SU1246029A1 - Method of indirect determining of mechanical characteristic of induction electric motor - Google Patents

Abstract

The invention relates to electric machines, in particular, to methods for determining the mechanical and starting characteristics of asynchronous electric motors. The purpose of the invention is to improve the measurement accuracy of a method for indirectly determining the mechanical characteristics of an induction motor fed from a frequency converter with a braked rotor. Before starting the removal of the mechanical characteristic dp of determining the parameters affecting the measurement errors, two experiments were carried out: measuring the active resistance of the stator winding at the operating temperature and measuring the short circuit current of the engine 2 at the rated voltage and frequency. The test motor 2 is supplied from the converter 1 to a series of current values of the frequency f, and the voltage U, and measured for each value by the sensor 4, thrust force or torque. In this case, S (L yu 4 Od O to CP V5 WvSSWvVWW

Description

value 1) d, for each value depending on the stator winding resistance and short-circuit current: engine 2 is calculated according to the law and, - and, „1" t iKTlid-fl / fw) and set by converter 1 according to the indication 6 voltmeter meter and frequency meter. 7, the engine slip is then determined as S, -f, / f and

The invention relates to electric machines, in particular, to methods for determining the mechanical and starting characteristics of asynchronous linear and rotary electric motors.

The purpose of the invention is. improving the accuracy of measuring the method of indirect determination of the mechanical characteristics of an asynchronous motor, powered by a frequency converter when the rotor is braked.

The drawing shows a device for implementing the proposed method. The device includes, in itself, a frequency converter 1 with independent voltage and frequency control or with the possibility of voltage regulation within small limits at a constant frequency, the motor 2 being fixed , the secondary element 3 or the rotor, which through the sensor 4 force or moment is fixed stationary relative to the stator. The motor winding 2 is electrically connected to a frequency converter 1, an ammeter 5, a volt meter 6 and a frequency meter 7. To measure the active resistance of the stator winding motor 2, there is an 8 meter connected to motor 2 with the inverter 1 turned off and measuring instruments 5-7.

The determination of the mechanical characteristics of the proposed method is carried out in the following way.

Before starting the direct removal of the mechanical characteristic, in order to determine the parameters, the influence of the uSchp on the measurement errors, two experiments were carried out: measurement with an ohmmeter 8 of the winding resistance

build mechanical performance. The setting of the voltage value according to the indicated law makes it possible to compensate the increase in the voltage drop on the active resistance of the stator relative to its EMF and to maintain the magnetic flux of the engine corresponding to the natural mode of operation. 1 silt

0 5 o

..

five

stator at operating temperature and measurement by ammeter 5 of motor short-circuit current 2 at rated voltage and frequency.

A test motor 2 is fed to the converter from a converter 1 of the current values of the frequency f | and voltages U, and sensor 4, for each value of them, measure thrust or torque. Moreover, the magnitude of the voltage and, for each value of the frequency f .; depending on the resistance of the stator winding and the short-circuit current of the motor 2, it is calculated according to the given law and set by converter 1 according to the readings of voltmeter 6 and frequency meter 7. For measured magnitudes of the thrust or torque, the slip of the motor with respect to the measured frequency to the nominal is determined

I 1 N

and building a mechanical characteristic — the dependence of the force or moment on the slip.

Setting the voltage value as a function of the power frequency, the stator winding resistance and the short-circuit current of the motor under test according to the proposed dependence for indirectly determining the mechanical characteristics of an induction motor powered by a decelerated rotor from the frequency converter allows to compensate for the drop in voltage; on the active resistance of the stator winding relative to its. EMF and maintain the value of the magnetic flux of the engine, corresponding to the natural mode of operation. The removal of the mechanical characteristics of asynchronous cells by the proposed method with a fixed rotor allows

3

to increase accuracy, measurements for engines of various power classes and efficiency.

Claims (1)

Invention Formula The method of indirect determination of the asynchronous electric motor, powered by a frequency converter, based on changing the power frequency, measuring the tractive force or torque and power frequency when the motor is braked, defining the slip as a ratio of frequencies measured to the nominal one, characterized by In order to improve the measurement accuracy by compensating for the voltage drop across the active resistance of the stator winding, the active resistance of the stator winding is measured; closing at nominalRedaktor N.Egorova Compiled by A.Treputnev Tehred O.Sopko Order 3995/38 Circulation 728 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab. d. D / 5 Production and printing company, Uzhgorod, Projecto St., .4 12460294 voltage and frequency, tractive effort or torque is measured at a voltage, the value of which is set by the frequency converter according to the law  n , " De, -, .i. „ IK-current and nominal linear voltage of the motor; - current and nominal power frequency of the engine; -phase motor short-circuit current at nominal voltage and frequency; -active phase resistance of the stator winding. Proofreader V.Sinitska