SU1559305A1 - Method of measuring phase angle of induction motor rotor - Google Patents

Abstract

The invention relates to electrical measurements and can be used in electric drive control systems. The aim of the invention is to simplify the method of measuring the rotor angle of an asynchronous electric motor — the phase angle between the supply voltage and the rotor current of the asynchronous electric motor. The method is based on measuring the voltage of the power supply and the current consumption of the electric motor. The stator current is determined in accordance _with the formula J = ^U. L ^-JARCTGX / ^R ) / (√ ² -X ² ), where R and X are the active and reactive resistances of the stator winding

J _c and U ¹ are the complex values of the stator current and supply voltage, for which a phase shift equal to -ARCTGX / R is introduced into the current phase of the power supply voltage, and the amplitude of the received signal is reduced by √R ² + X ² times. By subtracting the stator current from the current consumption, the rotor current of the induction motor is determined. The phase angle is defined as the phase difference between the voltage of the power source and the rotor current.

Description

The invention relates to electrical measurements and can be used in electric drive control systems.

The purpose of the invention is to reduce the speed of measurement of the rotor angle of an induction motor.

The current consumption of an asynchronous motor is determined by the formula

 + Ip,

(one;

where 1C is the asynchronous stator current

electric motor; 1p is the rotor current of the asynchronous electric motor.

If we know the magnitudes of the active R and reactive X resistances of the stator winding (these values are given in the passports or catalogs of electric motors), the impedance of the stator winding can be calculated as

. (2)

Z value can be written in the form (3)

The amplitude of the vector of the impedance Z of the stator is

JV JV

wed

OE O SP

 V

R + X2

(four)

The angle of the complex resistance vector Z of the stator is equal to

at

u arrtg -.

(five)

Then the stator current vector I,

t M J A e

(6)

where U is the voltage vector of the power supply.

Equation (1) determines the rotor current vector 1p

(7)

If you know the values of U and I „, it is possible with the help of a phase meter to easily measure the phase angle between them.

The angle of the rotor of the induction motor is measured as follows.

1. According to the known values of the active R and reactive X resistances of the stator winding, the amplitudes A and the angle c of the vector resistance of the stator winding are calculated by the formulas (0 and (5)).

2. Measure the values of the voltage U of the power source and the current IQ of an asynchronous electric motor.

3. The amplitude of the measured value of the voltage of the power supply is reduced by A times, where A is determined by the no-formula (s) and the phase shift c / calculated by the formula (5) is added to the current phase of the power supply voltage.

0

five

0

0

five

0

By deducting from the current consumption of the asynchronous motor 1a, the value defined in paragraph (3) 5 calculates the rotor current of the asynchronous motor 1p.

5. Measure the phase angle of the rotor, defined as the phase difference between the voltage of the power source and the rotor current of the induction motor.

The proposed method allows, by simple means, to determine the phase angle of a jf-synchronous motor .i

Claims (1)

Invention Formula ( A method for measuring the rotor phase angle of an asynchronous motor based on measuring the supply voltage and current consumption of an asynchronous motor, characterized in that, in order to reduce speed, the stator winding current is determined by adding to the current phase the voltage of the power source of the phase angle previously calculated from formula jj -aretg -, where X - reactive; R - to active resistance of the stator winding, and reducing the amplitude of the power supply voltage by a factor of three, determine the rotor current as the difference between the current consumption of the induction motor and the stator current, measure the phase angle as the phase difference between the voltage of the power source and the rotor current of the induction motor.