Answer / gaurang

As per Equation

P=route 3 * V *I* cos phi
I=KVA/ rout 3 * V
So for 2000 KVA Transformer and considering Volatge 415 V.
I=2000/1.732 * 0.415
I=2782 A
Considering the breaker rated capacity selection above 2782
A as per Mfg. std.
Circuit breaker capacity will be of 3200 A.

Answer / ashish patil

First find the full load current of transformer.2MVA
transformer current value comes near 2915 A. consider
overloading capacity 10%. it comes near 3100.
so u can select indor Air circit braker or 4000A
capacity.

Answer / solver

gaurang you are right
also mukund is right

Dear ashish & sareer,

always remember that the LT side breaker of transformer
is only selected based on rated capacity of LT winding.
i.e. 2782 A in this case.
& no overloading is considered beyond capacity of
transformer winding.
besides that transformer is loaded to 80% of its capacity.
This makes the load current even lesser than the rated.


Hope you are satisfied by this answer

Answer / sareer ahmad lone

Ans.First you have to find out the full load current of the
transformer that is IL=2915A then as per NEC you have to
give atleast 25% that is 2915x1.25=3643.75A.So the nearest
size of Circuit Breaker shall be 4000A.

Answer / mukund

it is necessary to know what is the voltage rating of
transformer
many of the times 2000 kva x'mer are 22/11 kv less than
that are generally 22/0.415kv or 11/0.415kv first you
clear that

Answer / foolinla

The capacity of a transformer depends on its rated voltage
and current. The load current varies depend on the voltage
of the transformer.
If this 3 phase 2000KVA has a primary voltage @ 4160V, then
the primary current is 278A (2000000/1.73/4160V)
If the secondary of this 2000KVA is 480/277 then the
secondary full load current is 2408A (2000000/1.73/480).
If the secondary of this 2000KVA is 208/120 then the
secondary full load current is 5558A (2000000/1.73/208).

Answer / arun r

depend upon fault current & fault during time

Answer / aravind

WHile selecting any Circuit breaker the transfoemer rating
and Impedance should be considered.

Answer / khadu ali murthuja

Transformer rating already given=2000KVA
Select Air circuit breaker ie secondary current multiplying with 1.6A to the rating of the transformer.
secondary current = 2000×1.6
= 3200A Air Curcuit Breaker Required.
since 1KVA =1.6A

how to find out primary current.

the relation ship between voltage and current.

V2/V1=I1/I2
415/11000=I1/3200
I1=120A...

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