ALLInterview.com :: Home Page            
 Advertise your Business Here     
Browse  |   Placement Papers  |   Company  |   Code Snippets  |   Certifications  |   Visa Questions
Post Question  |   Post Answer  |   My Panel  |   Search  |   Articles  |   Topics  |   ERRORS new
   Refer this Site  Refer This Site to Your Friends  Site Map  Bookmark this Site  Set it as your HomePage  Contact Us     Login  |  Sign Up                      
tip   To Refer this Site to Your Friends   Click Here
Google
   
 
Categories  >>  Engineering  >>  Electrical Engineering
 
 


  

 
 Civil Engineering interview questions  Civil Engineering Interview Questions
 Mechanical Engineering interview questions  Mechanical Engineering Interview Questions
 Electrical Engineering interview questions  Electrical Engineering Interview Questions
 Electronics Communications interview questions  Electronics Communications Interview Questions
 Chemical Engineering interview questions  Chemical Engineering Interview Questions
 Aeronautical Engineering interview questions  Aeronautical Engineering Interview Questions
 Bio Engineering interview questions  Bio Engineering Interview Questions
 Metallurgy interview questions  Metallurgy Interview Questions
 Industrial Engineering interview questions  Industrial Engineering Interview Questions
 Instrumentation interview questions  Instrumentation Interview Questions
 Automobile Engineering interview questions  Automobile Engineering Interview Questions
 Mechatronics Engineering interview questions  Mechatronics Engineering Interview Questions
 Marine Engineering interview questions  Marine Engineering Interview Questions
 Power Plant Engineering interview questions  Power Plant Engineering Interview Questions
 Engineering AllOther interview questions  Engineering AllOther Interview Questions
Question 
What core magnetic balance test of transformer?
How to do this test in a three phase Star delta (star-LV, 
Delta-HV) transformer?
How to measure and where to measure?

thanks and regards
Austin
 Question Submitted By :: Austin
I also faced this Question!!     Rank Answer Posted By  
 
  Re: What core magnetic balance test of transformer? How to do this test in a three phase Star delta (star-LV, Delta-HV) transformer? How to measure and where to measure? thanks and regards Austin
Answer
# 1		 This is nothing but voltage ratio test, To find available
voltage for the small test voltage applied on secondary 
Is This Answer Correct ?    14 Yes 141 No
Mustafa
 
  Re: What core magnetic balance test of transformer? How to do this test in a three phase Star delta (star-LV, Delta-HV) transformer? How to measure and where to measure? thanks and regards Austin
Answer
# 2		 MAGNETIC BALANCE TEST

THIS TEST IS SIMILAR AS OPEN CIRCUIT TEST

PROVIDE THE SINGLE PHASE SUPPLY (BELOW 230 V)TO THE STAR
SIDE OF THE TRANSFORMER BY PROPERLY CONNECTED

1.GIVE SUPPLY TO 2N AND 2U AND THEN MEASURE THE VOLTAGE ON
2N2V AND 2N2W
(i.e)IT SATISFIED THE CONDITION

2U2N=2V2N+2W2N

SIMILARILY THE TEST CONDUCTED ON OTHER TWO PHASES BY SAME
MEANS

(NOTE: NO ONE SHOULD BE STAND ON HIGH VOLTAGE SIDE WHILE
TESTING ) 
Is This Answer Correct ?    90 Yes 31 No
E.saravanan
 
 
 
  Re: What core magnetic balance test of transformer? How to do this test in a three phase Star delta (star-LV, Delta-HV) transformer? How to measure and where to measure? thanks and regards Austin
Answer
# 3		 Provide 2-phase supply on the HV side of transformer on two
phases.
Then measure magnetizing current in the supplied phases.
Then measure the voltages on the LV side.
Repeat the same for the other phases and measure current
and LV corresponding voltages.

The LV voltages should obey

ry = rb+by
and
rn = bn+yn 
Is This Answer Correct ?    37 Yes 21 No
Mugaisi
 
  Re: What core magnetic balance test of transformer? How to do this test in a three phase Star delta (star-LV, Delta-HV) transformer? How to measure and where to measure? thanks and regards Austin
Answer
# 4		 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. 
Is This Answer Correct ?    5 Yes 25 No
J.kesavan
 
  Re: What core magnetic balance test of transformer? How to do this test in a three phase Star delta (star-LV, Delta-HV) transformer? How to measure and where to measure? thanks and regards Austin
Answer
# 5		 HI ,
this is rajukumar sripelli from REPUTED TRANSFORMER
MANUFACTURING COMPANY ..testing department ..


AS u all above is not fully correct....

Magnetic balance test is done on TRANSFORMER to see whether
the transformer core is magnetically balanced or
not...AND ALSO WINDING CONDITION....IN FAULT CONDITION DUE
TO HIGH CURRENTS WINDING MAY BE DAMAGE....

for example
we r having delta HV and star winding LV side ...

HV SIDE WE WIL BE HAVING THREE BUSHINGS....THOSE R 1U,1V,1W..
HV SIDE WE WIL BE HAVING FOUR BUSHINGS.....2U,2V,2W,2N...

WE CAN DO THIS MBT (MAGNETIC BALANCE TEST)WITH 1PHASE
SUPPLY(1PHASE AND NEUTRAL(230V)) OR WITH 2-PHASE
SUPPLY(2-PHASES(440V))

1ST STEP OF MBT: GIVE POWER SUPPLY 1-PHASE OR 2 PHASE
BETWEEN 1U AND 1V ,MEASURE THE VOLTAGES BETWEEN 1V-1W AND
1U-1W AND ALSO 2U-2N,2V-2N,2W-2N..

SO HERE IF THE CORE IS CORRECTLY BALANCED THEN WE WILL GET
RESULTS AS FOLLOWS


1U-1V 1V-1W 1U-1W 2U-2N 2V-2N 2W-2N
440 300 140 90 50 40



THAT MEANS HV SIDE : 1U-1V = 1V-1W + 1U-1W
I.E 440V = 300 + 140

AND ALSO LV SIDE : 2U-2N = 2V-2N + 2W-2N

90 = 50 + 40

STEP 2: AFTER DOING THIS ..INTERCHANGE THE CONNECTIONS
BETWEEN 1V-1W AND MEASURE THE VALUES AS ABOVE...

STEP 3: AFTER DOING THIS ..INTER CHANGE THE CONNECTIONS
BETWEEN 1U-1W AND MEASURE THE VALUES AS ABOVE...
IF ANY FAULT IS THERE IN TRANSFORMER WE CAN NOT FIND GOOD
RESULTS....
IF THE WINDING IS DAMAGED .... WE WILL GET ZERO VALUES ....

ex: HV SIDE 1U-1V = 1V-1W + 1U-1W
440V = 440 + 0

AND ALSO LV SIDE : 2U-2N = 2V-2N + 2W-2N

90 = 90 + 0
THIS IS THE ACTUAL APPLICATION OF MANGNETICA BALANCE TEST...


THANKS.... 
Is This Answer Correct ?    211 Yes 6 No
Rajukumar Sripelli
 
  Re: What core magnetic balance test of transformer? How to do this test in a three phase Star delta (star-LV, Delta-HV) transformer? How to measure and where to measure? thanks and regards Austin
Answer
# 6		 Hi,
You may use either single-pase on the star side of the
transformer as in Answer #2 or apply two line voltages i.e.
apply 415V on A and B terminals on the HV-side of the
transformer and follow the steps of Rajukumar Sripelli in
Answer #5. 
Is This Answer Correct ?    5 Yes 2 No
Engr. L.o. Osuji
 
  Re: What core magnetic balance test of transformer? How to do this test in a three phase Star delta (star-LV, Delta-HV) transformer? How to measure and where to measure? thanks and regards Austin
Answer
# 7		 all anser are right 
Is This Answer Correct ?    0 Yes 24 No
Dheerendra Singh
 
  Re: What core magnetic balance test of transformer? How to do this test in a three phase Star delta (star-LV, Delta-HV) transformer? How to measure and where to measure? thanks and regards Austin
Answer
# 8		 all answers are good but i want to know what interpretation do u make by the results? 
Is This Answer Correct ?    1 Yes 7 No
Manoj
 
  Re: What core magnetic balance test of transformer? How to do this test in a three phase Star delta (star-LV, Delta-HV) transformer? How to measure and where to measure? thanks and regards Austin
Answer
# 9		 Answer #5 is fine.. but i want to add something more..
normally this test is made in star side of the transformer.
the result should be varified like following:
1) if 2u-2n is fed by 230 volt.
- the nearest phase (2v-2n) will experience the 85% to 90%
of fed voltage at 2u-2n. (i mean 2v-2n = 195.5 to 207
volt). And the distant phase (2w-2n) will experience the
10% to 15% of fed voltage at 2u-2n. (i mean 2w-2n = 23 to
34.5 volt).
2) if 2v-2n is fed by 230 volt.
- then the fed pahase is middle phase, and both other phase
are magnetically in equal distance.. so the measured
voltages in 2u-2n or 2w-2n = 50 % (or 40 to 60 % is also
accaptable). so the 2u-2n or 2w-2n = 92v to 138v is
accaptable.
3) if 2w-2n is fed by 230 volt.
- the nearest phase (2v-2n) will experience the 85% to 90%
of fed voltage at 2w-2n. (i mean 2v-2n = 195.5 to 207
volt). And the distant phase (2u-2n) will experience the
10% to 15% of fed voltage at 2u-2n. (i mean 2w-2n = 23 to
34.5 volt).

*If the results are found beyond these above mentioned
limits then other tests (like open ckt test with rated
voltage) should be performed to be sure about core and
winding.
*You can measure and note down the current of each injected
phase. it will give u a signaficant idea about winding. if
the winding has an inter-tern short then the faulty phase
will draw comapretively large magnetizing current like 3A
or 5A, wheather other phases will draw 60mA to 100mA.
*Remember, the magnetic reluctance path of a core is not
lenier, so the result veries itself. But big differences
are remarkable.
*Sometime due to non-lenier characteristic of magnatic
circuit and the presense of harmonics in the fluxes of un-
excited phases, the algebric sum of induced volage in two
phases may not be equal to the applied voltage.
*if there is a turn to turn fault in any phase winding, the
faulty section will draw comparetively large magnatizing
current which will oppose the magnetic fluxes and will
result a very low induced voltage (tends to zero) in the
faulty phase.
*this test should be performed after demagnaizing the
transformer properly. slightly magnatized transformer (like
after insulation test) can give you an unexpacted and
distorted result of magnetic balance test. 
Is This Answer Correct ?    48 Yes 3 No
Engr. Ziaul Ashraf Shafi
 
  Re: What core magnetic balance test of transformer? How to do this test in a three phase Star delta (star-LV, Delta-HV) transformer? How to measure and where to measure? thanks and regards Austin
Answer
# 10		 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 
Is This Answer Correct ?    6 Yes 11 No
Ketan
 

12 >>

 
 
 
Other Electrical Engineering Interview Questions
 
  Question Asked @ Answers
 
america 60hz electric supply is used; but india it is 50hz; why? and if we use 60 hz supply what changeg has to be done or all the equipment has to be thrown which has rating of 50hz frequincy  1
What is Transformer? HSL23
What are pre paid energy meters ? How it works ? Siemens1
how we can calculate earth fault current? Alchemist1
What is meant rectifiers.. MTS1
AT THE TIME OF INSTALLING THE POWER PLANT POWER IS TAKEN FROM NEARBY GRID AND GIVING THE SUPPLY TO THE GENERATOR WHICH ACTS AS MOTOR. WHAT IS THE NEED OF RUNNING THE GENERATOR AS MOTOR?  6
now a shunt motor is practically a constant speed motor , then how does it meet the increase or decrease in the load ?  1
Form fator is the ratio of?  5
how does an open delta transformer works  1
why do we have another cartridge filled with oil fitted at the bottom silica gel cartridge in power transforers  1
What will be the minimum megger value of 1700 KVA Transformer? a) Do megger value varies according to climate conditions and area . b) If megger value is 100 mega ohm is it good for new transfomer. Explain?  3
what is a circuit breaker. Weite the types of circuit breaker.  4
 
For more Electrical Engineering Interview Questions Click Here 
 
 
 
 
 


   
Copyright Policy  |  Terms of Service  |  Help  |  Site Map 1  |  Articles  |  Site Map  |   Site Map  |  Contact Us |   interview questions urls   External Links 
   
Copyright © 2012  ALLInterview.com.  All Rights Reserved.

ALLInterview.com   ::  Forum9.com   ::  KalAajKal.com