Noise and vibration characteristics of sub-fractional horsepower single-phase BLDC drives

Abstract

Single-phase brushless DC (BLDC) drives are a cost-effective alternative for three-phase sub-fractional horsepower drives in automotive auxiliary applications. Inherent features of single-phase permanent magnet machines, such as high cogging torque and torque ripple, can, however, make them more audible than their three-phase counterparts. As some of these auxiliary drives are close to the passengers, where even a small amount of noise can be disturbing, the investigation into noise sources is essential to further address this challenge. In this paper, the dominant noise and vibration characteristics of single-phase BLDC machines are investigated for two different stator structures, i.e., salient-pole and claw-pole, and compared. Magnetic force density waves and finite element (FE) analyses are performed to analyze the electromagnetic forces resulting from the open-circuit condition as well as different switching strategies in the load condition. Structural analyses show that due to the mechanical structure’s lower stiffness and natural frequencies in the audible range, the example case machine with the claw-pole stator develops higher structure- and air-borne noise than the machine with the salient-pole stator.