The Causes and Characteristics of Transformer Noise

This report gives the main results of an investigation made by the British Electrical and Allied Industries Research Association for the purpose of providing some fundamental information on transformer noise. The experimental work was carried out at University College, London, between 1935 and 1937. Harmonic analyses of the noise emitted by a series of model cores were made under accurately controlled conditions of core clamping, flux density, etc. It was concluded that the noise is due mainly to the effects of magnetostriction in the core and to local vibration of the stampings at the core joints. The results of an investigation of magnetostriction in transformer steel are used as the basis of an analysis of the core vibration, and some agreement between theoretical and experimental results is noted. The general properties of the noise are described. It is found that coil vibration can be responsible for small amounts of noise.