The paper investigates the effect of the bar number on the performances of a five-phase squirrel-cage induction machine with fractional-slot tooth concentrated winding. With a same stator, five different rotor bar numbers are chosen and the rotor magnetic circuits are designed using an analytical approach. Then, a finite-element analysis is done under two different supply conditions: fundamental currents and third harmonic currents. Finally regarding the used winding specificities the possibility of second harmonic current supply is evaluated. The results are presented in a comparative way in order to determine the impact of rotor bar number on torque quality for the different supply modes.

Multiphase induction machines have the advantage of producing torque under different current harmonics. Theoretically, with some simplifications, the maximum produced torque can be considered proportional to the harmonic winding factor related to the injected current harmonic. However previous work has shown that this theoretical proportionality between the maximum developed torque and harmonic winding factors is not obtained in the case of a five-phase induction machine with eight-poles and fractional-slot tooth concentrated winding. This paper aims to investigate the effect of winding parameters, especially phase number, fundamental polarity and stator slots number, on the torque production in multiphase induction machine under harmonics injection. A comparative study is done between four five-phase winding configurations, with the same geometry and copper volume, under both first and third harmonic injection. Finally, a special 15-phase winding presenting better consistency between maximum developed torque and harmonic winding factors is proposed.

For three-phase induction machines supplied by sinusoidal current, it is usual to model the n-bar squirrel-cage by an equivalent two-phase circuit. For a multiphase induction machine which can be supplied with different harmonics of current, the reduced-order model of the rotor must be more carefully chosen in order to predict the pulsations of torque. The proposed analysis allows to avoid a wrong design with non-sinusoidal magnetomotive forces. An analytical approach is proposed and confirmed by Finite-Element modelling at first for a three-phase induction machine and secondly for a five-phase induction machine.