Influence of Stress-Relief Annealing on Magnetic Properties of Motor Cores Using Induced Current Heating Method

Abstract

This paper presents the effect of stress-relief annealing on magnetic properties using an induced current heating(ICH) method in order to reduce the residual stress in the motor cores. The magnetic properties of a motor core annealed using the ICH method were first compared with those of a core annealed using a conventional electric furnace. When the hold time in each method was the same, the magnetic properties using the ICH method were improved over those using the EF method. The effects of varying the annealing temperature and time for the ICH process were then investigated. It was found that the values of the maximum permeability increased and the hys-teresis loss decreased with increasing annealing temperature and time. The total time of the stress-relief annealing could be achieved in a short period of about one hour.