SU797046A1 - Method of regulating electric motor current - Google Patents

Description

one

The invention relates to electrical engineering, in particular to direct current drives with thyristor converters.

A known method for regulating the current of an electric motor, regained in an electric drive, is concluded in that they compare the current and set current values of the motor and, by comparison, switch the power of the motor ij. Pulsations of the motor current can be reduced by increasing the frequency of switching the motor supply, which limits the use of thyristor converters as a switching device.

The closest to the invention to the technical essence is a method of controlling the current of an electric motor that is supplied from a thyristor dc converter, which consists in comparing the current and set values of the electric motor currents and, by comparison, switches the thyristor converter, and introduces a delay for switching on the converter and limit the maximum, the frequency of his work 1,2.

However, due to the significant ripple of the motor current, the quality of the overall current control is reduced. The purpose of the invention is to increase

quality control current of the motor.

The goal is achieved by the fact that, according to the proposed method, the engine's anti-EMF is measured and the thyristor converter's turn-on delay is formed as a function of the measured back-EMF.

Figure 1 shows the structure-diagram of the device, realizing

the proposed method; figure 2 a, b diagrams of his work.

The device (see Fig.1) contains the unit 1 current, the output of which is connected to the input of the zero-body 2, the second

Claims (2)

the input of which is connected to the output of the pulse sensor 3 of the motor current. The zero-organ output Z is connected to the inputs of the pulse generator 4 and the variable delay unit 5, the output of which is connected to the input of the driver 6 of the thyristor control thyristor converter 7. The thyristor converter 7 contains one working thyristor 8 and the switching device 9, to the input which is connected to the output of the imager 4 pulses. At the output of the thyristor converter l 7, the electric motor 10 is connected to the output of the sensor 11, the counter-EMF of which is connected to the auxiliary input of the block 5 of variable delay . The device works as follows. Let unit 5 of variable delay 5, as the back-EMF of the electric motor 10 increases, reduce the delay time of the pulses for switching on the converter 7 from the maximum value u.t to the minimum utgi. When the thyristor converter 7 is turned on in the start mode, the electric motor of the motor increases rapidly and slowly drops off when it is turned off. Suppose now that the current setting device 1 is set such a value that the switching of the thyristor converter 7 occurs at the maximum frequency determined by its final parameters. When the working thyristor 8 is turned off, the current of the electric motor 10 decreases and becomes less than the set value D (see Fig. 2a), and the signal of the current sensor 3 is less than the signal of the current setting device 1. The zero-organ stops generating pulses arriving at block 5 of the variable delay, and at the output of the latter, the signal Uj- is absent. With delay At 5, a variable delay time unit transmits a signal to the driver 6 of the control pulses of the working thyristor, which includes the working thyristor. 8 and therefore the power of the motor. The motor current begins to increase and again reaches a value of 3. In this case, the signal of current sensor 3 becomes equal to the magnitude of the signal, current 1 setpoint, and zero-body 2 begins to generate a pulse and resets the signal Uy at the output of block 5 of variable b to zero, and if time elapsed pulses and equal to the minimum switching period of the converter 7, stops the supply of pulses to the switching device 9, the latter includes the working thyristor 8 and the electric motor 10. The motor current begins to decrease. Further, the processes are repeated. In the considered case, the null-organ interference does not result in the surge of the motor current, since the zero-organ signal is blocked by a variable delay unit for a time sufficient to prepare the converter for disconnection. At the same time, the current pulsations are insignificant due to its slow speed of decay. Suppose now that the electric motor 10 has accelerated and the motor current increases slowly when the converter 7 is turned on, and when it is turned off, it quickly decreases (see Fig. 2b). Consequently, the signal from the output of the sensor 11 increases, which causes a decrease in the delay time of the operating thyristor control pulses to the minimum value tj, ensuring the minimum current drop of the electric motor 10. In the generator braking mode of the electric motor 10, the device is similar, however, the variable delay block 5 sets the minimum delay on switching on of converter 7 at zero value of counter-emf and increases it with the growth of the latter, since the motor current at high values of counter-emf it melts quickly and falls off slowly. Thus, the quality of regulation is improved due to a decrease in current ripple and noise immunity of the electric drive as a whole. Claims The method of controlling the current of an electric motor supplied from a thyristor converter of direct current consists in comparing the current and set values of the electric motor currents and according to the results of the comparison switch the thyristor converter, and introduce a delay to turn on the converter and limit the maximum one. the frequency of its operation, that is, so that, in order to improve the quality of current control of an electric motor, the motor's counter-emf is additionally measured and a delay is generated to turn on the thyristor converter as a function of the measured counter-emf. Sources of information taken into account in the examination 1. L. D. Pankratyev and others. Pulsed and relay follow-up DC drives with semiconductor amplifiers, M., Energie, 1969, p. 35-37. 2. USSR author's certificate No. 364061, cl. H 02 R 7/28, 1970.