Power loss is unavoidable for transformers due to the characteristics of the lossy electrical components and magnetic materials used for manufacturing them. Transformer loss can be roughly categorized into load loss and no-load loss. Fig. 1 illustrates the circuit model of the non-ideal transformer and the losses [1]. It is estimated that there are more than 1.7 million power transformers in China, and the energy loss of these transformers is approximately 250 TWh per year. Such energy loss not only raises the total cost of the utilities but also causes considerable impact to the environment.