Effects of External Field Orientation on Permanent Magnet Demagnetization

This paper investigates how the orientation of the applied demagnetizing magnetomotive force (MMF) affects the demagnetization behavior of Nd-Fe-B magnets that are widely used for permanent-magnet synchronous machines (PMSMs). This paper designs and builds a customized test fixture that can produce a magnetic field with varying orientation and intensity to demagnetize magnet samples. A computer-controlled 2-D mapping device is used to record the flux density above the test samples. The measurement results are compared with the 3-D finite-element analysis simulations. The understanding and insights obtained from this paper will be used to improve the robustness of magnet design for high power density PMSMs with improved capability of withstanding demagnetization during overcurrent faults.