A method for establishing a wind turbine generator with one or more Permanent Magnet (PM) rotors. The method comprises the steps of: manufacturing a generator prepared for taking one or more PM rotors, manufacturing one or more rotors comprising a plurality of holding means prepared for retaining PM material, mounting substantially non-magnetized PM material prepared for magnetization in said holding means before or after said one or more rotors are mounted in said generator, connecting a magnetization system for magnetizing said PM material in the generator, and magnetizing said PM material with said magnetization system. The invention also relates to a wind turbine nacelle, a wind turbine comprising said wind turbine nacelle and use of a wind turbine.