Stray-Load Losses in Yoke-Beams of Transformers

Abstract

The yoke-beams, serving for clamping the yoke of the transformer core and for supporting the windings, are structural parts of complicated shape. The beams are in the stray magnetic field of the windings and the stray flux can produce considerable eddy current losses in them. Due to the large surface and efficient cooling of the beam hot spots generally do not form, however, the loss can reach or even exceed the tank losses. Thus it is advisable to assess the stray losses in the yoke-beams as well when designing the transformer. However, it is impracticable to accurately simulate such a complicated construction in the calculation and to pay attention to the non-linearity as well as the reaction of induced eddy currents at the same time. Calculation methods based on simplified models and on simplifying conditions are required. In the following two simple models are presented for the approximate calculation of the losses in yoke-beams. The losses calculated are compared to those measured on a transformer.