Abstract：Permanent magnet synchronous motors (PMSMs) are widely used in aerospace and electrified transportation due to their high efficiency and simple structure. However, faults such as open-circuit, short-circuit, and inter-turn short-circuit may occur in practical operations due to different operating conditions, which is big challenge forthe safety of applications. Therefore, a detailed 2D electromagnetic model and a 3D fluid-solid-thermal coupling model are established to investigate the temperature distribution of the target motor before and after an inter-turn short-circuit fault.This article provides a basis for further study of preventing inter-turn short circuit fault. In this paper, a fault-tolerant multiple 3-phase permanent magnet synchronous reluctance machine (PM-SynRM) with 18 slots, 14 polesand concentrated winding is selected as the study object. First, the target motor and its winding were modelled. Assuming that the fault occurred in the A1 coil, the phase A winding was divided into the healthy coil AH, the faulty coil AF, and the healthy coil A2. Then, the Ansys-Fluent software was used to construct a fluid-solid-thermal coupling simulation model in which the eight-turn coils were modelled individually. In the model, a large air domain was applied to simulate the natural cooling processin order to reduce the calculation error. The simulation was set to operate at 2 000 r/min with a load of 67 A to obtain the machine temperature distribution before the short-circuit fault. The overall temperature of the motor gradually decreased from the middle to the end, and the winding temperature decreased radially toward the motor shell. Then, the motor with an inter-turn short-circuit fault at the end was simulated to obtain the temperature distribution. The results showed that the established model is an effective toolto investigate the temperature distribution of the motor before and after an inter-turn short-circuit fault. Then, the factors affecting the temperature rise due to inter-turn short-circuit were analyzed. Different simulation scenarios were conducted for short-circuit coils consideringfour aspects: position of the short-circuit coil, number of short-circuit turns, load current and operation speed.It is found that the coil at position 1 on the outermost layer was the most severely affected when a single-turn fault occurred, and the temperature was peaked at 165℃. The short-circuit current and the temperature decreased with the number of short-circuited turns increasing and the load current and speed reducing.Finally, an experimental platform was built using a 5 kW 9-phase PMSM and the most severe single-turn fault was selected for testing.The motor temperature before and after the fault happened under rated load conditions were measured. Furthermore, the temperature with a load current of 40 A after fault was measuredin order to confirm the factors affecting the temperature rise of inter-turn short circuit. The experimental results verified the correctness of the simulation model. According to the investigation, the following conclusions can be drawn: (1) A 3D finite element fluid-solid-thermal coupling model is established which can accurately predict the temperature rise of the motor before and after a turn fault, and the highest temperature of the motor is usually located at the end winding. (2) Detailed winding modeling is helpful for investigating the temperature rise due to inter-turn short-circuit faults, and the temperature is affected by the position and number of short-circuited turns, with the single-layer coil located at the slot opening being the most severely affected. (3) As the load and speed increase, both the short-circuit current of the motor and the temperature increase.(4) Terminal short-circuit can effectively suppress the inter-turn short-circuit current and achieve good fault-tolerant effect.
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2023, Vol. 38 
