I was involved with high-voltage power supplies in which transformers were wound using 3019-sized ferrite cores. Transformer structures were essentially the following: Figure 1 Pot core based ...

TDK has introduced ferrite ‘E’ cores up to 40 x 80 x 160mm for industrial applications such as motor drives. The largest one is made from N87 ferrite, while most of the rest also come in N88 or N97.

Soft magnetic materials (materials that can easily be magnetized) come in many forms. For switchmode power supply flyback transformers and chokes, we would consider gapped ferrites, Iron powder, ...