Calculation of no-load damper-winding loss in synchronous machines

THE NON-UNIFORM nature of the air-gap due to the presence of alternate teeth and slots on the stator of synchronous machines results in a non-uniform distribution of flux density at the surface of the rotor. These pulsations in the airgap induction produce pole-face loss. When a damper winding is present the pulsations link the damper bars producing circulating currents causing an additional loss which is designated by the term 4 no-load damper winding loss. The magnitude of this loss is found to vary from practically zero to as much as eight times the pole-face loss, or to as much as half of the total no-load core loss. A method now has been developed for calculating the no-load damper loss, based on theoretical considerations.