Isolated on-board integrated charger (IOBIC) decreases the cost of electrical vehicles and ensures the galvanic isolation between battery and grid. In this paper, the variable flux reluctance machines (VFRMs) are researched to investigate the feasibility of multiplexing VFRMs as the transformer in IOBIC. To identify an optimal stator-rotor combination, the 6/4, 6/5, 6/7, and 6/8 configurations are examined. Specifically, the coupling coefficient and voltage transfer ratio between two arbitrary windings of VFRMs are calculated to assess the transfer characteristics of the multiplexed transformer. However, their transfer ratios are low, which is undesirable for a transformer. Thus, field winding is split to build a new winding that is tightly coupled with phase winding. The voltage transfer ratio is improved greatly when the new winding and phase winding are multiplexed as the two sides of the transformer.

Coupling coefficient, IOBIC, transfer characteristic, VFRM, voltage transfer ratio