SU1249683A1 - Device for controlling induction electric motor - Google Patents

Abstract

This invention relates to electric drives. The aim of the invention is to increase the efficiency and reliability of the control device of an induction motor. In the mode in which the thyristor 4 shunts the resistor 3, it is not switched on by the thyristor 5. A threshold element 12 and a delay element 22 are connected to the commutation capacitor through the command device 11. When a certain voltage is reached at the capacitor 6, the first single-transistor transistor 13 turns on, and the secondary winding of the transformer 14 with S (L with bppplllll 4: o O) 00

Description

a pulse is formed, the thyristor 5 is opened, and the thyristor 4 is closed. Through the thyristor 5, the recharging of the switching capacitor 6 to the voltage of the slider 2 occurs. Through the resistor 26 the conf is started to charge.

The invention relates to electrical engineering and is intended for adjustable asynchronous motors with a phase-rotor, in the circuit of which a pulse converter is included.

The purpose of the invention is to increase efficiency and reliability.

FIG. 1 is a circuit diagram of the device, as shown in FIG. 2. - block diagram of the thyristor control unit.

The device for controlling asynchronous motor 1 contains a three-phase bridge rectifier 2, a power resistor 3, a main 4 and switching 5 thyristors, a switching capacitor 6, a recharge throttle 7, a first diode 8, a sensor 9 of a stator current of an asynchronous electric motor,. 1, the control unit 10 of the main 4 and auxiliary 5 thyristors, a command device .11, the output of which is connected to one input of the control unit 10 of the main 4 and switching 5 thyristors, the other input of which is connected to the output of current sensor 9. The outputs of the control unit 10 of the main 4 and switching 5 thyristors are connected to the control transitions of the corresponding thyristors 4 and 5. The connection point of the cathodes of the valves of the three-phase bridge terminal 2 is connected to one output of the power resistor 3, to the anode of the main thyristor and through the switching capacitor 6 to the anode the switching thyristor 5, with one output of the recharged throttle 7. The connection point of the anodes of the valves of the three-phase bridge terminal 2 is connected to another output of the power resistor 3, with the cathodes of the main 4 and mutating 5 thyristors and the anode of the first diode 8, the cathode of which is connected with the other terminal of the overcharge-stand choke 7. Entrance treh1249683

A capacitor 25. As a result, the uncoupled transistor 23 is turned on, and a pulse is formed on the secondary side of the transformer 24, the thyristor 4 is opened, and the capacitor 6 is recharged. The process then repeats. 2 or

the phase bridge of the miter 2 is connected to the rotor circuit of the electric motor 1. The device also contains a threshold element 12 composed

from the first single-junction transistor 13, the first transformer 14, the first, 15 and second 16 resistors, the second 17 and third 18 diodes, the variable resistor 19, the zener diode

20 and the first capacitor 21. The cathode of the Zener diode is connected to one output of the first resistor 15, to the gate of the first single junction transistor 13 and to one output of the first capacitor 21-, the other output of which

connected to the anode of the Zener diode 20, with ONE; the primary output winding of the first transformer 14 and one output variable resistor 19, the other output of which is connected to another output of the first resistor 15 and the cathode of the second diode 17. The anode of the diode 17 is connected to the anode of the switching thyristor 5, the anode of the Zener diode 20 to the anode of the main thyristor 4 The middle terminal of the variable resistor 19 is connected to the drain of the first single junction transistor 13, the rod of which is connected to a different terminal of the primary winding of the first transformer 13, the secondary winding of which through the third diode 18 and the second p Resistor 16 - connected to the control transition of the switching thyristor 5.

35

Delay element 22 composed

from the second single junction transistor 23, the second transformer .24, the second capacitor 25, the third 26 fourth 27 and fifth of 28 resistors, the fourth 29 and fifth of 30 diodes. One second of the second capacitor 25 is connected to the output of the third resistor 26 and to the gate of the second single junction transistor 23, the drain

which is connected to the output resisto3

pa 27, a source - to the output of the primary winding of the second transformer 24, another output of which is connected to another output of capacitor 25, with the anode of the fourth diode 29 and connected to the anode of the main thyristor 4. The other outputs of the third 26 and fourth 27 resistors are combined and connected to the cathode the fourth diode 29, the secondary winding of the second transformer 24 is connected to the control transition of the main thyristor 4.

The control unit 10 comprises a start generator 31, a switch thyristor control generator 32, a main thyristor control generator 33, a first 34 and a second 35 magnetic amplifiers. The outputs of the first 34 and second 35 magnetic amplifiers are connected respectively to generators 32 and 33, the outputs of which are connected to the control transitions of the corresponding thyristors. The output of the start generator 31 is connected to the starting input of the generator 32 controlling switching thyristor 5, the output of which is connected to the starting input of generator 33 controlling the main thyristor 4. The output of the latter is connected to the starting switch of the generator 32 controlling switching thyristor 5 and to the controlling input of the generator 31 launch.

The device works as follows.

In a mode in which the main thyristor 4 completely shunts the power resistor 3 and does not switch on by the switching thyrio 5, the switching capacitor 6 is discharged through the resistor 3, auxiliary circuit elements and leakage resistance. At this position, the threshold element 12 and the delay element 22 are connected to the commutator capacitor 6 (fifth position) through the command device 11 (fifth position). The plus capacitor 6 capacitor 6 through the second diode 17 enters the input of the element 12. When the voltage on the capacitor 6 reaches a certain minimum value that is still sufficient for switching, the first single junction transistor 13 is turned on, and the secondary winding of the first transformer 14 is formed the impulse that nocTjmaeT to the control electrode of the switching thyristor 5. As a result, the thyristor 5 is turned off, and

49683.

the main thyristor 4 is closed. Through the open thyristor 5, the commutation capacitor 6 is recharged to a voltage equal to the voltage of the three-phase bridge terminal 2. The positively charged plate of the capacitor 6 is now connected to the anode of the main thyristor 4. Plus the capacitor 6 through the fourth diode

10 29 falls on the element 22 of the delay. Through the third resistor 26, the capacitor 25 begins to charge, and when a certain voltage is reached on it, the second one is turned on.

15 the transistor 23, a pulse is applied to the secondary winding of the second transformer 24, which is supplied to the main thyristor 4. The latter is opened, and the switching capacitor is switched

20 6 is recharged through the thyristor 4, the first diode 8 and the recharged choke 7 to the initial voltage -. After some time, if the voltage on the capacitor 6 decreases, the process repeats.

The voltage at which the threshold element 12 is triggered is set by the variable resistor 19, based on the conditions of reliable switching.

, Q The allowable discharge of the capacitor 6, according to which the device is adjusted, is determined by the formula.

 H id and

michi

where C is the capacity of the switching capacitor; tg - time to recover

thyristor;

and „„ - minimum supply voltage;

Ifj is the current in the rectifier circuit. The response time of the delay element 22 is selected by the third resistor 26, based on the time of complete recharging of the commutation capacitor 6 equal to 100-150 μs. A change in the resultant resistance of the rotor circuit of the engine 1 at the time the device trips (when charging capacitor 6) does not entail a noticeable change in the drive speed, since the cycle of operation of the device for various particular conditions may vary from

units up to several tens of seconds, and the charging time of capacitor 6, dp for 100-150 microseconds, depending on the recharge current, is

no more than 0% of cycle time.

The operation of the thyristor control unit 10 is as follows.

The generator 31 start generates a sequence of pulses, the frequency of which is much lower than the operating frequency of the pulse Converter. When the handle of the controller 11 (Fig. 1) is moved to the first position (only one direction is shown, for example, forward or upward), a minimum voltage is applied to the inputs of the magnetic amplifiers 34 and 35. At the output of the magnetic power amplifier 1, the voltage U is the maximum voltage, and the output of the amplifier 35 is the minimum voltage. The generator 32 of the control thyristor switching starts working, generating a pulse with a minimum delay. Switching thyristor 5 is turned on. The main thyristor control generator 33 is not turned on until the output voltage of the magnetic amplifier 35 reaches a certain minimum value (at the second position of the controller 11 handle) of the switching thyristor 5 control generator 5 on its own the circuit is turned off and is turned on again when the start-up generator 31 is triggered, i.e. In this mode, the control pulses arrive only at the switching thyristor 5, ensuring a reliable charge of the commutating capacitor 6.

As the output voltage of the magnetic amplifier 35 increases, the generator 33 controls the main thyristor 4, which forms the maximum delay, turns on. The output signal of the generator 33 of the control by the main thyristor 4 switches on the latter, turns off the start generator 31, turns on the generator 32 of the control of the switching thyristor 5, the cycle of operation repeats. f

When the control arm of the command equipment 11 goes to the following positions and, accordingly, increases the control signal of the magnetic amplifiers 34 and 33, the delay generated by the control generator 32 of the switching thyristor 5 increases, and the delay is reduced.

generated by the main thyristor control generator 33, which corresponds to an increase in the control

When the output voltage of the magnetic amplifier 34 is reduced below a certain minimum (fifth increment of the control unit knob), the switching control thyristor 5 control generator 32 does not turn on and the signal to the switching thyristor 5 does not reach. This is the mode in which the main thyristor 4 completely shunts the power resistor I and the proposed device is put into operation.

Generators 31-33 of the thyristor control unit 10 are based on RC generators controlled by single pulses. Magnetic amplifiers 34 and 35 are self-saturation. In addition, the feedback signal from the current sensor 9 in the induction motor 1 circuit is received at the inputs of the magnetic amplifiers. standard circuitry containing current transformers and a power meter with an output filter connected to it. The signal from current sensor 9 is used to effect a current cutoff. The current cut-off pia so that when the motor current increases above a certain level, the signal from current sensor 9 becomes higher than the reference voltage, and current flows through the windings of magnetic amplifiers 34 and 35 so that the output voltage of the magnetic amplifier 34 increases and magnetic amplifier 35 is reduced, which corresponds to a decrease in the duty cycle of the operation of the pulse converter.

Thus, by using a delay element and a threshold element and their corresponding connection to a device for controlling a pulse converter in the rotor circuit of an induction motor, the reliability and efficiency of the device is increased.

Claims (1)

Invention Formula A device for controlling an asynchronous motor - containing a three-phase bridge rectifier, a power resistor, a main and switching thyristors, a switching capacitor, a recharge choke, a first diode, a stator current sensor for the asynchronous electric motor, a control unit for the main and switching type, a switch, a control device, The output of which is connected to the same input of the control unit of the main and com- Muti. thyristors, the other input of which is connected to the current-current sensor code, the outputs of the control unit of the main and switching thyristors are connected to the control transitions corresponding-. the thyristors, the point of connection of the cathodes of the three-phase bridge rectifier valves is connected to one output of the power resistor, to the anode of the main thyristor and through the switching capacitor to the anode of the switching thyristor, to one output of the rechargeable throttles, the connection point of the anodes of the valves to the three-phase bridge. connected to a different power resistor output, to the cathodes of the main and switching thyristors and to the anode of the first diode, the cathode of which is connected to another output of the recharged droselsel, three-phase input A bridge bridge rectifier is connected to a rotor circuit of an asynchronous electric motor, characterized in that, in order to improve efficiency and reliability, a threshold element composed of the first single junction transistor, the first transformer, the first and second resistors, and the second and third diodes , variable resistor and Zener diode, the first capacitor, the cathode of the Zener diode is connected to one output of the first resistor, to the gate of the first one transistor and to one output of the first capacitor, / Another output of which is connected to the anode of the Zener diode, one output of the primary winding of the first transformer and one output of a variable resistor, the other output of which is connected to another output of the first resistor and the cathode of the second diode, the anode of which is connected to the anode of the switching thyristor, the anode of the zener diode is connected to the anode of the main thyristor, the average output of the variable resistor is connected to the drain of the first unijunction transistor, the source of which is connected to another output of the primary winding of the first transformer, the secondary winding of which through the third diode and the second resistor is connected to the control junction of the commutation thyristor, and the delay element made up of the second single junction transistor, the second transformer, the second capacitor, the third, fourth and fifth resistors, the fourth and fifth diodes, one The view of the second capacitor is connected to one output of the third resistor and to the gate of the second unijunction transistor, the drain of which is connected to one output of the fourth resistor, and the source to one output primary windings of the second transformer, the other output of which is connected to another output of the second capacitor, with the anode of the fourth diode and connected to the anode of the main thyristor, other terminals of the third and fourth resistors are combined and connected to the cathode of the third diode, the secondary winding of the second transformer is connected to the control the transition of the main thyristor. Editor A.Shishkin Compiled by V.Aleshechkin Tehred L.Oleynik Proofreader I.Musk Order 4338/58 Circulation 631 Subscription VNIIPI USSR State Committee, for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, st. Project, 4 FIG. g