Interturn fault tolerant drive method by limiting copper loss of interior permanent magnet synchronous motor

An interturn short fault (ITF) is a common failure in electrical machines because the windings easily lose insulation characteristics due to overheating and mechanical stress. In the ITF winding, large fault current, ohmic loss, and excess winding heat are induced, resulting in fault aggravation and combustion of the machine unless adequate fault diagnosis and management are undertaken. By limiting the overall copper loss, including the component due to the ITF, the faulty motor can operate without aggravation until adequate fault management actions can be performed. In this article, an interior permanent magnet synchronous motor (IPMSM) ITF tolerant drive method by limiting internal copper loss is proposed. The copper loss by the ITF is simplified in the proposed method and analyzed for various current, speed, and output torque conditions. By maximizing the output torque with minimum IPMSM copper losses, the maximum torque per loss (MTPL) operation point is suggested. Compared to the maximum torque per ampere, the MTPL has a more efficient operation point with ITF. To verify the proposed method, experimental studies are performed with an IPMSM having ITFs. The results show the feasibility and practicality of the proposed method.