Optimal ratio of field to torque phases in multi-phase induction machines using special phase current waveforms

This paper presents a simple criterion to calculate the optimal ratio of field to torque phases in a concentrated winding multi-phase induction machine using special phase current waveforms. The method is validated through finite element analysis. It is shown that with higher stator phase numbers, up to 66 - 80 % of the rotor winding is active at a time as fewer field phases are utilised. An almost constant square like air gap flux density and rotor induced voltage waveforms are produced when using the special stator current waveforms.