In the current market, the chargers are only 40-50% efficient.
- How much is the conversion and flux losses during transmission?
- Is there any way to improve the overall efficiency?
- Can a ferrite core help to reduce the losses?
Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It only takes a minute to sign up.Sign up to join this community
Because it's a transformer with poor coupling between the primary and secondary, because it's an air core so it permeability is not good (I.e how well magnetic field can pass through) and the turns on the secondary are few. So if you have poor coupling and low secondary inductance, how do you get a few watts in the secondary? Pump lots of power in the primary of which alot does not pass across. This energy is therefore wasted thus lower efficiency. Fast chargers scale this so often wireless fast chargers have fans or large heatsink because the primary energy is much higher.
A 3kW EV charging system has an efficiency of 93-95%, so not all wireless chargers are inefficient. But I assume you're talking about a wireless phone charger. The coils used to generate a magnetic field usually cheap and have a lot of leakage flux. This is due to the way a magnetic field is induced in a wire. If you think about the fields generated by the coil, the phone's internal receiver for this energy cannot cut through all of the flux.
In addition to the flux, poor air coupling, the skin effect and also uncertainty in the value of inductance also cause a lower efficiency, as in this case the circuit may not be exactly in resonance.
As you said, a ferrite core can be used to increase the magnetic flux, which also adds to efficiency.