SU1328918A1 - Alternating current electric drive - Google Patents

Abstract

The invention relates to electrical engineering and can be used in electric drives of conventional mechanisms. The aim of the invention is to improve the accuracy of regulation. nor rotation frequency. This goal is achieved by the fact that the slip frequency measurement unit 3 of the electric motor is pulsed, and a shaper 4 pulses are inserted into the electric drive, a counting trigger 5, signals from which pass through the master frequency generator 6 and carry information about the set value of the rotor rotation frequency, which is compared in a logical element AND 10 with a valid value of the rotor speed. As a function of this error, the duration of the control pulses at the input of the thyristor switch is formed until the drive drives to work out the resulting error in the rotation frequency of the engine. 2 Il. d het U, t 00

Description

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

The purpose of the invention is to improve the accuracy of rotational speed control.

FIG. 1 shows a functional diagram of the drive; in fig. 2 - voltage diagrams.

The AC drive contains a three-phase asynchronous motor 1, a thyristor switch 2 connected to the stator winding phase of the motor, a motor measuring unit 3 measuring the slip frequency of the motor, pulsed, the driver 4 pulses, the output connected to the input of the counting trigger 5, the output of which is connected to the generator input 6-master frequency, made in the form of a series-connected differentiating unit 7 and a continuous multivibrator 8.

The output of the oscillator 6 of the master frequency is connected to the input of the inverter 9, the output of which is connected to the first input of the logic element AND 10, the second input of which is connected to the input of the generator 6 of the driving frequency, the output of the logic element And 10 through the expander 11 pulses connected to the input of the amplifier 12, the output of which is connected to the output of the initial startup unit 13 and to the control input of the thyristor switch 2.

The drive works as follows.

When the supply voltage is turned on, a starting pulse appears from the control input of the thyristor switch 2 and from the initial start-up unit 13, which gives the initial impetus to the rotation of the motor 1. The output of the frequency-slip unit 3 causes the pulses and 5 formed by the duration of the shaper 4 pulses, which arrive at the counting input of the trigger 5, the forward output of which produces rectangular pulses and equal in duration to the distance between two neighboring HHMii pulses 14- 15 and 16-17 (Fig. 2), with pauses between them equal to the distance between pulses 15 and 16.

The sequence of rectangular pulses Uj goes through differentiating unit 7 to the trigger input of the waiting multivibrator 8, which is triggered by the leading edge of each of the incoming pulses Uj and output pulses of a given width U at its output, which is tuned by selecting the control voltage U

The width of the pulses U is the setting of the rotor speed, since the difference in the travel of the rear edges of the pulses Uj and, resulting from their comparison, with the aid of the logic element 10 and the inverter 9 is fed to the input of the pulse extender 11, providing the duration

0 control pulses at the input of the thyristor switch 2. U T where T, is the period of the supply voltage (for asynchronous motors with a short-circuited rotor T 0.02 s.

5 The output signal of the expander 11 of the pulses через through the amplifier 12 is fed to the input of the thyristor switch 2, which is held in the on state until the regulating system does not work out the resulting error in the rotation frequency of the engine.

Due to the fact that as the frequency of rotation of the electric drive increases, the frequency of the pulses U. from the pulse sensor of the slip frequency measuring unit 3 of the electric motor increases, for the considered control system, the ratio of i and i is characteristic.

For a known device, since the frequency of the rotor voltage decreases with increasing rotational speed, the ratio and / U, j is characteristic.

The latter circumstance caused a definite change in the construction of the rotational speed control unit. 0

Fore, Mula Invention

AC drive, 5 containing a three-phase asynchronous motor, a thyristor switch included in the stator winding phase of the motor, a slip frequency measuring unit of the motor, a frequency generator, the output of which is connected to an inverter, the output of which is connected to the second input the input of the master frequency generator is connected, it is about start, pulse shaper, counting trigger, pulse expander and usiU.

Editor P.Geershi

Compiled by E.Peremyslova Tehred M.Morgental

Order 3496/56

Circulation 659 Subscription

VNIIPI USSR State Committee for Inventions and Discoveries 4/5, Moscow, Zh-35, Raushsk nab. 113035

Production and printing company, Uzhgorod, st. Project, 4

and the slip frequency measuring unit is pulsed and connected to the pulse driver input, the output of which is connected to the input of the master frequency generator through a counting trigger, the output of the logic element I is connected to the amplifier’s output through the pulse expander and the output of the initial start unit and with a control input of a thyristor switch.

Proofreader V.Girn to

Claims (1)

Claim An AC drive containing a three-phase asynchronous motor, a thyristor switch, included in the phases of the stator winding of the electric motor, a block for measuring the slip frequency of the electric motor, a driving frequency generator, the output of which is connected to the inverter, the output of which is connected to the first input of the AND gate, with the second input of which the input of the generator of the driving frequency is connected, characterized in that, in order to increase the accuracy of speed control, an initial start-up block is introduced ka, pulse shaper, counting trigger, pulse expander and amplifier, and the slip frequency measuring unit is made pulse and the output is connected to the input of the pulse shaper, the output of which through the counting trigger is connected to the input of the driving frequency generator, the output of the logical element And through the pulse expander is connected to an amplifier input, the output of which is connected to the output of the initial start-up unit and to the control input of the thyristor switch.