A Multi-MHz IPT-link Developed for Load Characterisation at Highly Variable Coupling Factor

Abstract

This paper presents the development and characterisation of an inductive link to assess and compare inductive power transfer (IPT) systems that operate at 6.78 or 13.56 MHz. First, the properties of two equal air-core coils were obtained from simulations and corroborated experimentally. Then, the coupling factor between the coils was calculated in function of separation and misalignment. A receiving-end circuit, comprised of a capacitance and a resistive load, was also characterised in order to reflect different loads to the transmitter at different tunings and couplings, and therefore represent the effects produced by changes in coupling and variations in the rectifier's input impedance. The link was tested, firstly using a Class E inverter and then a load-independent Class EF inverter, both at power levels lower than 200 W. The reflected load was changed by altering coupling, and the tuning capacitance. A comparison between these inverter topologies handling highly reactive loads is shown here for the first time.

A Multi-MHz Wireless Power Transfer System With Mains Power Factor Correction Circuitry on the Receiver

“…The IPT load used in the first two experiments is an RLC circuit developed in [12] which reflects a resistive load on the transmit coil. The reflected load (R eq ) was calculated at 1.55 Ω when the IPT load is positioned at 18 cm from the transmit coil, and at 3.55 Ω when positioned at 15 cm.…”

“…The two 20 cm air-core pcb coils (IPT link in Fig. 1) used in the case study were characterised in [12] using electromagnetic simulation software and a Keysight E4990A impedance analyser. Coupling was also characterised in relation to distance and misalignment of the coils in [12], which allows calculating the induced emf on the receive coil as a function of i p and…”

Dynamic Capabilities of Multi-MHz Inductive Power Transfer Systems Demonstrated With Batteryless Drones

“…The transmitting-coil consists of a two turn circular printed circuit board coil with an external diameter of 20 cm and no magnetically permeable materials. The shape of this coil, previously characterised in [24], can be seen in Fig. 5.…”

“…where X res is residual reactance: This set of equations is a practical solution to achieve load independent operation whilst operating at a lower input voltage than in our first prototype [19] or the solutions presented in previous works using this tuning methodology for Class EF inverters [24], [34], [35], [36]. For this design, it is convenient to operate at a lower input voltage since the implemented dc power source is most likely to be of low voltage.…”

A 13.56 MHz Inductive Power Transfer System Operating with Corroded Coils

“…Since air-core PCB coils allow achieving high Q-factors (>500) when operating at the two first ISM bands (6.78 MHz and 13.56 MHz) [13], two of the two-turn circular PCB coils with an external diameter of 20 cm and no magnetically permeable materials utilised in [13] were selected to conduct the experiments.…”