Torque maximization in high-torque density multiphase drives based on induction motors

Nowadays, there is an increasing interest towards multi-phase motor drives, i.e. with a number of phases greater than three, especially for medium and high power applications such as naval and railway propulsion systems. It is known that multiphase motors offer the opportunity to increase the torque density by adding a third spatial harmonic in the magnetic field. In this paper the problem of maximizing the torque capability in multiphase drives based on induction motors by adding a third spatial harmonic in the air-gap field is investigated in depth. The analysis shows that not considering the inverter and motor current rating may lead to suboptimal motor performance. The validity of the theoretical analysis is verified by numerical simulations and experimental results.