what is inrush current in transformer?

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what is inrush current in transformer?..

Answer / vidhya

Inrush current or input surge current refers to the
maximum, instantaneous input current drawn by an electrical
device when first turned on.Alternating current electric
motors and transformers may draw several times their normal
full-load current when first energized, for a few cycles of
the input waveform. .
When a transformer is first energized a transient current
much larger than the rated transformer current can flow for
several cycles. This is caused because the transformer will
always have some residual flux density and when the
transformer is reenergized the incoming flux will add to
the already existing flux which will cause the transformer
to move into saturation.this transient current is called as
inrush current.

Is This Answer Correct ?    56 Yes 5 No

what is inrush current in transformer?..

Answer / aryan

when we give supply to transformer transformer charge and
flux is produced and when the supply is cutoff some flux is
been remained which is known as residual flux.

when we again charge the transformer the flux produce is
combination of flux and residual flux and the current
produced due to it is known as inrush current

Is This Answer Correct ?    77 Yes 29 No

what is inrush current in transformer?..

Answer / sudhir

inrush current is refers to maximum, instantaneous input
current drawn by electrical device when first turned on.
when a T/F is first energized a transient current much
larger than the rated T/F current can flow for several
cycles.this ts caused because the T/F will always have some
residual flux and when T/F is energized the incoming flux
will add to the already existing flux which will cause the
T/F to move in to saturation.
due to this the starting current is double the rated
value. this us not a fault, our protecting system is
designed such a way that it can with stand with this inrush
current without any tripping.

Is This Answer Correct ?    32 Yes 4 No

what is inrush current in transformer?..

Answer / amit mewada

Inrush Current will be generate only during switching on
the transformer.
When we switching on the transformer, its flux is also
start increases with increases in voltage. Normally flux
will be 90 degree lags behind voltage but during starting
condition like first half cycle (this will also continue
for other few cycles) flux peak will increases approx two
times than its normal value. Similarly current is also
increases approx two times from its normal peak value. This
will be more dangerous when any residual flux is available
in transformer.
Inrush current has normally two parts. First is DC
component & other is 2nd Harmonics.

Is This Answer Correct ?    24 Yes 7 No

what is inrush current in transformer?..

Answer / malkit

When a transformer is first energized a transient current
up to 10 to 50 times larger than the rated transformer
current can flow for several cycles. This happens when the
primary winding is connected around the zero-crossing of
the primary voltage. For large transformers, inrush current
can last for several seconds. Toroid transformers can have
up to 80 times larger inrush, because the remanent
magnetism is nearly as high as the saturation magnetism at
the "knee" of the hysteresis loop. This is caused because
the transformer will always have some residual flux density
and when the transformer is reenergized the incoming flux
will add to the already existing flux which will cause the
transformer to move into saturation. Then only the
resistance of the primary side windings and the power line
are limiting the current.

Is This Answer Correct ?    16 Yes 2 No

what is inrush current in transformer?..

Answer / s das

When a transformer first energised, the transient input
current can be 10-50 times larger than the normal operating
current for first several cycles. This is called inrush
current. If the trans. is energised at voltage zero
crossing the maximum flux is requirred to support the
voltage is double the normal flux. This is because the rate
of change of the flux(decides the voltage drop against the
inductance) should be same as steady state condition to
support same input voltage, but the flux is started from
zero in case of transient and started from negative maximum
value of flux in case of steady state for zero crossing
voltage of positive cycle. Tran. normally operats at the
knee point of hysteresis loop, the tran. will enter into
saturation zone and a huge current will be requirred to
generate double flux. In saturation zone, the inductance of
the core will be decreased and a considerable amount of
voltage(compared to drop against the coil) will be dropped
against the coil resistance9due to high current). The
voltage drop against the inductance of the coil is less
compare to normal condition and flux is not requirred to be
double. This could be severe if there is positive residual
flux at the time of energise at zero crossing of voltage's
positive half cycle. So the inrush current depends on the
time of energise, resistance of the coil and the residual
flux.

Is This Answer Correct ?    2 Yes 0 No

what is inrush current in transformer?..

Answer / burka

inrush current;jechuun current yeroo tranformariin dalagu
filux waliin tranformarii keessatti hafuudha.

Is This Answer Correct ?    1 Yes 0 No

what is inrush current in transformer?..

Answer / anish pathak,kptcl(mysore)

When a transformer is first energized a transient current up to 10 to 50 times larger than the rated transformer current can flow for several cycles. This happens when the primary winding is connected around the zero-crossing of the primary voltage. For large transformers, inrush current can last for several seconds.

Is This Answer Correct ?    1 Yes 0 No

what is inrush current in transformer?..

Answer / amit dubey

When we charge the Trafo, flux will get generated there,
but when we make get it isolated some flux will remain
there.Again while we charge the trafo,remaining flux will
oppose the present flux hence high current will get
generated, which is very dangerous for trafo. The current
produced as n above condition is called Inrush Current,
which is flowing for very minor time ()

Is This Answer Correct ?    8 Yes 8 No

what is inrush current in transformer?..

Answer / manish shastri, elect guru

To understand this phenomena, we need to recall one
fundamental that "any situation that calls for
instantaneous change in flux linkage results in large
magnetising inrush current".

When a transformer is connected to a power system with its
secondary ckt open/ no load, assymetrical flux is in
quadrature with voltage (it actually lags the voltage by 90
Degree). The amount of flux produced depends on when
circuit breaker or switch is closed. Also, the assymetry of
flux will correspond to assemtry of voltage wave.

If breaker is closed at point when voltage wave is passing
thro it's ZERO, the assymetrical flux can attain the value
of 2 PHI MAX. If the value of residual flux at this time is
PHI (res), than total flux will be 2 PHI MAX + PHI (res).

If breaker is closed at point when voltage wave is passing
thro it's maximum, flux produced will be PHI MAX.

The linking of flux with the transformer winding will be
limited by core saturation and winding inductance. For flux
of level (2PHI MAX or PHI MAX), core will go into
saturation, meaning flux linking will be thorugh winding.
As flux in winding can not change instantaneously, it will
be linked thro air core inductance.

As air core inductance value is very small, to produce
required amount of flux in winding, the current required is
of very large value.

This can be easily understood by formula I=N*PHI/L. As L is
very less, magnetising inrush is very high.

The magnitude of the inrush current is limited by the air
core inductance of the windings under extreme saturation
conditions. A transformer with concentric windings will
draw a higher magnetising current when energised from the
LV side, since this winding is usually on the inside and
has a lower air core inductance.

Hope this explains the phenomena of magentising inrush
which many times lasts few seconds and goes as high as 6-10
times and consists mainly DC, 2nd Harmonics and 3rd
Harmonics.

Is This Answer Correct ?    0 Yes 0 No

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