Field Calculations of an Induction Cage Motor Taking into Account Magnetic Core Anisotropy

Magnetic core anisotropy of induction motors can disturb control processes or diagnostic procedures. This paper presents the level of secondary mechanical and electrical effects generated by an anisotropic magnetic core of two-pole cage motor. 2D field calculations were used to determine the magnetic field co-energy and the fluxes linked with three phase winding supplied with three phase current sources. The model used for calculating the main field had the rotor without any cage bars. The reduced field model for calculating the stator leakage field included the stator core and the rotor core teeth only. Waveforms of the magnetic field co-energy allowed to determine the harmonics components of the electromagnetic torque. The waveforms of the phase fluxes were the basis for determining the spectra of the phase voltages symmetrical components in an idle run and in a start-up state. The frequency levels components due to the rotor core anisotropy are shown. According to the reciprocity theorem the analogous spectra should be predicted in the currents when motor is supplied with the voltage sources.