Structural Design of Litz Wires for Reducing AC Transport Current Loss Using an Equivalent Circuit Model Considering the Path of All Strands

Litz wires are generally fabricated based on the proprietary know-how of wire manufacturers. Therefore, the design guidelines for the conductor structure of low-loss Litz wires have not been clearly established. In this study, we investigated the effect of differences in the conductor structure on the AC resistance using the equivalent circuit model considering the path of all strands. Moreover, we proposed design guidelines for the conductor structure of Litz wires to reduce AC resistance originating from strand paths. Furthermore, we prototyped Litz wires according to the proposed design guidelines and compared the AC resistance of the proposed Litz wires with that of commercial Litz wires. As a result, the AC resistance of the prototyped Litz wires according to the proposed design guidelines was reduced compared to that of the commercial Litz wires. Moreover, the quality factor of the spiral coil using the proposed Litz wire was higher than that using the commercial Litz wire. From the above results, we experimentally clarified that the proposed design guidelines for the conductor structure of Litz wires are effective in reducing the AC resistance originating from strand paths.