Slot harmonics in cage motors due to saturation of a main magnetic circuit

Abstract

Purpose

To study effects in the Fourier spectra of cage motor phase currents due to saturation of the main magnetic circuit by the fundamental MMF harmonic.

Design/methodology/approach

An idea of an equivalent magnetizing current is applied, which allows to consider an influence of all currents of stator and rotor windings on the main magnetic circuit permeability. The energy base approach is used to write machine equations and the harmonic balance method is used to determine the Fourier spectra of currents.

Findings

It has been shown that the saturation generate additional harmonics in phase currents, which are shifted by 100 Hz from the so called slot harmonics.

Research limitations/implications

A model and a solving method allows to predict all slot harmonics quantitatively, but qualitative difference of the Fourier spectra to measurement still exist.

Practical implications

More precise prediction of the Fourier spectra of stator phase currents for on‐line diagnostic systems.

Originality/value

A circuit model of a cage motor accounting for saturation by slot harmonics and an algorithm for determination of additional components in the phase current Fourier spectra.

Citation

Sobczyk, T., Weinreb, K., Sułowicz, M., Węgiel, T. and Warzecha, A. (2006), "Slot harmonics in cage motors due to saturation of a main magnetic circuit", COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, Vol. 25 No. 1, pp. 128-139. https://doi.org/10.1108/03321640610634399