SU106863A1 - Adjustable AC Drive - Google Patents

Description

An adjustable electric drive with asynchronous motor and private control is most promising in terms of speed and reliability, but it has limited application due to the imperfection of frequency converters. As the latter are used, as is known, multi-phase compensated

collector generators or asynchronous converters. The frequencies of which the reactive power of the excitation is up to 15-20% of the iii of the power of the machine.

The aim of the present invention is to reduce the excitation power of the collector alternators with the automatic reproduction of the necessary law of change in the voltage of the asynchronous motors.

For this purpose, it is proposed to use electric machine amplifiers with a transverse heading and additional capacitors in the transverse and longitudinal chains as alternators.

FIG. 1, 2 and 3 shows the scheme of the proposed electric drive in

three variants; in fig. 4 and 5 diagrams of switching on the motor-car amplifiers, which play the role of alternators.

In the first variant, the normal asynchronous motor ID is switched on at start-up as a three-phase motor from a conventional constant-frequency network with a KP contactor, and then switches over to a power supply from a rotor contactor using an AC contactor operating as an alternator. Prk this engine whose ID works as an asynchronous single-phase motor according to a star circuit with one free phase or a triangle circuit, one of the vertices of which remains free when switching to single-phase power. Regulation of the speed of rotation of the motor ID in this mode is provided by changing the frequency of the current supplied by the electric amplifier with the help of the frequency sensor of the frequency response included in its setting winding OB.

In order to obtain the necessary for the drive current pepemenno o approximately linear dependence on the frequency of the voltage at a constant MotuHocTH pozbuzhdeni, the transverse chain ECU included emkoyt G2, compensating induktipnbst poperechkon obesPechIpayushay resonance circuit and by poperech11oy chain at a frequency slightly (by 5-10% ) exceeded the maximum operating frequency of the drive. In this way, the operation of the ECU is carried out at sunrise and resonant PETP. To reduce the gain of the EMU at low frequencies, an additional resistance RD is connected in parallel with the capacitance Cr. As the frequency increases, this resistance is switched on by the contacts of the frequency relay P. To adjust the characteristics of the voltage of the ECU, parallel to its control winding, ОVg, another capacitor Ci is turned on, tuned to the intermediate resonant frequency. This results in an increase in the voltages in the initial part of the curve, and a slight decrease in hippres in the high frequency zone. The field windings and the capacitors Ci and Cg of the motor-amplifier can be switched on according to the schemes in FIG. 4 and 5. The main circuit diagram in FIG. five; the circuit in FIG. 4 is intended for use in AC EMU systems without additional DC windings in a transverse circuit. In a two-phase or three-phase power supply system for electric motors (Figs. 2 and 3), the Poison engine operates from a two-machine or three-machine unit consisting of two or three EMU transverse floors connected in a star or triangle. The engine is started by increasing the frequency and voltage of the ECU. The reverse of the motor is carried out by changing the phase alternation set by the D / AC excitation frequency sensor. Various known devices can be used as a frequency sensor: for small powers, electronic generators and generators with magnetic amplifiers, for medium and high power systems, electronic generators. 1. Adjustable AC drive consisting of one or more collector AC generators, forming a single-phase or multi-phase system, and asynchronous short-circuited electric motors, characterized in that, in order to reduce the Excitation Power in the case of necessary mathematics changes in the supply voltage of asynchronous motors, as indicated collector generators used electric intensifiers (EMU) transverse floor, working with independent excitation by alternating current of variable frequency. 2. Adjustable electric drive according to claim 1, characterized in that, in order to obtain an approximately linear dependence of the voltage of the electro-amplifiers on the frequency at a constant excitation power, capacitors are included in the longitudinal and transverse circuits of the ECU.

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FIG. 3