The paper deals with the main effects occurring in the phase currents of cage induction motor with rotor and stator core anisotropy. Searching for the currents spectrum components was conducted basing on the form of magnetic field energy function. The nonlinear function approximating main field energy versus magnetising flux linkage consist of all windings main flux linkages. The leakage fluxes of winding were omitted because the research has been limited to the motor free running only. The specified current frequency components were sought in the measurement current spectra of tested double-cage motor. The positive and negative symmetrical components of frequency components being multiplication of supplied frequency are produced by the stator core anisotropy. The frequency components dependent on rotor slip are generated by the rotor core anisotropy. Presented results may be useful in the diagnostic of induction motors.