SU1654963A1 - Frequency-controlled electric drive - Google Patents

Abstract

The invention relates to electrical engineering, namely, to frequency-controlled electric drives based on asynchronous short-circuited motors and direct frequency converters (NFC). The purpose of the invention is to improve the quality of control by reducing the constant and subharmonic components in the motor phase currents. The goal is achieved by introducing analog adders 13, 14, installation node 15, analog amplifiers 16, 17, 18, and limiting amplifier 19, the output of which is connected to the input of the magnetizing current setting of the coordinate conversion unit 13. At the same time, it is possible to correct the magnetizing current of the induction motor 1 as a function of the current rotational speed and load (active component of the stator current), thereby reducing the intercommutation interval in the falling portion of the EMF, the number of current pulses in the half-period increases and the shape of the Aastok is improved. 3 il.

Description

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Claims (1)

Formula of the invention A frequency-controlled electric drive containing an asynchronous squirrel-cage motor, to the stator windings of which are connected the outputs of an adjustable current source based on 1 direct frequency converter ', a pulse speed sensor mounted on the shaft of an asynchronous squirrel-cage motor, magnetizing current adjuster, speed controller, voltage converters - frequency and frequency voltage ,, threshold element, first analog adder, digital harmonic driver of signals, the EMF driver and the coordinate conversion unit, whose active current input is connected to the output of the speed controller, the inputs for harmonic signals are combined. in phase with the corresponding first two inputs of the EMF driver and connected to the outputs of the digital harmonic signal generator, and the outputs of the coordinate conversion unit connected to the first pair of inputs of an adjustable current source, the second pair of inputs of which are connected to the outputs of the EMF driver, while the third input of the EMF is connected to the output of the first analog adder, one of the inputs of which is connected to the input of the voltage-frequency converter, with the input of the threshold element 40 and connected to the output of the speed controller, the output of the frequency-voltage converter is connected to the other input of the first analog adder and to one of the inputs speed controller 45, another input, which forms the job speed input, the voltage-frequency converter outputs and a threshold element are connected to the first pair of 50-digital inputs th harmonic signal generator, the second pair of inputs which are combined with the corresponding inputs of the inverter frequency - voltage and is connected to the outputs of the pulse coupled to the input output pulse speed sensor, wherein. that, in order to improve the quality of control ⁹ 1654963 10 by reducing the constant and subharmonic components in the phase currents of an asynchronous squirrel-cage motor, a second $ and third analog adders, a set point, three analog amplifiers and a limited amplifier whose output is connected to the reference input are introduced magnetizing current of the transformation unit ^ coordinates, while the inputs of the first and _; the second analog amplifiers are connected respectively to the output of the setter, the magnetizing current and the output of the speed controller, the input of the third analog amplifier is connected to the output of the setpoint node through the second analog adder, the other input of the second analog adder is connected to the output of the frequency-voltage converter, and the outputs of analog amplifiers connected ^ to the inputs of the third analog adder, connected by the output to the input of the amplifier with restriction.