written 8.3 years ago by | modified 2.8 years ago by |
For a transformer, what kind of material will you choose- the one with small hysteresis area or the one with the big one?
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written 8.3 years ago by | modified 2.8 years ago by |
For a transformer, what kind of material will you choose- the one with small hysteresis area or the one with the big one?
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written 8.3 years ago by |
Hysteresis: -
Hysteresis is the dependence of the output of a system not only on its current input, but also on its history of past inputs.
The dependence arises because the history affects the value of an internal state
To predict its future outputs, either its internal state or its history must be known.
Hysteresis Loop: -
The above figure shows the behavior of a ferromagnetic core subjected to cyclically varying magnetic field.
Initially, the core is demagnetized and the strength of magnetic field “H” is set to zero. Thus point “O” marks the starting point of the curve.
On increasing magnetic strength the magnetic induction (B) increases non-linearly, as shown, up to point P, after which it remains constant.
Thus, point P is known as the saturation point.
On reducing “H” to zero, the core still remains magnetized. The residual value of “B” at point Q is called remnant induction.
On further reduction of “H” (i.e. increasing “H” in reverse direction), at point R, the core gets completely demagnetized.
The value of magnetic strength at that point is called coercive field.
As the magnetic field increases in the negative direction, again the magnetic induction appears to remain constant after a certain point S.
This is the saturation point in the negative direction.
Similarly, points T and U corresponds to points Q and R respectively as the value of “H” is increased reaching point P again.
The full cycle of magnetization and demagnetization of core is termed as Hysteresis loop.
(Note: If the time is less and the weightage for the question is not much, just mention the points and write their significance. No need to explain the process)
The area enclosed by the Hysteresis loop represents the energy loss per unit volume of the material per unit cycle.
For transformer cores, soft magnetic materials are used which has a smaller Hysteresis area.