Investigation and simulation of fields in large salient-pole synchronous machines with skewed stator slots

This paper presents the results of an investigative study performed on a large salient-pole synchronous machine with skewed stator slots. The study was carried out to aid the understanding of the phenomena related to electromagnetic field distribution, rotor damper currents and pole face iron losses in machines with skewed stator slots and an armature winding design with a fractional number of stator slots per pole. A hydrogenerator was specially instrumented to measure the variation of magnetic fields along the axial length of the machine and the induced currents in the damper bars on the rotor poles. A computational model has been developed to predict the air-gap flux density, damper currents and rotor iron losses. Measured results are compared with those predicted by simulation.