Measurement of Stator Core Magnetic Degradation During the Manufacturing Process

A quick and simple test method for measuring the B-H curve and power loss in generator stators, both as loose laminations and finished core packs, has been developed. This provides a greater level of understanding about the characteristics of stator cores at various stages of the manufacturing process in order to prevent finished generators from being out of specification. The capabilities of the measurement rig have been explored both theoretically and experimentally. Experiments have been carried out on-site on industrially manufactured synchronous generators, and permeability and power loss in a batch sample of stators have been measured. Considerable degradation in the steel´s magnetic properties has been found. The mean permeability at 1 T decreased by 23% after compression and welding. For specific power loss, the welding process caused an increase of 5% in the mean value and an increase of 36% in the standard deviation. The results allow conclusions to be drawn regarding manufacturing effects, variability, and generator performance.