Construction of a radiofrequency wireless system for electric energy transmission

Abstract

ТНE PURPOSE. The objective of this study is to investigate the possibilities of longer distance resonant energy transmission applying Wireless Power Transfer (WPT) in the MHz frequency range. The planned final purpose is the energy to be transferred to all types (aerial and terrestrial) of electric vehicles (EV), mainly for the battery charging at a larger distance, compared to the normal dis-tances of WPT in use at this moment. The key to this type of High Frequency (HF) WPT system is the strong resonant inductive coupling. METHODS. This project is based on the HF power oscillations generating equipment, which original function is to generate several kW of power at MHz frequency for welding of acrylic or other plastic details. RESULTS. As a first step, the equipment was modified to supply HF power for the WPT transmitter coil, instead of supplying power to the soldering plates. The operation frequency is defined by the factory, and it is made now regulable between 8 and 14 MHz by introducing a vacuum variable capacitor. The internal powerful oscillator is based on the electronic vacuum tube ITL 5-1, a military type, capable to deliver up to 3.5 kW active power at the output. The original output had a coaxial form for supplying finally the capacitive load of the dielectric welder. This had to be reworked and a resonant loop, i.e., a capacitively compensated transmitting coil, is now connected. The intended application of this HF system is to charge the batteries of a public transport EV, possibly during its periodic stops, while the passengers will enter and leave. CONCLUSION. The applied frequency is relatively high and the distances are larger, this system still uses the magnetic field as the energy transporter, i.e., it is a near field transmission, a non-radiating system, and is expected not to produce adverse effects on the human being’s health, or to achieve a safe protection from the field.