Open-Phase Fault-Tolerant Pole Transition Control of an Asynchronous Variable-Pole Machine Using Harmonic Plane Decomposition

Automotive applications are revisiting the use of induction machines as magnet-free propulsive solutions due to their intrinsic robustness and reliability. Special multiphase configurations are under investigation to reduce the losses further and fulfill the stringent energy-efficiency and compactness requirements of the automotive industry. One of these configurations is known as variable-pole machines, which allows the number of magnetic pole pairs to change on the fly. These machines can stretch the torque-speed operating region, exploit the maximum torque capability, and exhibit competitive efficiency. Although fault tolerance has been widely explored for multiphase machines, the same cannot be said for variable-pole machines because, until recently, complete models to describe their dynamics under any condition, including magnetic pole changing and fault occurrences, were unavailable. This paper presents a post-fault control strategy for variable-pole machines with an open-phase fault, which can operate during pole changing and addresses the issue of fault-tolerant operation. The effectiveness of the control system is verified by experimental tests carried out with an eighteen-phase variable-pole induction machine prototype.