I am currently designing inductive power transfer system. I used H-bridge to invert the dc to AC, I used series capacitor bank at the transmitter and the same at the receiver. Used Extremely fast switching Schotky diodes at the receiver to reduce the losses. Till now i managed to input 140 Watts and output 70 watts so 50% efficiency. I selected the coils for high current from Wurth Electronics and matched the capacitor bank value to get a resonance frequency to correspond for the highest Q-factor from the datasheet. But when i adjust the H-bridge frequency to this value i don't get any power. i had a function generator and varied the frequency and i found that 2 frequencies give good induction, one is lower and the other is higher than the calculated resonance frequency and the lower frequency value has higher efficiency.
To get this efficiency the coils are right above each other with no spacing and i want to create at least 1cm space between them.
I also noticed that as i increase the input voltage to the H-bridge the efficiency decreases until i decrease the input frequency to the bridge.
So how can i automatically decrease the frequency with the voltage? and improve the efficiency and distance?
Thank you for the article Professor. I will check it and get back to you if i have any question, if it is ok with you.
Dear Mahmoud,
what do you built is a wireless inductive coupled power transfer system. One can consider that your wireless transfer system is composed of two resonance circuits coupled with each other with the primary coil transfers magnetically the electrical power through magnetic induction. Then at the output of the resonance circuit you have a rectifier circuit followed by an inverter circuit.
So, the overall efficeincy of the system is the resultant efficeincy of the three subsystems, the inductive energy transfer system, the rectifier subsystem and the inverter subsystem.
An efficiency of 50 percent is too low. Theoretically you have enough head room to enhance it by decreasing the losses in every subsystem.
The primary side for sure may have its effects on the efficiency as contains a rectifier and an oscillator.
The double resonance is well known in the over coupled resonance circuits The double resonance is called the saddle behavior with the transmission coefficient of the lower resonance is greater than that at the higher frequency. As the coupling coefficient increases, the splitting of the two frequencies from the center frequency increases.
My advice to you is to work your system at the highest possible voltage to boost the efficiency. You may use also ferrite cores to steer the magnetic fields.
Best wishes
Thank you professor Abdelhalim for your response.
I will use your advice and work on improving the efficiency of each subsystem on its own and i will also try to increase the supply voltage.
Thank you again.
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