Performance Assessment of More Electric Aircraft Drive Motor Insulation

The electrification of aircraft is a worldwide craze. Inverter-fed motors are a vital component of the future more electric aircraft (MEA) propulsion system. However, designing reliable inverter-fed motor insulation systems for MEA is challenging due to the low pressures at the cruising altitude of MEA. Considering the extremely high reliability requirements of MEA, any minor defect in the insulation system would be a potential threat to the safe operation of the aircraft. Therefore, it is essential to investigate the potential insulation risks in the current inverter-fed motors manufacturing process, which are often overlooked. This paper mainly investigates the manufacturing processes including: film-wrapping for enamelled round wires, impregnation and potting for stators. Firstly, partial discharge inception voltage (PDIV) tests were performed on enamelled-wrapped round wires. Experimental results on enamelled wires with 30 µm thickness polyimide (PI) show that, although the PDIV of the wrapped enamelled round wires with 30 µs thickness PI film can be increased from around 1.6 kV to 3.0 kV, the wrapped round wires should be carefully used as the wrapped films used are susceptible to wrinkling during the manufacturing process. Secondly, the impregnation process on random wound and hairpin stators was investigated. It was found that (1) the PDIV performance of the main insulation of both random wound and hair-pin stators is largely dependent on the impregnation process (2) all air bubbles are impossible to remove by both trickle impregnation and vacuum pressure impregnation (VPI) process (3) the stators random wound and hair-pin stators have the lowest PDIV values at 200 Pa and 750 Pa, respectively. Moreover, the feasibility of the potting process on stator electrical insulation systems was investigated by PDIV test results at different air pressures. Test results performed on stator insulation systems show that the influence of air pressure on the PDIV values is neglectable after the potting process. The results reported in this study are expected to provide experimental support for the insulation design of drive motors used for MEAs.