Answer Posted / rajukumar sripelli

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....

PLEASE SEND THE PREVIOUS YEARS QUESTION PAPERS OF RRB JUNIOR ENGINEER-ELECTRICAL

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