Optimized handling of permanent magnets within the mass production of electric traction drives

The intention of this paper is to describe the magnetization process of NdFeB-magnets in the series production of electric traction drives using different approaches. Therefore it was verified if magnets assembled in a rotor can be fully magnetized with a magnetizing device. In addition it was studied if the individual magnets can be de-magnetized using various methods and can be re-magnetized again. Two rotors were assembled with non-magnetized magnets, and were magnetized with a special magnetization fixture. To check the quality of this magnetization process, one rotor with manufacturer magnetized magnets was assembled, which serves as a comparative. All rotors were verified with a flux coil, which is built in the magnetization fixture. The rotors then were assembled using the same stator to become an electric machine. The back EMF and the speed-torque characteristics of this machine were measured on a test bench. After these tests, the magnets were removed from the rotors, measured with the Helmholtz coil. The results show that the magnetization process of in the rotor magnetized magnets provides a satisfactory result.