There are two types of
Losses in an Electrical Machine. They are

- Core Loss or Iron Loss

- Ohmic Loss or Copper Loss

In this post we will discuss
about Core Loss. Core Loss is again classified into two types:

- Hysteresis Loss

- Eddy Current Loss

First we will have a look at
how the core of a Transformer looks like. But the Core Loss take place in any electrical
machine which face changing magnetic flux.

**Hysteresis Loss:**

This loss is due to magnetic
properties of iron part or core.

When the magnetic field
strength or the current is increased the flux increase, after a point when we
further increase current the flux gets saturated. When we reduce the current
from saturation to zero side the flux density starts to decrease. But when the
current value reaches zero the flux density should also be zero but it is not
zero. For zero current there is still some flux present in the material, this
is known as

**. Hence the amount of power is never recovered back. The power which gets trapped in the core of the material is lost in the form of heat.***Residual Magnetic Flux or Remnant Magnetic Flux*
Now we will consider the
mathematical part of Hysteresis Loss. The Hysteris Loss in core is given as

**P**

_{h}= K_{h}fB_{m}^{x}

^{}
Where Kh = Constant which
depends on the volume and quality of core material.

B

_{m}= Maximum flux density in the core
f = Frequency of Supply

x = Steinmetz’s constant
whose value varies from 1.5 to 2.5.

**Thus we see that Core Loss depend on Voltage as well as Frequency of Supply.**

**Eddy Current Loss**:

Eddy Current Loss takes
place when a coil is wrapped around a core and alternating ac supply is applied
to it. As the supply to the coil is alternating, the flux produced in the coil
is also alternating.

By faradays law of
electromagnetic induction, the change in flux through the core causes emf
induction inside the core. Due to induction of emf eddy current starts to flow
in the core. Due to this eddy current there will be an associated Ohmic loss
which is called Eddy Current Loss.

Eddy current losses can be
reduced by lamination in the core. Thin sheet steels must be used which are
insulated from each other. Due to insulated sheets the amount of current which
flows get reduced and hence the eddy current losses also reduces.

Now we will take a look at
the mathematical part of Eddy Current Loss. Eddy Current Loss is given as

**P**

_{e}= K_{e}f^{2}B_{m}^{2}

^{}
Where
Ke = constant whose value depends on the volume and resistivity of the core material.

Bm = Maximum flux density in
the core

f = Frequency of Supply

It shall be noted that, from
the equation of Eddy Current Loss it seems that Eddy Current Loss depends on
the frequency of supply but it is not so rather it only depends on the Supply
Voltage.

**How?**
As P

_{e}= K_{e}f^{2}B_{m}^{2}^{}

But we know that

So,

**B**where K is constant

_{m}^{2}f^{2}= KE^{2}
Thus Eddy Current Loss

**Pe = KV**^{2}

^{}

*Therefore, Eddy Current Loss only depends on the applied Voltage.***Thank you!**

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