Parasitic losses in modular permanent-magnet generators

The modular permanent-magnet machine exhibits several new forms of load and no-load loss which could lead to poor efficiency and unacceptable temperature rise if not taken into account in the design. Four such losses are identified. An analytical electromagnetic model of the modular machine and its structure is developed and used to predict the losses. A test rig using modules which are representative of a full scale machine has provided data which validates the model. Use of the model for a typical full-scale design with enlarged modules reveals that the losses can be made acceptably low without special measures to screen the leakage fields which cause the loss.