SU1339856A1 - Apparatus for controlling rotary speed of induction motor with phase-wound rotor - Google Patents

Abstract

The invention relates to electrical engineering, can be used in electric drives of generally accepted mechanisms. The purpose of the invention is to improve the accuracy and speed of adjustment. The device contains resistors 2 in the rotor circuit, triacs 3, synchronization unit 4, generator of 7 voltage signals, comparator 5, control pulse shaping unit 6, task unit 10, adder 11, amplifier 12, matching stage 8 and sensor 9 rotational speed, the control voltage shaping unit 13 provides the saw blade inclination of the sawtooth generator when the frequency of the current in the rotor circuit of the motor 1 is changed, which improves the control accuracy. Increased speed is ensured by eliminating a smoothing filter, 3 sludge. c (L OO 05 CO 00 cd O5

Description

The invention relates to electrical engineering and can be used in electric drives of conventional mechanisms.

The purpose of the invention is to improve the accuracy and speed of regulation

FIG. 1 shows a block diagram of the device; in fig. 2 is a circuit diagram of a saw-voltage generator; in fig. 3 is a schematic diagram of a control voltage shaping unit.

A device for controlling the rotational speed of an asynchronous motor with a phase rotor contains a three-phase resistor 2 in the rotor circuit, phase-wound by triacs 3, a synchronization unit 4 with three inputs and three outputs, three comparators 5, three control pulses 6, three sawtooth generator 7, matching stage 8, rotational speed sensor 9, task block 10, adder 11, amplifier 12, rotational speed sensor 9 is mechanically connected to the shaft of an asynchronous body 1 with a phase rotor and its output is connected to the matching stage 8, one output of which is connected to one input of the adder 11, another input of which is connected to the exp code of the task block 10, the output of the adder 11 through the amplifier 12 is connected to one inputs of the comparators 5, the output of each comparator 5 is connected to the control the corresponding electrode of the corresponding triac 3, the inputs of the synchronization unit 4 are connected to the corresponding power pins of the triacs 3, the outputs to the first inputs of the corresponding generators 7 of the sawtooth voltage, the outputs of the cat They are connected to the second inputs of the respective comparators 5, the control voltage generation unit 13, the input of which is connected to the output of the matching stage B, and the output to the second inputs

I will give generators 7 sawtooth, for example, cc rotor. Thus compensated.

The sawtooth generator 7 (Fig. 2) is based on a field-effect transistor 14, an operational amplifier 15 and a bipolar transistor 16.

The control voltage generating unit 13 is provided on the operational amplifier 17.

55

The negative influence on the control angle "variable frequency of the rotor current and the linearity of the adjustment characteristic o (f (U),

In the comparator 5, the sawtooth voltage is compared with the voltage supplied from the amplifier 12, and at the moment of their equal output 5

0

five

The device works as follows.

When the supply voltage is applied to the stator windings of the asynchronous motor 1 and at the set voltage Uj O, the operating point is determined by the limiting rheostatic mechanical characteristic of the motor with the resistor 2 introduced into the rotor circuit and the characteristic of the production mechanism. In this case, the control unit generates and supplies to the control electrodes of the triacs 3 only the clock pulses received when the rotor current passes through zero.

For operation at the selected speed, in block 10, the task is set by a control voltage corresponding to the selected rotation frequency, which with a certain tempo arrives at the first input of the adder 11. At its second input, feedback voltage is applied from the matching cascade 8 and. Difference of driver and feedback voltages

UZ - Uo, Li

0

five

0

five

Reinforced

enters the amplifier 12. The voltage (Ul,) is applied to one of the inputs of the Comparators 5 of the three control channels. The second inputs of the comparators 5 receive a linear falling sawtooth generator oscillator 7, synchronized with the rotor current frequency due to the operation of synchronization unit 4, which produces sync pulses when the rotor current passes through zero, applied to the second inputs of sawtooth generator 7. The first inputs receive control voltage from block 13, which gradually decreases in magnitude during acceleration of engine 1 to a predetermined rotational speed. This voltage automatically changes saw inclination as the speed of engine 1 increases and the frequency of the motor decreases.

The negative influence on the control angle "variable frequency of the rotor current and the linearity of the adjustment characteristic o (f (U),

In the comparator 5, the sawtooth voltage is compared with the voltage supplied from the amplifier 12, and at the moment of their equality a control pulse is generated. In block 6, this pulse is amplified and supplied to the control electrodes of the triacs 3 which, when turned on, shunt the phases of the resistor 2 to each half-period of the rotor voltage. There is a smooth acceleration of the drive at a selected rate to a predetermined rotational speed. With an increase in the voltage setting, the control angle smoothly decreases from 180 ° to the value determined by the voltage set in the task set 10. The operating point of the steady state is determined by the intersection of the 15th switch in the circuit of the alternating mechanical characteristic of the rotor production, the mechanical mechanism and the artificial mechanical characteristic of the engine 1, corresponding to the equivalent incremental active resistance 20, which is proportional to the switching duty cycle. Duty cycle

Claims (1)

Invention Formula An apparatus for controlling the rotational speed of an asynchronous motor with a phase-rotor, containing a three-phase resistor in the rotor circuit, phase-locked by a triac, is determined by the angle of adjustment and the switching period. In the steady state, the rotation speed of the motor 1 is constant, respectively, the constant value of the feedback voltage U and the output of the block 13 is removed, the constant value of the control voltage is proportional to the steady-state frequency of the rotor current. At the same time, the constant value of the second control voltage is removed from the output of the amplifier 12. In the case of a load disturbance in the system, for example, an increase in the moment of resistance, the closed system of automatic control with a hard negative feedback on the rotation frequency will react accordingly: in the dynamics the rotation frequency will decrease, the voltage difference will increase: after amplification, it is fed to the input of the comparator 5, where the control pulse will be shifted downwards control angle d, which will cause a decrease in the average value of the equivalent resistance of the rotor circuit and an increase in the current and, accordingly, of the motor torque. In this way, a constant rotational speed is maintained. The change in voltage at the output of the unit is insignificant since the gain in it is equal to 1. The stiffness of the mechanical characteristics of the electric drive mainly depends on the value of the gain and the circuit of the amplifier 12, which in the proposed device is taken as typical. The control system works in a known manner in the event of a decrease in load. Thus, the introduction of a control voltage forming unit into the proposed device makes it possible to obtain a higher-quality operation of an asynchronous electric drive with a thyristor switch in the rotor AC circuit, Invention Formula switch in the AC rotor circuit, An apparatus for controlling the rotational speed of an asynchronous motor with a phase-rotor, containing a three-phase resistor in the rotor circuit, phase-locked by a triac, synchronization unit with three outputs, three sawtooth voltage generators, three comparators, three control pulse formers, a matching stage, a rotational speed sensor, the task unit, the adder, the amplifier, the rotational speed sensor is mechanically connected to the shaft of an asynchronous motor with a phase-rotor and the code of the rotational speed sensor is connected to the input matching stage, one output of which is connected to one input of the adder, another input of which is connected to the output of the task block, output of the adder through a divider is connected to one input of the comparators, the output of each comparator is connected to the control electrode of the corresponding triac through the corresponding driver, the inputs of the synchronization unit are connected to the corresponding power pins of the triacs, the outputs to the first inputs of the corresponding sawtooth generators, whose codes are connected to The second inputs of the respective comparators, characterized in that, in order to increase accuracy and speed, a control voltage generating unit is inserted into it, the input of which is connected to the output of the matching cascade, the output of the control voltage forming unit is connected to the second input of each sawtooth voltage generator. bycod 3 Um-uoc tJy & ь () (one Editor L. Gratilllo Compiled by V. Aleshechkin Tehred L. Serdyukova Proofreader A. Obruchar Order 4243/54 Circulation 659 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