Wireless Power Transfer Model Based Estimation of Rotor Current and Temperature for Inductive Electrically Excited Synchronous Machines

Inductive wireless power transfer (WPT) system rotor supply for electrically excited synchronous machines enables reduced maintenance requirements and increased power density due to better rotor integration compared to conventional slip rings and brushes. However, the control of the rotor current and monitoring of the rotor winding temperature is challenging as the rotor current and voltage are inaccessible. This paper introduces a rotor estimator based on a semi-analytical steady-state WPT model. The estimation only requires the measurement of the primary side high frequency AC current which is conducted with a FPGA unit. Verification with steady-state and dynamic measurements shows good agreement between measured and estimated current and temperatures and thus, closed-loop current control and temperature monitoring is made possible.