抄録
Magnetic properties of motor cores are deteriorated due to residual stress occurred during manufacturing process. Therefore, it is necessary to reduce the residual stress in motor cores through stress-relied annealing. As a conventional method, electric furnaces have been used to anneal motor cores. However it takes a long annealing time and requires high running cost for annealing with electric furnaces. In order to improve this method, we have developed a new stress-relied annealing technique with the usage of a low frequency induction heating. This paper presents the effect of the stress-relied annealing on the magnetic properties of ring cores. The low frequency induction heating can be extended the skin depth of eddy currents and achieved uniform heating in annealing.
