Answer / sameer

I think answer 5 is correct

Answer / electrical in detail

(1) Core Balance or Magnetic Balance of a transformer is well needed. This test is carried out to determine inter turn faults or magnetic imbalance in transformer.

(2) It is very well known that each turn of the winding of a transformer is isolated from other turn through appropriate insulation. A properly designed transformer of 11 KV / 415 V means applying 11 KV on one side will produce 415 V on other side and vice versa. Now if insulation between turns of a winding loses their property, then turns of the winding are short circuited and this situation is called inter-turn fault.

(3) When an inter-turn fault occurs, magnetic property of transformer is imbalanced and this imbalance is conveyed to secondary side of the transformer as the two windings are connected magnetically. It means voltage that is produced by mutual induction will also get affected. To identify this imbalance, magnetic or core balance (in fact, imbalance) test is carried out.

(4) This test is generally performed on STAR side of the transformer. Forgetting the international nomenclature, let us name three leads of STAR side as R1, Y1 and B1 while that of other winding as R2, Y2 and B2.
B1 is kept opened. A supply of say 440 V is applied between R1 and B1. Next step is to measure various voltages between different phases:

V (R1-Y1) = V (R1-B1) + V(Y1-B1)
For example,
440 V = 250 V + 190 V

(5) As both the windings are connected magnetically, applying voltage to star winding will induce voltage on other winding. Induced voltage in other winding shall be in same proportion to applied voltage at star side. But if, any inter turn shorting is there, the voltage induced on the secondary winding will not be in proportion to the applied voltage.

This is an indicative test only. Accurate results can be obtained in conjunction with other tests.

Answer / joshi nikhilesh

appliade volage IN H.V SIDE APPLIADE VOLTAGE IN L.V SIDE

RY rn

measured voltage measured voltage

RY,YB,BR rn,yn,bn rn,yn,bn

and reapit this all step appliade YB,BR yn,bn and
measured abouve step

Answer / k kiran kishore

This is kiran kishore from IEMCO MUSCAT

Can any one explain why this magnetic balance test performed
on star side only? is there alternative methods for this
test? in my knowledge 1. phase in method
2. phase out method.

give me the clear idea. can u explain if tertiary winding
also present then how this test going to be performed?

i hope you guys will give me clear explanation to all my
quires.
THANKS&REGARDS
K KIRAN KISHORE

Answer / jac

Additional Question Regarding This Issue, What if i supply
on Primary side H1-H2 of Single phase (220/0V)(L1=220V
L2=0V)

Answer / debasrit das

i think answer1 is more correct one

Answer / sreekanth p singh

i just want to know wether this test shall be carried out on
a built core with designed no. of turns of L.V windings only
wound on it.....
please help nyone..
i'm just a student in dis field

Answer / manoj

all answers are good but i want to know what interpretation do u make by the results?

Answer / ketan

i am ketan more (be electrical)

magnetic balance test
1) step1 given 400v R&Y PHASE ONLY. THAT TIME B PHASE OPEN
OR NOT CONNECTED SUPPLY

MEASURE VOLTAGE RY & YB & BR
READING IS RY=400V (GIVEN VOLTAGE)
YB= (3/4 RY) VOLTAGE
BR= (1/4 RY) VOLTAGE

THISE READING COME MEANS TRANSFORMER IS OK OR MAGNETIC
BALANCE OF PHASE IS OK

Answer / j.kesavan

austin hai, iam working in field ,any thing problem in
tr ,we are check py side tr give low voltage two phasecheck
sy is good no problem ,py any thing thing short breaker
will trip.py is good we will get sy voltage is good ratio.

How to calculate the slip ring induction motor rotor current and voltage.

1 Answers   Bhel,

Dear Sirs, I am a technical persons.In one of our Electrical Sub- Station, We have installed three numbers of 1250KVA ,11KV/0.415KV Transformer to feed the Factory load. We have found some abnormality. In one of our Transformers the leakeage current from transformer body to earth through earth continuity wire is almost 86 Amp but in other transformer it is (5-10)Amp. where the load current on three phase and neutral are respectively 1360Amp,1400Amp,1370 Amp & 176Amp. So please any technical person help me about the reasons of this situation and how I can rectify the fault. Moreover,I have measured the earth resistance of the Earth continuity wire which is less than 1 Ohm. Thanks Tapas Barua

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