Core loss is referred to as "iron loss", also known as "core loss" and "excitation loss".

It refers to the power loss caused by alternating or pulsating magnetic field in magnetic materials, which is expressed in the form of heat.

It is divided into hysteresis loss and eddy current loss.

Hysteresis loss is the energy consumed by ferromagnets due to hysteresis in the process of repeated magnetization. The main reason is domain rotation friction. Hysteresis means that when the magnetic state of ferromagnetic materials changes, the magnetization lags behind the magnetic field strength, and there is a hysteresis loop relationship between its magnetic flux density B and magnetic field strength H. After one cycle, the hysteresis loss per unit volume of iron core is proportional to the area of hysteresis loop. This part of energy is converted into heat energy to heat up the equipment and reduce the efficiency. It is an integral part of iron loss in electrical equipment, which is undesirable in equipment such as AC motor. The hysteresis loop of soft magnetic material is narrow, and its hysteresis loss is relatively small. Therefore, silicon steel sheet is widely used in motor, transformer, relay and other equipment.

Eddy current loss is the energy loss caused by the induced current in the conductor when the conductor moves in a non-uniform magnetic field or is in a time-varying magnetic field, which is called eddy current loss. The closed current lines formed inside the conductor are called eddy current (also known as Foucault current)

Motor core loss can be reduced by the following measures:

1. Reduce the magnetic density and increase the length of the iron core to reduce the magnetic flux density, but the iron consumption of the motor increases accordingly;

2. Reduce the thickness of iron chips to reduce the loss of induced current. For example, using cold-rolled silicon steel sheets instead of hot-rolled silicon steel sheets can reduce the thickness of silicon steel sheets, but thin iron chips will increase the number of iron chips and motor manufacturing cost;

3. Cold rolled silicon steel sheet with good magnetic conductivity is used to reduce hysteresis loss;

4. High performance iron chip insulation coating is adopted;

5. Heat treatment and manufacturing technology, the residual stress after iron chip processing will seriously affect the loss of motor. During silicon steel sheet processing, cutting and punching and shearing stress have a great impact on the loss of iron core. Cutting along the rolling direction of silicon steel sheet and heat treatment of silicon steel sheet can reduce the loss by 10% - 20%.