Analysis and Test Results of a Brushless Doubly Fed Induction Machine With Rotary Transformer

This paper analyzes a 90-kW brushless doubly fed three-phase induction machine in which a wound rotor circuit is connected to a rotary transformer. It presents the advantages of substituting brushes and slip rings by a rotary transformer. In addition, it shows the rotary transformer design and presents the doubly fed induction machine operation. The steady-state model considers electrical circuit techniques to provide information about current, power factor, and efficiency on load. Equivalent circuit parameters are obtained through laboratory tests under a prototype. Comparisons between simulation and measurement results attest the good performance of the adopted model.