Transformer Design

Transformers used in power electronics applications normally serve to provide isolation from the input mains and to reduce voltage stress on switching components by more closely matching the operating voltage to the switch voltage ratings. The design methodology of the transformer optimizes the energy transfer from the input winding to the output winding through electromagnetic induction in a given application, in terms of minimizing the core and winding losses. This chapter establishes the design rules to select the core and winding in a transformer. The main specifications are power rating, frequency and temperature rise. When the core and winding are selected, the overall transformer is evaluated for temperature rise and efficiency. Several examples are included to illustrate the design methodology, including a centre-tapped rectifier transformer, a forward converter and a push-pull converter. The chapter also talks about transformer insulation, including operational insulation, and double insulation or reinforced insulation. Controlled Vocabulary Terms core loss; driver circuits; energy exchange; magnetic flux; transformers