Design and test of torque adjustment system of five-phase fault-tolerant permanent-magnet machine

Multiphase fault-tolerant machines have many advantages, such as low torque pulsation, high reliability, highpower transmission under low voltage and so on. Therefore, they are attracting more and more attention in recent research. As the phase number of the machine becomes larger, its control degree of freedom increases. It is necessary to extend the Clark transformation to realize the decoupling control of the machine. Generally, there is a certain amount of the third harmonic in the permanent magnet flux linkage, and more third harmonic will be included with particular consideration. Injecting the third harmonic in the phase current, it is able to cooperate with the third harmonic in the permanent magnet flux linkage to improve the output torque, and the magnetic saturation degree of the machine can be decreased. The design of the torque adjustment system of a five-phase fault-tolerant permanentmagnet machine is investigated in this paper. An optimal apportionment of the fundamental harmonic and the third harmonic in the phase current is proposed, which is aimed at the application when the amplitude of the phase current is confined. The effectiveness of the designed system has been verified by the experimental results.