but the perimeter of a normal wire with the same cross-sectional area would be 2π a . This means that the resistance of the Litz-wire would be around 2.33 times smaller, according to (94). So Litz wire seems to be the perfect candidate to increase the total efficiency of a wireless power transfer system [3]. But it is not the case. The reason lies in the nonconsidering proximity effect in the adjacent conductors of the Litz wire. The proximity effect results in current redistribution, causing it to flow only on the outward-facing surfaces of the conductors forming the litz wire. With increasing frequency, this effect will be intensified.