2-D Thin Coil Designs of IPT for Wireless Charging of Automated Guided Vehicles

Abstract

As the automated guided vehicles (AGVs) play an important role in automated logistics systems, the wireless power transfer (WPT) technologies become a viable solution to provide the AGV with the automatic power charging service. In order to install the WPT systems to the small confined space in the AGV, a 2-D thin coil design is necessary for the receiver (Rx) system installed in the AGV. To greatly reduce the thickness of the Rx coil, including resonant capacitors, an ac/dc rectifier, and dc-link capacitors, an 2-D coil design for a minimum core loss is newly proposed in this article. Based on a finite-element-method (FEM) 3-D simulation analysis, various coil structures have been comparatively evaluated to find the most appropriate core structure. Furthermore, to obtain the highest coil efficiency at nominal operating condition, the appropriate number of turns design is established. Thus, according to the coil design guideline of the proposed inductive power transfer (IPT) system, the appropriate number of turns for transmitter (Tx) and Rx coils <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N_{\mathrm {1,op}}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N_{\mathrm {2,op}}$ </tex-math></inline-formula> can be appropriately selected for the high efficient operation of the IPT coils. The 2.5-kW prototypes of the IPT systems for wireless charging of AGV were fabricated and verified by simulations and experiments. The results showed that the total thickness of the coil sets including all the components is 32.0 mm for the Rx coil. The measured maximum coil efficiency for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{L} =2.5$ </tex-math></inline-formula> kW at 40-mm coil distance was 98.9% by the proposed IPT coil design procedure. The measured temperatures at the ferrite core and coil for the Rx coil were managed below 53.3 °C and 59.3 °C during 2.5-kW wireless charging, respectively, under a 10-min charging and 20-min AGV operation cycle, which provides the thermal-stable operation of the proposed IPT systems.