What is Hysteresis Loss : Factors & Its Applications

The term Hysteresis is an ancient Greek word and the meaning of this word is lagging behind or deficiency. It was invented by “Sir James Alfred Ewing” approximately in the year 1890 for describing the behavior of the magnetic material. We know that the rotational losses mainly occurred in all the electric motors while changing the power from electrical to mechanical. Generally, these losses are classified into different losses like magnetic, mechanical, copper, brush otherwise stray losses based on the fundamental cause as well as mechanism. So magnetic losses are two types namely hysteresis & eddy current. This article discusses an overview of hysteresis loss and its affecting factors.

What is Hysteresis Loss?

Definition: Hysteresis loss can be caused through the magnetization & demagnetization of the core when current supplies within the directions of forward & reverse. When the magnetization force is applied within the magnetic material, then the molecules of the magnetic material are aligned in one particular direction. This force can be upturned in the reverse direction; the molecular magnets internal reflection resists the reverse of magnetism which results in Magnetic Hysteresis. The internal reflection can be overcome by using the part of the magnetizing force.


Hysterisis Loss
Hysteresis Loss

Hysteresis Loss Formula

The main relationship among the ‘H’ (magnetizing force), ‘B’ (the flux density) is illustrated in the following hysteresis curve. The hysteresis loop area shows the required energy to complete a complete cycle of magnetizing as well as de-magnetizing. The loop area mainly represents the lost energy throughout this process.

The equation for hysteresis loss can be represented with the following equation

Pb = η*Bmaxn*f *V

From the above equation,

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‘Pb’ is the hysteresis loss

‘η’ is the Steinmetz hysteresis coefficient which depends on the material

‘Bmax’ is the density of highest flux

‘n’ is the Steinmetz exponent, based on the material it ranges from 1.5- 2.5

‘f’ is the frequency of the magnetic reversal for each second.

‘V’ is the magnetic material volume (m3).

The main benefit of the hysteresis loop mainly includes; the area of the hysteresis loop represents low hysteresis loss. This loop gives the retentivity & coercivity value of a material. Therefore the way to select ideal material to build a permanent magnet, then the core of the machine will become easier. From the above B-H graph, the remaining magnetism is determined & therefore selecting a material is easy for electromagnets.

The Magnitude of Hysteresis Loss

The following strip figure shows one cycle of magnetization of the magnetic material. A small strip with dB thickness over the hysteresis loop is illustrated below.

Magnitude of Hysteresis Loss
Magnitude of Hysteresis Loss

For any current (I) value, the equivalent flux value is,

Φ = B x A weber

For the minute charge ‘dϕ’ is dB x A then the work done can be given as

dW = ampere turn x change of flux

dW = NI x (dB x A) Joules

dW = N (Hl/n) (dB x A) Joules

Where H = NI/l

dW = H (Al) dB Joules

The complete work done throughout a total cycle of magnetization can be attained through integrating the above equation on both sides

dW = H (Al) dB Joules

W = ∫H (Al) dB

W = Al ∫H dB Joules

From the above equation, the loop area is ‘ʃ HdB’

So, W=Al x the hysteresis loop area otherwise work done per unit volume is W/m3 is equal to the hysteresis loop area in Joules.

If the no. of cycles of magnetization which can be made per every second then the Hysteresis loss/m3 = One hysteresis loop area x f joules per second otherwise Watts

Hysteresis Loss within the magnetic material for each unit volume can be expressed like the following.
Ph/m3 = Ƞ Bmax1.6 fV Watts

From the above equation,

‘Ph’ is the hysteresis loss within watts

‘Ƞ’ is the hysteresis constant within J/m3. This value mainly depends on the magnetic material nature.

‘Bmax’ is the highest value of the density of the flux within the magnetic material is in wb/m2

‘f’ is the no. of cycles of magnetization which is made for each second

‘V’ is the magnetic material volume in m3

Factors Affecting Hysteresis Loss

There are different kinds of factors that affect the hysteresis loss like the following.

  • The loop of the hysteresis is narrow; the material will be magnetized very easily.
  • Similarly, if the material doesn’t get magnetized simply, then the hysteresis loop will be large.
  • At different values of ‘B’, different materials can saturate, so the loop height will be affected.
  • This loop mainly depends on the material nature.
  • The loop size, as well as shape, mainly depends on the first position of the specimen.

How do we Reduce Hysteresis Losses?

Hysteresis losses can be reduced by using material that has less area of the hysteresis loop. Hence, high grade or silica steel can be used for designing the core within a transformer because it has extremely less area of the hysteresis loop.

To reduce this loss, the special core material can be used which reaches zero/non-zero flux density once the flow of current is removed.

These losses can be decreased by increasing the no. of laminations which are supplied through fewer gaps among plates. Hysteresis loss can be decreased by choosing a softcore that has less hysteresis. The best example of this is silicon steel etc. These losses mainly depend on the density of flux, the laminated core, and frequency.

Applications

The applications of hysteresis loss include the following.

The hysteresis loop provides the data of coercivity, retentivity, susceptibility, permeability & loss of energy throughout a single cycle of magnetization for every ferromagnetic material. So, this loop will assist us in choosing the correct & appropriate material for a specified purpose. Some of the examples of hysteresis loss include permanent magnets, electromagnets, and the core of the transformer.

  • These are used in ferromagnets.
  • Hysteresis loops are significant in the designing of numerous electrical devices

Thus, this is all about an overview of hysteresis loss which includes formula, factors, and applications. The main properties of these losses mainly include Retentivity, Residual Flux, Residual Magnetism, Coercive Force, Permeability, and Reluctance. Here is a question for you, what is the unit of hysteresis loss?

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