Power Transfer Capability and Bifurcation Phenomena of Loosely Coupled Inductive Power Transfer Systems

TLDR

Loosely coupled inductive power transfer (LCIPT) systems are designed to deliver power efficiently from a stationary primary source to one or more movable secondary loads over relatively large air gaps via magnetic coupling. The paper presents a general approach to identify power transfer capability and bifurcation phenomena in LCIPT systems. A high‑order mathematical model of primary and secondary resonant circuits is employed, with primary compensation tuned to match the zero‑phase‑angle frequency to the secondary resonance for maximum power and minimal VA rating. Validation with a contactless EV battery charger confirmed the theory, and following the proposed bifurcation criteria guarantees bifurcation‑free operation while controllable operation within the bifurcation region can yield a significant power increase.

Abstract

Loosely coupled inductive power transfer (LCIPT) systems are designed to deliver power efficiently from a stationary primary source to one or more movable secondary loads over relatively large air gaps via magnetic coupling. In this paper, a general approach is presented to identify the power transfer capability and bifurcation phenomena (multiple operating modes) for such systems. This is achieved using a high order mathematical model consisting of both primary and secondary resonant circuits. The primary compensation is deliberately designed to make the primary zero phase angle frequency equal the secondary resonant frequency to achieve maximum power with minimum VA rating of the supply. A contactless electric vehicle battery charger was used to validate the theory by comparing the measured and calculated operational frequency and power transfer. For bifurcation-free operation, the power transfer capability and controllability are assured by following the proposed bifurcation criteria. Where controllable operation within the bifurcation region is achievable, a significant increase in power is possible.