Performance estimation and thermal analysis of permanent magnet brushless dc motor under corroded magnet condition

Abstract

The aim of this research is to analyze the permanent magnet Brushless Direct Current (BLDC) motor used for Electric vehicle application under corroded magnet condition. In this research both inner and outer rotor topologies of the BLDC motor have been taken for investigation. The thermal behavior and the dynamic performance of the inner and outer rotor BLDC motor with corroded magnets are considered. In high speed application of EV, the conventional or Shafted (inner rotor) BLDC are motors widely used with transaxles. BLDC motor and Transaxle are mechanically coupled with fixed gear ratios.This high speed low torque motors are very sensitive to change in speed. Very small changes in speed will impact the wheel rotation of the vehicle. Meantime, the outer rotor BLDC motors are used in Low speed High torque application with high torque capability. The magnets used in BLDC motors are unique and strong enough to support the Electric vehicle propulsion. Under open environment, the corrosion can be easily occurred in magnets and the corrosion around the magnets highly influences the speed and torque capability of the motor because of diluted flux density. Permanent magnets are the natural resources and they are more vulnerable to the same nature, specifically to moisture and water. In this research, a detailed investigation of BLDC motors with corroded magnets has been carried out. Each component contributing power loss has been analyzed to estimate the losses occurred in this motor. Due to corrosion, the effective magnet length (thickness) has been reduced towards the magnetizing direction. This reduction directly impacts the flux density concentration, because of change in physical dimension of the magnet and airgap. newline