SU1534729A1 - Device for regulation of electric motor current - Google Patents

Abstract

The invention relates to electrical engineering and can be used to discretely regulate the current of an electric motor. The aim of the invention is to improve the quality of the consumed current by reducing the range of variation of the frequency of regulation. The device contains a control key 1 and a current measuring transducer 2 for connecting a motor to the rotor circuit. At comparator 5, a reference voltage, proportional to the setpoint current, is compared with the output signal of the sawtooth driver 4, the frequency of which depends on the measured motor current. With an increase in the current control frequency of the core, the output voltage of the frequency-analog converter 11 increases and the control signal delay time increases proportionally due to the introduction of the delay node 12. At the same time, the switching frequency of the key 1 is almost constant, while retaining the advantages of the relay control method. 2 Il.

Description

I The invention relates to electrical engineering and can be used to discretely control the current of a motor.

The purpose of the invention is to improve the quality of the consumed current by reducing the range of measurement of the frequency of regulation.

FIG. 1 shows a block diagram of the device; in fig. 2 - timing charts of the device.

The device contains a key 1 and a measuring transducer 2 gok Intended for switching on an electric motor 3 in the crank circuit. to the output of the measuring transducer 2 current. The second voltage source 8 is connected to the second comparator 5, and the control input of switch 1 is connected to the output of power amplifier 9. In addition, the device contains serially connected second trigger 10, a frequency-analog converter 11 and an adjustable delay node 2. Single-input input 13 is connected to the output of the measuring transducer 2 current, and output - With the second input of the first trigger 6, the first input of which is connected to the first input of the second trigger 10. The second input of the second trigger 10 is connected to the output of the logic element And 7, and the output of the trigger 10 is connected to the second input node 12 adjustable delay, the output connected to the input of the amplifier 9 power.

The device works as follows.

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At the initial moment of start-up, the motor current is zero and the current measuring transducer 2 generates a pulse voltage 14 (FIG. 2) of rectangular shape with an initial oscillation frequency G0.

Pulse voltage 14 is fed to the inputs of the former 4 sawtooth voltage, one-shot 13, the logic element And 7.

Over the voltage half period 14, a sawtooth voltage 15 is formed, which is fed to the input of the comparator 5, where it is compared with the reference voltage Uon, corresponding to the setpoint current. At a voltage of 15 7UoR. at the output of the comparator 5, logical 1 voltage 16 is formed, which, entering the inputs of the flip-flops 6 and 10, sets them into one stable state. 17-voltage from the output of the single-shot 13, 18 - voltage from the output of the trigger 6.

As follows from the timing diagram (Fig. 2), the voltage 19 at the output of the element 7 corresponds to a logical O, the voltage 20 at the output of the trigger 10 is set to zero.

Voltage 20 is supplied to the frequency-analog converter 11 and variable-delay node 12. Voltage 21 at the output of the frequency-analog converter 11 is zero at the time of start-up, because during the first adjustment period information on the current adjustment frequency is 2 does not arrive.

The output voltage 22 of the node 12 of the adjustable delay, equal to logical 1, through the amplifier 9 enters the controlled key 1 and opens it. The first voltage pulse 22 is identical to the inverted voltage pulse 20.

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After starting the motor 3 from the fixed state, the current 23 of the motor 3 and the frequency of the voltage pulses 14 increase. The amplitude of the sawtooth voltage 15 decreases and when the comparator 5 stops the formation of voltage pulses 16 and it is 1,

Voltage pulses 14 triggers a one-shot 13, voltage 17 from the output of one-shot 13 sets trigger 6 to another stable position at which voltage 18 is 1. Input to trigger trigger 10 is received by voltage pulses 14 of current measuring transducer 2 through a logic element And 7 (voltages 14, 18, and 19).

The trigger 10 is set to another steady state with a logic voltage 20 at the output equal to I. The magnitude of the output voltage 21 of the frequency-analog converter 11 remains unchanged, as follows from the timing diagram (Fig. 2), the voltage 22 becomes equal to 0, coincides in time with the inverted voltage 20 and through the amplifier 9 closes the key 1.

The current 23 cor and the frequency of the voltage pulses 14 decrease, the amplitude of the voltage 15 increases, and at 15 / -Uon, a voltage pulse 16 forms at the output of the comparator 5, setting triggers 6 and 10 to their original state.

Thus, the serially connected frequency-analog converter 11 and the variable delay node 12 do not affect the initial switching frequency of the controlled key 1 by the voltage pulses 22 at the output of the node 12 without delay relative to the voltage pulses 20. The initial switching frequency of the key 1 is determined The width of the hysteresis zone of the comparator 5 and the delay of the control signals to turn on and off the key 1, which depends on the relative position of the pulses 14 of the measuring transducer 2 current and torque to achieve a controlled current 23 1y set current level. As it follows from the time diagrams (Fig. 2), for voltage pulses 14 and controlled current 23, the latency value may vary.

c from the half period to the period following voltage pulses 14.

With an increase in the frequency of the regulator or the current of the motor 3, the output voltage 21 of the frequency-analog converter 11 increases and the delay time of the control signal 10 22 relative to 20 increases by a time interval t (Fig. 2). At the same time, the frequency of current regulation of the core will slightly differ from the value of the frequency in the steady state operation.

15 The device provides an increase in the quality of the consumed current, which is achieved by providing a practically constant switching frequency of the semiconductor key, which is limited to the level allowed by the switching properties of the controlled key and the power system, while maintaining the positive properties of the relay control method. As a result, the working conditions of the filters are improved, their weight and dimensions are reduced.

By using the proposed device, in particular for controlling the current of an electric rolling stock engine, the effect of a powerful impulse load on signaling and communication devices is reduced.

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Claims (1)

Invention Formula A device for controlling the current of an electric motor, comprising a controllable key and a current measuring transducer for connecting the electric motor to the core circuit, an output of the current measuring transducer through serially connected sawtooth generator, a comparator and a trigger connected to the first input of the logic element I, the second input of which is connected to the output of the current measuring transducer, to the second input of the comparator is connected the source of the reference voltage, and the control input The key is connected to the output of a power amplifier, characterized in that In order to improve the quality of the current consumed by reducing the range of the variable frequency of the regulation, a second trigger connected in series is introduced into it, a lot converter and a variable delay node, as well as a single-conductor input connected to the output of the current measuring transducer, and output to the second input of the first trigger, the first input of which is connected to the first input of the second trigger, the second input of which is connected to the output of the logic element I, and the output is connected to the second input of the adjustable delay node, the output connected to the input of the power amplifier. FIG. I