the ETD core design is a further development of E cores. They are optimized for use in SMPS transformers with switching frequencies between 50 and 200 kHz. The designation ETD (Economic Transformer Design) implies that this design achieves maximum throughput power related to volume and weight of the total transformer. Shielding is somewhat improved compared with E cores. The matching coil formers are suitable for many winding types and can be handled on automatic equipment.