Crosstalk of DQ Dipole Coils in Omnidirectional IPT

A phenomenon called “DQ crosstalk” has been discovered in inductive power transfer (IPT) systems that uses a crossed DQ dipole coil for omnidirectional wireless power transfer. Crosstalk refers to nonlinear magnetic interaction between D and Q coils of a DQ dipole coil, in which the current in one coil is affected by the other coil. The crosstalk is investigated in this article and the reason for it is turned out to be magnetic saturation at the intersection part of a DQ coil. Mutual inductance between D and Q coils, which can be minimized for a well-made crossed DQ coil, is identified to be not the major reason for the crosstalk. As one of the D and Q coils is saturated, the inductance of another coil is reduced through the intersection part. Then, the LC resonant frequency of the D or Q coil and its compensation capacitor increases, which results in higher current that eventually leads to saturation. In this way, saturation of one coil stimulates saturation of another coil, and vice versa. When a crossed DQ coil enters to partial saturation, which is inevitable for maximum power delivery in many practical applications, the IPT system can be eventually collapsed due to positive feedback of saturation. The mechanism of DQ coil saturation considering crosstalk is identified and simulated by a finite element method. An experimental prototype of a DQ coil with a test circuit at 9.4 kHz verified the crosstalk phenomenon by evaluating the distortion of one coil current when the other coil is saturated. Crosstalk effects such as inductance variation, phase mismatch, and core temperature increase on an IPT system at 198 kHz were also verified, and remedies for the crosstalk are suggested.