Measurement of noise associated with model transformer cores

The performance of a transformer core may be considered in terms of power loss and by the noise generated by the core, both of which should be minimised. This paper discusses the setting up of a suitable system for evaluation of noise in a large model transformer core (500 kV A) and issues associated with noise measurement. The equivalent continuous sound pressure level (LAeq) was used as a measure of the A-weighted sound level and measurements were made in the range 16 Hz–25 kHz for various step lap core configurations. The selection of optimum sound insulation materials between core and ground support and for enclosing the transformer is essential for minimisation of background noise. Core clamping pressure must be optimised in order to minimise noise. The use of two laminations per layer instead of one leads to an increase in noise arising from the core. Provided care is taken in building the core, good reproducibility of results can be obtained for analysis.