Design issues of a core-less transformer for a contact-less application

A set of rules for designing coreless transformers for contactless applications is presented in this paper. In contactless transference of energy, there is a relative big separation distance between the coils, so coupling is low. Several simulations have been performed with an FEA tool studying different technologies and winding strategies in order to quantify the improvements in coupling and resistance for different gaps. The analysis has been done for the transcutaneous transformer of a human-body implant, but the conclusions can be extended to any kind of coreless transformer for a contact-less application. The results are consistent with the measurements