Acoustic Modeling and Prediction of Ultrahigh-Speed Switched Reluctance Machines Based on Multiphysics Finite Element Analysis

High-speed switched reluctance machines (SRMs) have been a timely topic recently. However, for ultrahigh-speed SRMs over 100,000 rpm, the acoustic noise is a significant issue in many applications such as high speed spindles, compressors/ turbochargers, flywheels, and etc. In this article, a multiphysics acoustic modeling of ultrahigh-speed SRMs is presented based on finite element analysis (FEA). First, a three-dimensional electromagnetic FEA is conducted to calculate the radial force on the stator teeth. Then, a modal analysis and a harmonic response analysis are shown in the frequency domain to estimate the natural frequencies and vibration of the whole motor. An acoustic response analysis is done to estimate the sound pressure level (SPL) using the superposition of the surface vibration. To verify the model, experiments are done to measure and compare the natural frequencies and the SPL of a 4/2 ultrahigh-speed SRM at 100,000 rpm. The results show that the SPL of the motor is as high as 115 dB at 10 mm away from the motor, which matches the simulation result (113 dB) well. The impact of the bearing is proven to be negligible compared with the noise generated by the radial force. Finally, a parametric study example of using the proposed model to guide the design of SRMs has been conducted. It is shown that "hot dog" shaped motors have less noise than "pancake" shaped motors under the same motor volume, speed, and power.