Novel Direct Field and Direct Torque Control of Six-Phase Induction Machine with Special Phase Current Waveform

In this paper a novel direct field and direct torque control of a six-phase induction machine with special phase current waveform is proposed and evaluated. With the special current waveform a nearly square, smooth rotating flux density in the air gap is generated. The dominant merit of the proposed control and special current waveform is that the flux and torque of the induction machine are directly controlled as compared to vector control that uses transformation theory. Theoretical and finite element analysis is used to calculate amongst other things the torque and MMF balance control constant of the drive. A six-phase induction machine drive system is developed to evaluate the performance of the proposed control scheme. The steady state experimental results show good agreement with calculated results. The measured torque response shows that the proposed drive system has good dynamic performance.