Hello, I am a student doing a research at university.I am working on wireless electricity transfer.I have two coils forming transmitter and Receiver. My coils are with diameter 17 cm. I have reached 53% efficiency in 15cm.And It is not increasing anyhow whatever I do. I want to ask where other 50 % of energy go? Plus, I have reached 50% with 15V input. And I expected that increasing the voltage ,would increase the efficiency.But Increasing the input voltage , causing drop in efficiency. Why is that? I can reach 50% efficiency in 20 cm too. But ,cannot get more then 53% in 15 cm.Why?