Air-Gap-Insensitive IPT Pad With Ferromagnetic and Conductive Plates

A new conductive-plate-integrated inductive power transfer (IPT) system for automated guided vehicles with little output power variation according to air-gap changes between the transmitter (Tx) and receiver (Rx) is proposed. The inductance change of the ferrite core due to variations in the air gap is nullified by a corresponding change in an aluminum plate. Compared to conventional ferrite IPT systems, self-inductance of the proposed Tx coil is little changed against air-gap variations, which results in robust resonant frequency and output voltage. The self-inductance was experimentally verified to remain within 0.45% even when the air gap changes by fivefold from 10 to 50 mm. The output power variation became a twelfth of that of the conventional ferrite IPT for air-gap variations of 30 ∼ 50 mm, where the efficiency was found to be 96.0% when the output power was 1 kW.