Noise and vibration reduction for IPMSM by using rotor circumferential slits

In this paper, rotor slits on the rotor's outer circumference is adopted to reduce certain harmonic components of radial forces and, hence, acoustic noise and vibration in an interior permanent magnet synchronous machine (IPMSM). The 48th order of harmonic component for the radial force is found to be responsible for the noise and vibration problem in the studied motor. For this purpose, the influential natural frequencies, speed range, and order of harmonic components for radial force are analyzed in a systematic way. A set of design procedures is formulated to find the proper locations for the slits circumferentially. Two base designs have been identified in electromagnetic analysis to reduce the radial force component and, hence, vibration. The features for both base models are combined to create a hybridized model. Then, the operating conditions, such as speed, current, and excitation angle are investigated on the hybridized model, in the high-dimensional analysis. At influential speed region, the hybridized model achieved up to 70% drop of 48th order harmonic for radial force in a wide operating range, and the highest drop goes up to 82.5%. Torque drop in the influential speed ranges from 2.5% to 5%.