Noise and Vibration Analysis of Zero Rare-Earth Magnet Integrated Starter-Generator for Military Vehicle Applications

Most hybrid electric vehicle (HEV) applications require the utilization of electric motors that have high torque/power density, high efficiency, a wide speed range and reliability. Interior permanent magnet (IPM) synchronous motors comprised of rare-earth magnet material is the most common electric motor class used for HEVs. However, recent fluctuations in the rare-earth magnet pricing and availability demands the search for zero rare-earth motor topologies as an alternative to IPM for use in HEVs. Switched reluctance machines (SRMs) are rare-earth free alternatives with simple and very robust construction, high efficiency/reliability, high torque at low speed, more thermal capability, and a wide constant power region. Nonetheless, they have several disadvantages which emerge from the nature of the torque production in SRMs, such as high torque ripple, high vibration, and substantial acoustic noise. This paper investigates the acoustic noise mitigation techniques of SRMs with Finite Element Analysis and experimental verifications.