Triangular DQ Tx Coils of Wireless EV Chargers for Large Misalignment Tolerances

Abstract

Wireless charging of electric vehicles (EV) are inevitable for user convenience of EV charging when the EVs are parked in the charging stations. A new set of triangular DQ transmitting (Tx) coils for wireless EV chargers is newly proposed in this paper for large longitudinal, lateral, and diagonal displacement tolerances. The proposed coil set consists of two layers, i.e., D-Tx and Q-Tx, where each Tx layer has two triangular coils of the same magnetic polarity diagonally, facing each other to generate a more uniform coupling coefficient between Tx and Rx w.r.t. the misalignments. In practice, diagonal misalignment tolerance is an important design criterion to deliver load power to EV because the worst scenario of misalignment is when longitudinal and lateral misalignments occur at the same time, i.e., diagonal misalignment. To solve these misalignment issues, the DQ transmitters were optimally designed to obtain uniformed output voltage against wide range of the diagonal misalignment situations. A prototype of an inductive power transfer (IPT) system having the proposed triangular DQ Tx coils for 3.5 kW wireless EV chargers was fabricated and experimentally verified with a switching frequency of 85 kHz, which can satisfy J2954 WPT1 class in the society of automotive engineers (SAE). As a result, it is found that 8.62 of the diagonal misalignment tolerance γd has been achieved, and this value is superior to the other Tx coils. IEEE