Method for Determining the Degree of Damage to the Stator Windings of an Induction Electric Motor with an Asymmetric Power System

Abstract

A method is proposed for determining the number of damaged stator windings in the presence of an asymmetric power supply system for an induction electric motor based on the Park vector hodograph. As a result of the experiments on the simulation model, it was found that with the symmetry of the system of supply voltages and stator windings, the hodograph of the Park vector describes a circle; in all other cases it is an ellipse. It has been established that the presence of asymmetry in the supply voltage system is indicated by the angle of inclination of the ellipse, and the indicator of the presence of the asymmetry of the stator windings is the angle of ellipticity. In order to identify the presence of asymmetry of the stator windings in the conditions of asymmetry of the supply voltage system, an algorithm for recalculating the ellipse parameters for the condition of the symmetry of the supply voltage system was proposed. Recalculation errors did not exceed 6%. It has been established that the dependence of the increment of the amplitudes of the phase and angles of the phase currents of the stator on the number of damaged turns of the stator winding is linear. Based on this fact, an algorithm for determining the number of damaged turns was proposed. The results of this work can be used to build systems for diagnosing the interturn short circuit of the stator of an induction electric motor built into the drive.

Structural diagram of the built-in diagnostic system for electric drives of vehicles

“…The described methodology does not allow obtaining the degree of closure and is more convenient for bench monitoring of the motor condition. The papers [32,34] show the effectiveness of applying the Park vector hodograph method related to current diagnostic methods for the same problems.…”

“…The phase currents of the stator of an induction motor from the three-phase coordinate system are converted to the moving two-phase dq-coordinate system in accordance with the expressions [34] {…”

“…The angle of ellipticity for an orthogonal-circular basis is equal to [34] ε = arctg I pmin I pmax .…”

“…After that, it is necessary to enumerate the values of the projections of the Park vector obtained in the orthogonal-circular basis to the orthogonal-elliptic one. Enumerations are made in accordance with the expressions [34] i…”

“…In the orthogonal-circular basis relative to the d axis, θ0=0. The amplitude values of the currents i'sd0 and i'sq0 are calculated by the formulas [34] { I′ sd0 = √ (Re(i ′ sd0 ))…”