SU1327024A1 - Method of indirect check of irregularity of air gap of induction motor - Google Patents

Abstract

This invention relates to the field of electrical engineering. The aim of the invention is to improve the accuracy and reduce labor costs for controlling the air gap of an induction motor. The method measures the temperature of the rotor winding before short-term connection of the motor to the network and at the time of shutdown with a positive acceleration value during acceleration it measures the constant decay time of the transient current in the rotor and comparing the superheat temperature of the rotor with the constant time of the decay of the rotor current baseline values are judged to change the non-equal, dimensionality of the air gap. with (L

Description

one

The invention relates to electrical engineering and can be used to control the non-uniformity of the air gap of a rotor induction motors.

The purpose of the invention is to improve the accuracy and reduce the labor costs of controlling the air gap of an asynchronous motor with a phase-rotor.

The essence of the invention is that measuring the temperature of the rotor winding, which is assumed to be equal to the ambient temperature, connect an unloaded asynchronous motor to the operating voltage network and control the frequency of its rotation during the acceleration of the rotor when it is positively accelerated, disconnect the motor from the mains at the rotor speed within 0.5-0.95 nominal values, determine the temperature of the rotor winding at the moment of shutdown and the current damping constant and in the rotor, and by comparing the rotor overheating temperature and the constant time of the rotor current with the baseline values, a change in the unevenness of the air gap is determined.

The winding temperature at the time the motor is disconnected from the network in the control (tj,) and base (tg) experiments is determined, for example, using the expression to take into account the overheating of the rotor winding during the start of the unloaded engine,

 The effect of temperature changes on the active resistance of the rotor is taken into account according to the well-known formula

The change in the current in the rotor is carried out using measuring shunts connected in series to the circuit of each phase rotor winding (between the rings and the additional resistance). The determination of the diagnostic parameter — the constant decay time of the transient current in the rotor — is made by the change in time of the imaging current vector in the rotor.

As a diagnostic signal, it is also possible to use the current of one of the phase windings of the rotor, which has the highest initial value of the transient current.

The constant decay time of the transient current in the rotor is determined by the well-known expression.

ten

27024. 2

The number of measurements and the time interval between the measured; 1 mi, it is advisable to take on the basis of the approximate value of the constant time, equal to 1/3 of the decay time of the transient current in the rotor to 0.05 1 p. starting from the moment the motor is disconnected from the mains. During a specified period of time, 8-16 current measurements and corresponding time coordinates, measured from the first measurement, should be made, which are made after the initial current (IP) decreases no less than twice as much as its value at the time the engine is disconnected from the network. This ensures the non-saturated state of the path of the main magnetic flux and, therefore, eliminates the dependence of the constant decay time of the current in the rotor on the magnitude of this current.

The connection of the non-uniformity of the air gap (eccentricity) with the constant decay time (T) of the free transient current in the rotor of an asynchronous motor follows from the analysis of the expression

t - lp -i 5ifii)

A - f

15

20

thirty

where is x

35

0

five

X (f)

(ABOUT

f

Gr is the inductance of dissipation and the active resistance of the rotor winding; mutual induction resistance between stator and rotor windings;

 - eccentricity of the rotor, determined according to the metric measurements of the Maximum ("dKc) minimum (;" cent) values of the air gap between the rotor and stator in the end sections of the stator bore.

50

Since the inductive resistance of the mutual induction of an asynchronous motor is more than an order of magnitude greater. inductive resistance of the scattering rotor winding, and the latter is about 55 but equal to the inductive resistance of the scattering of the stator winding, then with a very small error

t -

T —r; (2)

where is synchronous inductive

asynchronous motor resistance

Taking into account the change in the thermal mode of the engine in the control experiment as compared with the base conditions, the relative value of constant time is equal to

k + tj k + tg

   about

 T,

where t and tg are the temperature values of the rotor winding at the control and base measurements;

T and Tg are the time constants in the control and baseline experiments;

k is the coefficient depending on the material of the rotor winding (k 235 for copper and k 245 for aluminum).

The change in T o in the rotor eccentricity function for asynchronous motors having more than one pole pair in the absence of saturation of the path of the main magnetic flux occurs according to a linear law. With this increase. from O to 100% leads to a corresponding increase in these values from 1 to 1.2 rel. units

Using dependency X

 5-0

 f (), obtained by displacing the rotor axis parallel to the bore axis of the stator, to determine the performance characteristics, allows you to determine the maximum eccentricity for the field at the control experiment, the values of T o X, o taking into account Not only eccentric, but also all possible spatial arrangements of the axis rotor relative to the axis of the stator bore,

In accordance with the indicated performance characteristic, when e is changed from 0 to 100%, the values of the diagnostic parameters under consideration (X f. G-Q and Tjf.) Increase from 1 to 1.082 relative units.

The unevenness of the air gap is determined as follows.

With a uniform air gap disconnected from the mechanism of an induction motor with a phase-rotor (for example, after installation or overhaul), the temperature is measured.

five

environment, equal to the temperature of the motor windings, with a short-circuited rotor winding turn on the unloaded engine into the network positive acceleration. The current values in the phase windings of the rotor are measured, and the modulus of the current vector is determined. After reducing the current to a value of 0.5 1p. determine the time constant of its decrease.

The results of measuring the constant decay time of the current in the rotor, the temperature of the rotor winding of the engine before starting, and the frequency of rotation of the rotor at the time of disconnection from the network, which determines the overheating of the rotor winding during the start, are used as basic data

When controlling the air gap. 5, the same magnitudes are measured as in the baseline. The largest ratio of the air gap of the rotor in the bore of the stator of the engine, determined by periodic control of a constant time, reduced to the temperature of the baseline experiment, to the baseline value of this quantity, by the performance characteristic, determines

The predicted method of indirect control of the unevenness of the air gap51 of an asynchronous motor has increased accuracy and reduced labor costs.

0

0

five

Claims (1)

Invention Formula The method of indirect control of the unevenness of the air gap of an induction motor, which consists in measuring the temperature of the rotor winding, in short-term connection of the motor to the network, in measuring the rotational speed of the rotor, disconnecting the engine from the network, measuring the temperature of its windings, measuring the constant attenuation time of the diagnostic parameter , while the degree of non-uniformity of the gap is judged by the resistance of the constant decay time of the specified parameter and the temperature of the rotor winding with the base and mi with a uniform air gap, different 513270246 In order to increase the exact winding of the rotor, its frequency is measured, the control and reduction of the labor by which the rotational speed is determined for asynchronous engines from the engine's win and the time constant of the phase rotor, as a diagnostic attenuation current amplitudes at the disconnecting parameter use the current in the motor cues from the mains.