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This letter proposes a simplified offline preanalysis method of fault severity for interturn short-circuit faults (ISCFs) in fault-tolerant permanent magnet synchronous machines (FTPMSMs). For fault diagnosis and fault-tolerant (FT) control, it is important to predict how much short-circuit current will be generated at various speeds, loads, shorted turns ratios, and fault resistances. However, predicting the short-circuit current usually needs to solve differential equations by closed-loop simulation or finite element analysis (FEA). To increase the efficiency of fault preanalysis, the proposed method provides a simple solution to quickly offline predict the amplitude of short-circuit current. Simulation and experimental results show the effectiveness of the proposed method for different fault severities and various operations.

Predictive position control (PPC) method with long predictive horizon is an effective method to eliminate the cascade structure and improve the dynamic response for the permanent magnet synchronous motor (PMSM). However, traditional PPC method needs a time-consuming prediction process and does not always guarantee satisfactory position performance. In this article, a simplified constrained PPC method is proposed, the Laguerre functions are designed to construct the control trajectory of position system, which offers two control degrees to improve the position dynamic response and simplify programming of prediction process. Besides that, the optimization model with current constraints, speed constraints, and voltage constraints are constructed with the frame of Laguerre functions. The optimization model with constraints is solved with an optimal method and suboptimal method. The proposed PPC method is experimentally verified and compared with field-oriented control (FOC) method and a traditional PPC method, the results have proved that proposed method has excellent position performance and low calculation burden.

The 150$^\circ$ mode 12-step control (150-TSC) is suitable for high-speed drives since it can generate a quasi-sinusoidal current waveform compared with the conventional 120$^\circ$ mode six-step control. However, for high-speed brushless direct current drives, the relatively large commutation angle of 150-TSC will cause a noticeable phase delay error. Additionally, the low switch-to-fundamental ratio will cause significant pulsewidth modulation (PWM) delay, which leads to large current oscillation and ripple. In this article, an asynchronous PWM scheme is proposed for 150-TSC to eliminate PWM delays. A phase delay error compensation method based on stator current is further proposed. The optimal phase advance angle is generated for minimum stator current magnitude with the help of the gradient descent optimization algorithm. A quasi-sinusoidal phase current can be achieved and the current harmonics can be reduced. The effectiveness of the proposed strategy is verified by experimental results.