Losses in Transformers


Types of losses in the transformers

There are two types of losses in transformers. Iron loss and copper loss.
Iron loss also called as a constant loss, while copper loss is also called as a variable loss these are depends upon load current.

A. Copper loss

 Copper losses. Copper losses (I2R) are the resistive heating losses in the primary and secondary windings of the transformer. They are proportional to the square of the current in the windings.

B. Iron loss
These are also in two types 

1. Eddy current losses. Eddy current losses are resistive heating losses in the core of the transformer. They are also called swirling losses. They are proportional to the square of the voltage applied to the transformer.

Pe= Kef2 (Bmax)2t2\ρ                  
Where;
Ke = proportionality constant
f    =  frequency
Bmax = maximum flux density
t = thickness
Ρ = resistivity

Now we have to keep ratio of voltage to frequency constant for linearity of core and to avoid over fluxing problem.
Now we will take the effect of E\f ratio in above for eq.

When e\f is constant, Pe  ∝ f2
Otherwise Pe  ∝ V2

2. Hysteresis losses. Hysteresis loss is due to reversal of core due to alternating flux. These are associated with the rearrangement of the magnetic domains in the core during each half-cycle. They are a complex, nonlinear function of the voltage applied to the transformer.

Ph= Khf (Bmax)xV 
Where;
Kh = proportionality constant
f    = frequency
Bmax = maximum flux density
V = volume

Now we have to keep ratio of voltage to frequency constant for linearity of core and to avoid over fluxing problem.
Now we will take the effect of E\f ratio in above for eq.

When e\f is constant, Ph  ∝ f
Otherwise Ph  ∝ f1.6-1  ∝  f-1
                         
 Leakage flux The fluxes Φ1L and Φ2L. which escape the core and pass through only one of the transformer windings are leakage fluxes. These escaped fluxes produce a self-inductance in the primary and secondary coils.

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