Highly Integrated Wireless Power Transfer System for an Inductive Electrically Excited Synchronous Machine

In this paper a highly integrated wireless power transfer system intended to replace the slip rings of an electrically excited synchronous machine is proposed. The loosely coupled ferrite-less rotary transformer as well as the secondary side power electronics are placed into the rotor hollow shaft of the machine. In addition to the compact construction, the design also focuses on enhancements in efficiency, mechanical stability and the cooling of the WPT system. Moreover, the use of a hollow shaft made out of glass fiber reinforced plastic reduces the necessary installation space significantly. The laboratory measurements demonstrate that in an installation space of less than 0.3 l a power of 2.5 kW is transmitted with a peak efficiency of 95 % at a frequency of 350 kHz.