Analysis and Experimental Verification of a Conventional Inverter With Output LC Filter to Drive Ironless Stator Axial-Flux PM Motor

Ironless stator axial-flux permanent magnet (PM) machines are becoming a promising choice in aerospace and automotive applications. However, they come with the characteristic of extremely small armature inductance, which will result in a challenging difficulty to drive with the conventional inverter. Considering the limitation on increasing the switching frequency of high-power devices, a practical and cost-effective power circuit for driving an axial-flux ironless stator PM motor is developed for the application with high dc-link voltage, high-power level, and high fundamental frequency. A new and simple control strategy of the inverter with output inductor-capacitor (LC) filter is studied to achieve a well steady and dynamic performance for driving ironless stator PM motors. The dual closed loop of the phase current of the motor and the branch current of capacitors ensures the stability and torque control of the system. Due to the dual-loop current regulator, the maximum torque per ampere control is achieved. Meanwhile, the sinusoidal current with low harmonic content injected into the armature winding is of great significance for improving the performance of ironless stator AFPM motor. It proves that the development of the power circuit topology and effective control method provides an available solution for ironless stator motors or high-speed motors with small inductance.