General Analytical Model of Inductance Variation by EMF-canceling Coil for Inductive Power Transfer System

This paper presents an analytical model and a design criteria for additional windings to reduce electromagnetic field (EMF) generated from inductive power transfer (IPT) systems. In particular, the canceling windings are connected to the main windings with common-mode connection, differential-mode connection, or short-circuited connection. Parameter variation, which may degrade the system efficiency, occurs in the IPT system owing to the unwanted coupling between the main windings and the canceling windings. Therefore, the theoretical analysis of the IPT system considering the canceling windings is conducted to evaluate the effects of the EMF shielding methods on system parameter variation. The calculation results of the system parameters agree with the measurement results in the prototype of the four-winding IPT coils, the error is lower than 5%. The simulation results with a 1-kW prototype IPT system indicate that the magnetic flux density at the distance of 50 cm from the bottom of the receiving coils decreases by at most 41% with the differential-mode connection.