*4.4. Insulation Technologies*

After the connection, the pad must become robust, electrically insulated and protected from external influences (water, dust, salt, etc.).

The insulating matrix around the high-frequency litz wire coil is a combination of the primary and secondary insulation. While the term secondary insulation clearly refers to resin encapsulation, the primary insulation can be divided into the litz wire enamel (standardized according to IEC 60317, IEC 60851) and the wrapping made of natural or synthetic materials.

In the context of this study, the primary and secondary insulation differ significantly in terms of production and function. For the primary insulation, the individual wires are covered with a thin, electrically insulating enamel. The additional wrapping of the high frequency litz wires is done by banding, extrusion or spinning with natural silk, nylon, polyamide, polyester, polyethylene or polyimide. Despite the large number of individual conductors, this leads to a high degree of cohesion of the strand and to a high mechanical stability during the laying of the coil. The secondary insulation ensures the protection of the electrical components against mechanical and chemical environmental impact and the dissipation of generated heat. A dielectric potting material should be selected to keep eddy current losses low and to prevent electrical breakdown [24–26].
