Steady-State Flat-Pickup Loading Effects in Polyphase Inductive Power Transfer Systems

Polyphase inductive power transfer systems have been proposed as a method of increasing the tolerance of roadway-based vehicular systems to the lateral movement of pickups. However, the design of the power supply is challenging due to the changing nature of the load presented by mobile pickups. An inverter driving a traditional single-phase system must be designed with only the peak power in mind, as the reactive load of the pickups is essentially constant due to the relatively constrained pickup movement and will normally be compensated when the system is designed. This is not possible for an inverter driving a polyphase track, as the reactive load will vary with the lateral position of the pickup, just as a portion of the real load that must be supplied by each phase will also vary. This paper presents a simple but accurate method of determining the real and reactive load on each phase of the track as the pickup moves, allowing the inverter to be correctly designed with appropriate component ratings.