Loss Reduction in a Salient Pole Synchronous Machine Due to Magnetic Slot Wedge and Semiclosed Stator Slots

Influence of the magnetic slot wedge and semiclosed stator slot is studied. The study focuses on the air-gap flux density fluctuation due to the permeance harmonics and associated rotor losses of the machine. Both, the no-load and nominal load simulations are performed for the geometry with non-magnetic slot wedge, with ferrite based magnetic slot wedge and semi-closed slot geometry. The semi-closed stator slot geometry in the field wounded synchronous machine has remarkable influence to reduce the permeance harmonics and as a consequence, the rotor surface and damper bar (DB) losses of the machine. The air-gap length is studied to minimize the total loss of the machine. Variation of the rotor core, damper bar and field winding losses and root causes of these variations are investigated. The study is performed by 2D time discretized finite-element analysis (FEA).