Answer / thwosif_emrson

How to find out Iron & Copper lossed in transformer:-

1>Iron Losses:-
Iron losses are due to hysteresis and eddy-current loss
produced by the alternating magnetic flux in the iron core.
The iron losses are almost independent of the load and thus
are considered to be constant at all loads.

In order to determine the iron loss, one winding of the
transformer (whichever is the most convenient) is open
circuited. A voltage is applied to the other winding and
the power (watts) in this circuit is measured. This power
represents the iron losses. Copper losses under these
circumstances are negligible.


2>Copper Losses:-

Copper losses are the heat losses in the windings due to
the electrical resistance of the windings. The copper
losses are proportional to the square of the current and
therefore to the kVA output. These losses can be calculated
from the design data but can also be measured by a test.
This test is known as the short circuit test for copper
losses.

The short circuit test is carried out by short circuiting
one winding, thus causing the transformer to behave like a
coil having a leakage impedance equal to that of both
windings. A low voltage is applied to the open winding
sufficient to circulate full load current through the open
winding due to transformer action in the short-circuited
winding. Under these conditions, the flux set up in the
core is so small that iron losses can usually be neglected
and the wattmeter would give the total copper loss.

Answer / arun

In transformer 2 types of losses
1.constant losses(core losses and eddy current losses)
this loses estimated by conducting open circuit test
in oc test we apply rated voltage .so we obtain total constant loses
2. variable losses (cu loses)
this loses estimated by conducting short circuit test.
in sc test we pass rated current through windings of transformer .so we get the rated copper losses.
cu losses vary with load but by conducting sc test we obtain max cu loss

Answer / gabriel pop

I think v is volume of the core not voltage.

Anyway, if someone know an accurate method to calculate
power losses in power transformer please tell me.

Answer / maharajan

hysteresis loss =Bmaxpower 1.6 fv
eddy current loss= Bmaxsqrfsqrtsqrv
B-flux density
f-frequency
t-thickness of the core
v-voltage
in this loss all are constant so core loss is almost const
for all load
load loss=Isqrr
so it is depending upon the load and the internal resistance
for high efficiency core loss=copper loss

why earth fault current is always less than the o/c

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