The core sets of the ETD (Economic Transformer Design) series were developed for transformers in the range up to 1000 W and frequencies up to 500 kHz. The coilformers made of plastics in compliance with UL94 VO offer a large winding section as well as the possibility of simple extraction of thick winding wires and wire ducts for machine-suited winding. Retaining clamps can be supplied for fastening core/coilformer.