Regarding high-speed permanent magnet machines (HSPMMs), there is a lack of complete and detailed design processes for main parameters under multiphysics constraints, which makes it difficult to obtain high-reliability designs for designers of HSPMMs. This paper presents a detailed and complete design process for the main parameters of an HSPMM under multiphysics constraints. Firstly, the initial sizes are obtained through electromagnetic and mechanical design theory. Then, the influence of design parameters on rotor stress is analyzed in detail, including PM material, rotor temperature, sleeve thickness, PM thickness and rotor diameter. Furthermore, the rotor dynamics have also been studied in detail, including the effects of bearing stiffness, impeller mass, rotor diameter, core length, and gyroscopic effect on critical speed. Afterwards, the comprehensive research on the electromagnetic filed and the loss characteristics is performed. The cooling system is designed and the thermal field is also studied in Ansys-Cfx. Besides—the coupled temperature-stress analysis is established considering the interaction between temperature and mechanical characteristics. Finally, a full-size HSPMM prototype has been fabricated and tested to validate the detailed multiphysics design process.

Brushless DC motor (BLDCM) has been widely used in drive systems and servo control because of its fast response, high power density and high efficiency and so on. It is usually driven by a hard-switching PWM inverter, which has low switching frequency, high switching loss, high electro magnetic interference (EMI) and acoustic noise, etc. To solve the drawbacks of the voltage source type hard switching inverter, many types of resonant DC link inverters have been widely studied. However, these inverters have such drawbacks as high voltage stress of the devices, delta modulation, threshold limit of inductor current or capacitor voltage and sophisticated control. This paper proposed a novel zero voltage transition parallel resonant DC link voltage source inverter (ZVT-PRDCL-VSI) for BLDCM drive systems. The inverter possess advantages of low switching power loss, low inductor power loss, small device voltage stress, simple control scheme and no unbalancing problem of neutral-point voltage. The operation principle and control scheme of the inverter are analyzed. The validity of the circuit is verified by simulation and experimental results.