An experimental evaluation of losses in planar Litz structures

Planar magnetic structures are gaining popularity in power electronics, however they have drawbacks in high current and high frequency applications. The main drawback is the poor current distribution in the planar conductor, which arises from the proximity and skin effects. This leads to a high AC resistance, which increases the conduction losses. In This work the principle of the Litz wire is applied to the planar conductor. It has already been demonstrated that this technique can reduce the effective AC resistance of the planar conductor. To date however it has only been demonstrated at very low signal levels through impedance measurements. In This work the reduction in loss is demonstrated experimentally at high powers under real operational conditions. The work is carried out with various configurations of Litz interconnections, and the losses characterised by means of impedance and calorific measurements.