Advanced High-Power-Density Interior Permanent Magnet Motor for Traction Applications

TLDR

Electric drive systems are essential for advanced vehicle propulsion, yet they must remain economical in cost, weight, and size while meeting performance and reliability expectations. This paper presents the design, analysis, and testing of an advanced interior permanent‑magnet motor for FreedomCAR 2020, emphasizing its novel spoke‑structured rotor and thermal‑management tradeoffs. The motor is a 12‑slot/10‑pole interior‑PM machine with a segmented stator using fractional‑slot nonoverlapping concentrated windings and a spoke‑structured rotor, operating at ~1.2 kHz and 180 °C, with detailed loss and demagnetization analyses. Prototype testing confirms that the advanced rotor and thermal‑management schemes satisfy performance targets, revealing tradeoffs among the different cooling strategies.

Abstract

Electric drive systems, which include electric machines and power electronics, are a key enabling technology for advanced vehicle propulsion systems that reduce the petroleum dependence of the ground transportation sector. To have significant effect, electric drive technologies must be economical in terms of cost, weight, and size while meeting performance and reliability expectations. This paper will provide details of the design, analysis, and testing of an advanced interior permanent magnet (PM) machine that was developed to meet the FreedomCAR 2020 specifications. The 12-slot/10-pole machine has segmented stator structure equipped with fractional-slot nonoverlapping concentrated windings. The rotor has a novel spoke structure/assembly. Several prototypes with different thermal management schemes have been built and tested. This paper will cover the test results for all these prototypes and highlight the tradeoffs between the various schemes. Due to the high machine frequency (~1.2 kHz at the top speed), detailed analysis of various loss components and ways to reduce them will be presented. In addition, due to the high coolant inlet temperature and the fact that the machine is designed to continuously operate at 180 °C, detailed PM demagnetization analysis will be presented. The key novelty in this paper is the advanced rotor structure and the thermal management schemes.