Effect of residual stress on magnetic properties of motor cores

The magnetic properties of electrical steel sheet deteriorates due to residual stress, which occurs during the manufacturing process. Therefore, it is important to know the relationship between the magnetic property and the residual stress in order to utilize electrical steel sheets effectively. This paper presents the effect of residual stress on the magnetic properties of motor cores in a rotating machine. First, the local residual stress distribution of the motor core is measured using an X-ray stress measurement system. Next, the magnetic properties of the motor cores for the different residual stress distributions are measured using a single sheet tester. Based on these results, the maximum permeability and magnetic power loss differed depending on the sample, each of which had a different residual stress. In addition, we attempt to measure the inductance of the motor core in order to easily evaluate the magnetic property. The difference in the inductance of each sample was obtained based on the excitation voltage and frequency measured using an LCR meter. It is very useful to evaluate the inductance in order to easily determinine the difference in the residual stress.