Study of the conducted emissions of an IPT system composed of an array of magnetically coupled resonators

In this paper the conducted emissions generated by an inductive power transfer (IPT) system composed of an array of magnetically coupled stranded-wire resonators and powered by an H-bridge inverter (operating at a resonant frequency of 147kHz) are assessed for arrays with different numbers of resonators, different termination impedances and for a constant power of 5W absorbed by the termination impedance. It was found that the peak values of the disturbance voltage obtained through measurements, in the frequency range from 150kHz to 30MHz, depend on the equivalent impedance that represents the impedance of the array after removing the resonator connected to the power source. More specifically, the highest peak values of the disturbance voltage were found at 150kHz and 294kHz (the former frequency is close to the resonant frequency and the latter is its second harmonic) for an even number of resonators and a high termination impedance or for an odd number of resonators and a low termination impedance, situations which both correspond to a low value of the equivalent impedance. Finally, when a termination impedance close to the equivalent impedance of an infinite array of resonators is used, the disturbance voltage values are approximately the same for any number of resonators.