Verification of the Positioning of Battery Electric Vehicles over an Inductive Charger, by Estimating the Coupling Through a Resistor

Abstract:

Battery-powered electric vehicles have arrived on the streets. Most electric vehicles have to be recharged by plugging-in a cable. A wireless charging system with induction makes the process more comfortable. The primary coil， build in the parking lot， transforms the electric energy into field energy. The secondary coil， build in the vehicle， receives the energy and transforms it into electric energy and recharges the battery. To ensure safe and efficient charging， the coil pair must be coupled sufficient. This is done by positioning the vehicle well enough over the primary coil.This paper presents a simple and cost-effective way to verify whether the coupling between the coil pair is sufficient enough for charging. A resistor， on the secondary side， simulates the load of the battery on the wireless charging system in defined operating condition. The voltage across the resistor can be used to estimate the coupling between the coils. This relates to the positioning of the vehicle. The paper explains the concept on the basis of mathematical and physical principles. The results are evaluated on a real wireless power transmission track.