The commonly used motor core is made of silicon steel sheet. Silicon steel is a silicon containing steel with silicon content ranging from 0.8 to 4.8%. The iron core is composed of silicon steel transformers, because silicon itself is a magnetic material magnetic ability is very strong, in the coil, it can produce large magnetic strength, which can reduce the volume of the transformer. As we know, the actual transformer always works in AC state, the power loss is not only on the resistance of the coil, but also in the iron core under the magnetization of alternating current. Usually the power loss in the core is called "iron loss", the iron loss is caused by two reasons, one is "hysteresis loss", and the other is "eddy current loss"". Hysteresis loss is the iron loss caused by hysteresis in the process of magnetization, which is proportional to the area of the hysteresis loop of the material. The hysteresis loop of silicon steel is narrow, and the hysteresis loss of the iron core of the transformer is smaller, which can greatly reduce the heating degree of the steel.