Different from the traditional transformer，a new type of rotary transformer which has a rotary secondary winding was proposed to replace the brushes and slip rings of double-fed induction machines. The rotary state makes the no-load loss and temperature distribution of the transformer have complex characteristics which could not be calculated by the traditional loss formula. In this paper, based on the electric -thermal coupling theory, the actual thermal distribution model of rotary transformer was analyzed and the equivalent no-load loss calculation method was applied to the thermal field. Compared with other methods, the new method has higher calculation accuracy, which can be used in practical engineering. The correctness and validity of the no-load loss calculation are verified by simulation experiment.

Rotary Transformer;No-load Loss;Thermal Field;Electric-thermal Coupling