This paper focuses on the loss estimation for the multiphase induction machine (IM) operating under fault-tolerant conditions through the field–circuit coupling finite element method (FEM). Both one-phase and two-phase open-circuit faults of a seven-phase IM are researched, and different spatial positions of the fault phases are taken into consideration. The magnitudes and phase angles of the residual phase’s current are deduced based on the principle of equal magnitude of the residual phase currents and unchanged fundamental magnetic motive force (MMF). The magnetic fields’ coupling between the fundamental and harmonic planes is analyzed. Then, the time-stepping electromagnetic fields calculation of the seven-phase IM are carried out under the commercial software Simplorer–Maxwell environment. The transient and steady performance for both the health and fault conditions are obtained based on the rotor field-oriented control (RFOC) strategy. The Joule loss and iron loss are calculated for the torque step and slope responses. The seven-phase motor driving platform is established to verify the numerical calculation results. The proposed method is effective for predicting the loss and designing a reasonable operating range for multiphase IM operating under fault-tolerant conditions considering the thermal balance.
The multiphase induction motor (MIM) suffers the problems of unsmoothness and slow dynamic response during the process of electronic pole-changing. To solve this issue, a cosine-response strategy based on proportional resonance (PR) current controller is proposed. Firstly, a current switching strategy with cosine-response is designed, which makes the MIM work more smoothly while switching between two planes. Then, the PR controller based on static coordinate system is adopted to replace the traditional proportional integral current loop controller, which realizes the zero steady-state error tracking of the current and improves MIM's dynamic response. Experiments on a five-phase induction motor verify that the proposed strategy can reduce the fluctuations of the torque, speed, and total harmonic distortion of phase current. Besides, it can improve the dynamic response of the torque and speed when the pole-changing is switched.
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