The conversion process in power electronics requires the use of transformer components that are frequently the heaviest and bulkiest item in the conversion circuit. They also have a significant effect upon the overall performance and efficiency of the system. The designer is faced with a set of constraints that must be observed in the design on any transformer. The designer should be aware of the cost difference between silicon-iron, nickel-iron, amorphous and ferrite materials. The engineer will raise the operating frequency in order to reduce the size and weight. The magnetic materials will be reviewed for performance at the operating frequency, and at the minimum and maximum temperatures. One of the basic steps in transformer design is the selection of proper a core material. Magnetic materials used to design low and high frequency transformers. Parameters affecting others may then be traded-off, as necessary, to achieve the most desirable design.