What is hysteresis loss?

Hysteresis loss is a type of energy loss that occurs in magnetic materials when they are subjected to changing magnetic fields. This happens due to the lagging of the magnetic field inside the material behind the changes in the magnetic field applied to it.

Here are the steps to understand it:

1. Magnetic materials have tiny magnetic domains, each of which acts like a tiny magnet. In an unmagnetized material, these domains are randomly oriented, so their magnetic effects cancel each other out.

2. When a magnetic field is applied to the material, these domains start to align with the field. This alignment process takes some time, so the magnetic field inside the material lags behind the applied field. This is the phenomenon of hysteresis.

3. When the applied magnetic field is removed, the domains do not immediately return to their random orientations. Instead, they remain partially aligned, causing the material to retain some magnetism. This is known as magnetic remanence or residual magnetism.

4. If the magnetic field is then reversed, the domains have to realign in the opposite direction. This realignment process again takes time, causing further hysteresis lag.

5. The energy required to change the alignment of the domains is lost as heat. This is the hysteresis loss. It is proportional to the area of the hysteresis loop, which is a graph of the magnetic field strength in the material versus the magnetization of the material.

6. Hysteresis loss is a major factor in the efficiency of transformers and other AC-operated devices. It can be reduced by using magnetic materials with narrow hysteresis loops, such as soft iron.