Answer / joy

Your generator will be damaged. The reason being
that the transformer impedance as well as
impedeance of the entire 11kv side will be loaded
on the generator. Besides the inrush current which
the transformer will take when you charge it. This
will lead to the dropping of pf of the generator,
leading to the heating of its windings. Also you
have to make sure there are no chances of the
"normal" 11kv source being re applied when the
generator is being used to charge the 11kv side. Or
else the generator will experience a shearing of
its rotor.

Answer / a. magesh kumar

My understanding is two 900 KVA generator, alternatively
feeds the supply to transformer (one at a time), the
transformer step down voltage 11KV/ 400V (3KVA). This 440V
feeds to connected load (seconday side of the transformer).

Ur question: In the event of Power failure 11KV side
(primary), what will be the inrush current?

whether u r asking short circuit current or else?



Inrush rush Current:



AC power may happen to be applied to the primary winding of
a power transformer at any point in the voltage cycle.
Excessive current inrush can result if the primary voltage
suddenly goes from zero to a high value rather than
increasing sinusoidally as it does during normal operation.
Excessive inrush current to a large transformer may not
only blow a fuse, trip a breaker, cause a sharp dip in
mains voltage, damage transformer windings, or damage
electrical supply circuits, it also induces a very large
voltage spike in the transformer secondary winding. Large
secondary voltage spikes can breakdown winding insulation,
damage rectifiers, and damage other power supply components
When switching power supplies are first turned on, they
present high initial currents as a result of filter
capacitor impedance. These large filter capacitors act like
a short circuit, producing an immediate inrush surge
current with a fast rise time. The peak inrush current is
several orders of magnitude greater than the circuit's
steady state current. This power surge can seriously damage
other components


Calculate the Steady State Current:
(Available data from ur mail)

Transformer power: 3 KVA

Primary Voltage : 11 KV

Secondary Voltage : 415 V

Efficiency : 85 % (assumed)

Impedance : 4 % (assumed)



Steady State Current: (KVA of transformer) / (efficiency
of transformer) X (Minimum Input voltage)

: 3 KVA / (0.70) X (415)

: 10.32 Amps.

Short Circuit Calculation: 3 KVA / 415
: 7.2 A
: 7.2 * 25 (impedance)

: 180.7 A (0.18 KA)



Short circuit current is 187.5 Amps.

Answer / harsh

first answer is correct.
the generator will never damage while giving reverse
feedback.
its only to chack whether is there any fault in our cables
or any other machinery or furnaces.

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