the usher output of the RS flip-flop 12 and the outputs of each of the six actuators 23-28 are connected to the corresponding control electrodes of the additional anti-parallel-connected thyristors 29 connected in each phase in series with the resistors 30 ,, 31 and 32 and parallel. thyristor switch 2, figure 2 shows the control spacing sequences 33 and 34 generated by the quasi frequency control unit 4 (e.g., for opposite, parallel to the connected thyristor thyristor 2 in phase A), power supply voltage signals 35. BUT; sequences of control pulses 36, 37 at the output of a three-phase ring counter

16, supplied, for example, to additional anti-parallel-connected thyristors 29 in phase A: signals

3- fO

or block 4 of quasi-frequency control of anti-parallel thyristors connected to thyristor switch 2. Thus, a part of the entire frequency control range of the asynchronous motor 1 is provided with a quasi-frequency control, and a part of the phase control.

At the same time, the error signal from the output of the comparison element 6 is fed through the amplifier 14 to the voltage-to-frequency converter 15, the output pulse sequence of which has a frequency equal to the voltage of the thyristor switch 2 and the thyristor switch 2 in the stator winding additional counter-connected thyristors 29 (all signals are shown, for example, for dividing the mains frequency by 6).

A device for controlling the rotational speed of an asynchronous electric motor works as follows.

From the rotational speed setting unit 5, an input signal proportional to the predetermined rotational frequency f5 is obtained to modulate the block 4 of the quasi-frequency asynchronous motor 1, which is controlled by a three-phase motor, and is then compared to the rotational speed sensor 13 on the comparison element 6. The error signal from the output of element 6 of comparison 20 is fed to one of the inputs of blocks 3 and 4 of phase and quasi-frequency control of anti-parallel connected thyristors of the thyristor switch 2, while the other 25 are fed from the output of a three-phase ring; the corresponding counter signals from the RS flip-flop 12. Depending on the control signal from the output of the RS flip-flop 12, either the phase block 3 or the quasi-frequency control block 4 starts operating, respectively a sequence of control pulses that, through amplifier 11, arrive at the control electrodes of oppositely connected thyristors of the thyristor switch 2. For example, when the block 4 of the quasi control frequencies is operating, these pulses look like 33.34 serially connected thyristors of control pulse pulses (for example, on-switch 2, operating in 36.37 signals), which are via phase A). The source voltage of the power supply amplifiers 23-28 for this phase is shown in diag. On the control electrodes of frame 35. From the sensor 13, the frequency of rotation-45 Additional anti-parallel or parallel signal proportional to the frequency of the switched thyristors 29. Almost asynchronous rotation the electric motor-amplifier 14, the converter of the tel 1, is fed to the input of the operation-frequency 15, the three-phase ring amplifiers 9 and 10 and the counter 16 is compared, the logic elements in size with different voltages are 50 17-22, If the power of 23–28 is set at the corresponding settings, one more channel of quasi-frequency meters 7 and 8 will be lazy formed; At the same time, at the output of the one-control, but the control channel of the preamplifiers 9 and 10 (depending on the counter-parallel width From the magnitude of the voltage set by the included thyristors 29 forming the potentiometers 7 and 8), the control pulses are generated, unregulated, „„ „„ „„ „„ „„, 1 ..- in phase and fed to the control

the electrodes of the corresponding thyristors 29 at the beginning of each work for them

A ring counter 16, which is a ring scaling circuit that forms a three-phase pulse system, with a shift by 120 al. and offset one relative to the other by 180 degrees.

Thus, at the inputs of each of the six logical elements AND 17–22, the sequence of pulses (for example, for additional counter-parallelly connected thyristors 29 in phase 30 A) at the output of the logical elements 17,18, these signals have the form 36, 37 (FIG. 2) with a frequency equal to the modulating frequency of the quasi-frequency control unit 4, and a control signal from the inverting output of the RS flip-flop 12. If there is a signal 1 at this output of the RS flip-flop 12 at the outputs of each of the six logic elements 17 -22 occur 35

either logic signal 1 or O. These signals provide switching of RS flip-flop 12 and, accordingly, operation of either block 3 of the phase half-cycle of the supply voltage. With

fO

or block 4 of quasi-frequency control of anti-parallel thyristors connected to thyristor switch 2. Thus, a part of the entire frequency control range of the asynchronous motor 1 is provided with a quasi-frequency control, and a part of the phase control.

At the same time, the error signal from the output of the comparison element 6 is fed through the amplifier 14 to the voltage-frequency converter 15, whose output pulse sequence with a frequency equal to one hour

f5 modulation unit 4 of the quasi frequency control, enters the three-phase 20 25 enters from the output of the three-phase ring counter 16, the corresponding 40 sequences of control pulses (for example, 36.37 signals), which through the corresponding power amplifiers 23-28 are fed to control electrodes 45 Additional additional anti-parallel-connected thyristors 29. Practically amplifier 14, voltage-frequency converter 15, three-phase ring counter 16, logic elements 50 17-22, power amplifiers 23-28 ob- another kvazichastotnogo form a control channel, control channel but possible additional co-parallel connected thyristors 29 generates a "control pulses with fixed phase and supplied to the control

modulation of the block 4 of the quasi-frequency control, supplied to the three-phase-comes from the output of the three-phase ring counter 16 corresponding to the frequency of the sequence of control pulses (for example, signals 36,37), which, through the corresponding power amplifiers 23 -28 are fed to control electrodes of Additional anti-parallel-connected thyristors 29. Practically amplifier 14, voltage-frequency converter 15, three-phase ring counter 16, logic elements 17-22, power amplifiers 23-28 t is another quasi-frequency control channel, but the control channel by additional anti-parallel pin-connected thyristors 29 generates control pulses unregulated about the phase and fed to the control

A ring counter 16, which is a ring scaling circuit that forms a three-phase pulse system, with a shift by 120 al. and offset one relative to the other by 180 degrees.

Thus, the inputs of each of the six logic elements AND 17-22 f5 modulation moduli of the quasi-frequency control unit 4, is fed to a three-phase-20 25 output from the output of a three-phase ring counter 16 corresponding to 40 control frequency pulses (for example, signals 36,37), which through the corresponding power amplifiers 23-28 are fed to control electrodes 45 Additional anti-parallel connected thyristors 29. Practically amplifier 14, voltage-frequency converter 15, three-phase An annular counter 16, logic elements 50 17-22, power amplifiers 23-28 form another channel of quasi-frequency control, but the control channel with additional anti-parallel-w connected thyristors 29 forms control pulses that are out of phase and are fed on managers

The pulse length (for example, for additional anti-parallel thyristors 29 in phase 30 A) at the output of logic gates AND 17.18, these signals look like 36.37 (FIG. 2) control with a frequency equal to the modulating frequency of block 4 a quasi-frequency control, and a control signal from the inverting output of the RS flip-flop 12. If there is a signal 1, this output of the RS flip-flop 12 on the outputs of each of the six logic gates And 17-22

 half period supply voltage. With

When forming the resulting half-cycle of the power supply in the quasi-frequency mode of operation of the asynchronous motor 1 for each phase at the beginning of the working half-period, one of the thyristors 29 comes into operation (for example, for phase A at point B in diagram 38), and then at P-y the control impulse is blunt from the quasi-frequency control unit 4 and the corresponding thyristor of the thyristor switch 2 (for the same phase A, at point D in diagram 38). So far, in operation one of the thyristors 29, the voltage on the asynchronous motor 1 is determined by the value of the corresponding one of the resistors 30 5.31 and 32. When the corresponding thyristor of the thyristor switch 2 comes to work, the corresponding thyristor from the thyristors 29, (( Point G in diagram 38) applies a voltage locking the latter, and the voltage on the stator winding of the asynchronous motor 1 increases stepwise (diagram 38).

Similar operation of the thyristors 29 and thyristors of the thyristor switch 2 takes place in other phases in the quasi-frequency mode.

Thus, the use of the invention. shadow allows to reduce the current-free pause time when an asynchronous electric motor is operating in quasi-frequency mode and to provide a step change in voltage: generated on the stator winding during each half-period of the resulting period with quasi-frequency control.

This reduces the resulting change in the magnetic flux of the motor at each switching in the quasi-frequency mode of operation and, accordingly, the transitional alternating components of the torque of the electric motor. As a result of smooth adjustment, dynamic overloads are reduced, which increase wear and shorten the service life of the equipment of both the drive mechanism and the device itself, which causes its reliability.

Claims (1)

Invention Formula An apparatus for controlling the rotational speed of the induction motor, comprising: a thyristor switch operable to connect the stator windings of the asynchronous motor with istochvsh om pitaVIYa which is arranged in vi, n; e-parallel connected thyristors, the phase and kvazichastotnogo control units thyristors kommutatoraz connected with the control chain thyristors through an amplifier, the frequency setting unit p whose output is connected to the first input of the reference element, the second input of which is connected to the output of the frequency sensor rotation of the rotor of the asynchronous motor and with the first inputs of two operational amplifiers, the vypud comparing element is connected to the first inputs of the phase and quasi frequency controlling the thyristors of the kh.-gututor, the second inputs of which are connected respectively to the prmg and the inverting output of the short-circuit flip-flop, the inputs of which are connected to the video codes of the operadion amplifiers, and the second inputs of the operational amplifiers of the switches are connected to the corresponding device potentiometers differing from 01st , with the fact that, in order to increase the smoothness of the regulation of the rotation frequency, j with it entered into a new phase of the motor. chains of series-connected resistors and additional counter, 1 tara. successively connected accelerators, an input connected to the output of a reference element, a voltage-frequency converter and a three-phase ring face pulse counter, six logical And elements and six power amplifiers, with chains of series-connected resistors and anti-parallel connected thyristors of the switch, the outputs of the ring counter are connected to the first inputs of the AND elements, the second inputs of which are connected to the RS inverting output, and the outputs of the AND elements power amplifiers are connected to control electrodes of additional anti-parallel thyristors. 53 P 3 3536 D.JBJ J 38 .Jv .... 5 / l7 .2 Tl Jl