What is hysteresis loss?

Answer 1

If the magnetic field applied to a magnetic material is increased and then decreased back to its original value, the magnetic field inside the material does not return to its original value. The internal field 'lags' behind the external field. This behaviour results in a loss of energy, called the hysteresis loss, when a sample is repeatedly magnetized and demagnetized. The materials used in transformer cores and electromagnets are chosen to have a low hysteresis loss. Similar behaviour is seen in some materials when varying electric fields are applied (electric hysteresis). Elastic hysteresis occurs when a varying force repeatedly deforms an elastic material. The deformation produced does not completely disappear when the force is removed, and this results in energy loss on repeated deformations.

Answer 2

Hysteresis is the dependence of a system not only on its current environment but also on its past environment. This dependence arises because the system can be in more than one internal state. To predict its future development, either its internal state or its history must be known.[1] If a given input alternately increases and decreases, the output tends to form a loop as in the figure. However, loops may also occur because of a dynamic lag between input and output. Often, this effect is also referred to as hysteresis, or rate-dependent hysteresis. This effect disappears as the input changes more slowly, so many experts[who?] do not regard it as true hysteresis.

Answer

Hysteresis losses occur in the magnetic circuits of Transformers and other electrical machines, and is a function of the material used in the manufacture of the magnetic circuit. It represents the energy required to magnetise and demagnetise a sample of that ferromagnetic material.

'Soft' ferromagnetic materials, such as silicon steel, are easily magnetised and demagnetised and have relatively-low hysteresis losses, whereas 'hard' ferromagnetic materials are relatively difficult to magnetise and demagnetise, and have relatively-high hysteresis losses.

Hysteresis losses are represented by the area of the hysteresis 'loop' created when a material's flux density is plotted against changes in magnetising force over one complete cycle of magnetising current; the larger the area, the greater the hysteresis loss.

Answer 3

Hysteresis is an output's dependence on both current and historical input. This is necessary because the current state is affected by historical inputs.