Low-Voltage-Power-Supply-Fed 1.5-kW 150,000-r/min Ultra-High-Speed PM Motor Designed to Maximize Efficiency and Power Density

Abstract

This paper discusses a design approach for an ultra-high-speed permanent magnet (PM) motor whose specific application is an electrically operated supercharger for automotive engines. The motor is fed by a three-phase inverter with a 12-V battery power supply for automotive applications. The investigated motor has a rated output power of 1.5kW and a maximum rotation speed of 150,000r/min, and is designed to maximize both the efficiency and the power density. In order to achieve this goal, various technical problems must be overcome, e.g., the synchronous impedance must be greatly reduced, the iron and copper losses must be minimized, the power density must be improved, and mechanical stabilization in the high-speed operation range must be achieved. An electromagnetic field analysis on the basis of a finite element method (FEM) is conducted to fine-tune the detailed motor dimensions and to maximize the efficiency and power density at the same time. Consequently, the efficiency has been improved to over 97% (excluding mechanical losses), and the power density has been increased to approximately 13W/cm³ at the rated output power in the prototype motor design. The feasibility of the design is confirmed through experimental tests, using a prototype motor.