Answer Posted / maheshreddy

Purpose: The Polarity and Phase relation tests are
importent when two or more transformer are to be
paralleled.Parelleled transformer must have the same
polarity and phase relation to avoid parial or complete
short circuits.

Test Procedure:(Yyn11)
The L.V. vector will be superimposed on H.V. by connecting
1U & 2U Terminals. The three-phase voltage will be applied
to the line terminals of H.V. winding. Voltage measurement
will be done across:
1U-1V:
1V-1W:
1W-1U:

1V-2V: 1V-2W:
1W-2V: 1W-2W:
1U-2N: 1V-2N:



Checks: - 1V-2V = 1V-2W
1W-2V > 1W-2W
1U-2N + 1V-2N = 1U-1V

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