High-Torque-Density Control of Multiphase Induction Motor Drives Operating Over a Wide Speed Range

The high-order harmonics of the magnetic field can be used in some typologies of multiphase machine to improve the torque density. However, maximizing the torque capability depends on the thermal, voltage, and current constraints of the machine and the inverter. In this paper, a rotor-flux-oriented control scheme, which is capable of exploiting the maximum torque at any speed, is presented for multiphase induction motor drives. Below the base speed, the torque improvement is obtained by adding a third harmonic component to the fundamental component of the air-gap magnetic field. At high speeds, the amplitude of the field harmonics is progressively reduced to ensure the widest possible operating speed range. The validity of the proposed control scheme is confirmed by experimental tests.