Post-assembly magnetization of rare-earth fractional-slot permanent-magnet machines using a Two-Shot Method

This paper studies the post-assembly magnetization of a fractional-slot brushless rare-earth surface permanent-magnet machine with six rotor poles and nine stator slots. In the paper, the simulation method is discussed and it is illustrated that it is possible to fully magnetize the machine after assembly using two pulses of the winding (“Two-Shot Method”) with a rotation of the rotor between pulses. The MMF required for this process is predicted. The method is then validated experimentally using a test motor and a magnetizer. The machine can be magnetized using connection of either two phases or three phases and both scenarios are investigated. The open-circuit back-EMFs are obtained to illustrate the partial magnetization after one pulse and full magnetization after two pulses. With the increasing use and size of rare-earth magnet machines the magnetizing procedure is an important aspect of their manufacture; pre-magnetized assembly can be difficult.