Reduced Ferrite Double D Pad for Roadway IPT Applications

Roadway inductive power transfer presents an opportunity to provide a robust and user friendly system for electric vehicle charging by utilizing magnetic couplers (pads) embedded in the roadway. Roadway pads are expected to have a long service life but existing pads use a large quantity of the brittle magnetic material ferrite, which may break in the harsh environment of a roadway. This article shows what happens when the volume of ferrite material is reduced from an example double D pad to minimize the quantity and size of ferrite that needs to be protected. Also presented are design insights into the placement of a reflection winding that helps shape the field in the absence of the majority of ferrite. The final selected example design reduces the leakage magnetic field where a person may be present by 43%, at the expense of an increase in primary VA of 73% from the original double D pad. The final presented pad reduces the ferrite volume by 86% compared to the original example double D pad, is only 50 mm thick, and is shown to have a measured dc-dc efficiency of 91% when delivering 4.7 kW to an available secondary.

Automated summary

This article discusses the optimization of magnetic coupler design in roadway inductive power transfer systems, aiming to increase efficiency by reducing the volume of ferrite material. Through optimized design, it is possible to reduce ferrite usage, lower leakage magnetic field, and improve charging efficiency.