Comparison of spiral and helix coils in magnetic resonant coupling wireless power transfer

The coils of magnetic resonant coupling wireless power transfer system can be classified as spiral and helix based on winding type. For the convenience of choosing them for different applications, this paper compares the effects of these two winding types on the power transfer efficiency. The efficiency and the mutual inductances of spiral and helix coils are derived through theoretical analysis. The magnetic fields of the coupling spiral/helix coils are studied through finite-element analysis, which shows that the coupling of helix coils is stronger than that of spiral coils. Besides, the experimental results also show that the efficiency of system using helix coils is a little higher than using spiral coils at the same distances.