Power Magnetics for wireless car charging: Page 2 of 3

June 30, 2016 // By Mauricio Esguerra, Magment UG
Magment is a new material, ideal to build large inductors. In contrast to metallic materials it is not manufactured with layered sheets; instead it is poured like concrete. This enables cost-efficient production, in particular in projects like charging during driving where the inductors are integrated into the road with charging power levels up to 100 kW. The efficiency depends widely on the size of the air gap, but in general it is better than with conventional materials.

shape (green)

Fig. 3 shows an example for a MAGMENT inductor and Fig. 4 a comparison with a conventional inductor. The automated design process starts with the calculation of the MAGMENT inductor design parameters for given target parameters (inductance L, rated current I and DC resistance R DC). The design algorithm looks for the dimensions giving the lowest material cost and hence the most compact design. In case outer dimensions would be constrained by device space requirements, the algorithm would take this into consideration. Based on the output design parameters a suitable coil former is chosen and the winding laid out. The housing containing the inductor is then designed according to the outer dimension of the MAGMENT material block.

Fig. 4: Comparison MAGMENT vs. conventional inductors: (a)design steps, (b) properties

 

Fig. 5: Inductor parameters relative comparison MAGMENT vs. conventional for an inductor with the same inductance value and one effective parameter:

 a) magnetic path l e   b) cross section A e   c) volume V e

 

The resulting magnetic effective parameters (Fig. 5) show the clear advantage over conventional inductors. As a general rule and due to the complete magnetic filling of the available space the ratio A e/le is much larger for MAGMENT inductors. In a relative comparison of inductors with the same inductance and either the same (a) magnetic path, (b) cross section or (c) volume the MAGMENT inductors show always a superior performance (inductance, core and winding losses) as well as cost. Fig. 6 shows a comparison corresponding to case (c) for an inductor with L=55 µH and I=60A. Notice that both the inductance is higher both for low as well as for very large currents, showing a much higher energy storage capacity.

 

 

Fig. 6: L=55 µH, I=60A inductor corresponding to design case (c), same effective volume for a MAGMENT MC40 and a FeSi (µ=60) toroid.

Beyond the technical

Design category: