Noise generated by model step lap core configurations of grain oriented electrical steel

Abstract Although it is important to reduce the power loss associated with transformer cores by use of electrical steel of the optimum grade, it is equally important to minimise the noise generated by the core. This paper discusses the effect of variations in the number of steps (3, 5, and 7) and the step overlap (2, 4, and 6 mm) on noise associated with model step lap cores of conventional, high permeability and ball unit domain refined high permeability grain oriented electrical steel. A-weighted sound pressure level noise measurements (LAeq) were made at various locations of the core over the frequency range 25–16,000 Hz. For all step lap cores investigated, the noise generated was dependent on the induction level, and on the number of steps and step overlap employed. The use of 3 step lap cores and step overlaps of 2 mm should be avoided, if low noise is to be achieved. There was very little difference between the noise emitted by the 5 and 7 step lap cores. Similar noise levels were noted for 27M0H material in the non-domain refined (NDR) and ball unit domain refined condition for a 5 step lap core with 6 mm step overlap.