Answer / nadeem

B.delta-delta to star-delta not possible parallel
operation.
C.star-star to delta-delta that is possible parallel
operation.
D.delta-star to star-delta also that is possible parallel
operation.
A.delta-delta to delta-star not possible parallel operation
but im not conferm.

Answer / ravi

For parallel operation of transformers as you know the
requirements, 1. magnitude of the voltage, 2. phase angle
difference between the i/p and o/p voltages, 3. equal
percentage impedance of the transformers.

I don't think that whatever you are asked configurations
same vector symbol will get. So we can't do paralleling.
if you get the same phase angle difference ypu can go ahead
with paralleling.

Answer / vikas tomar

If the transformers are star-star or delta-delta, they can
not be paralleled with star-delta or delta-star,As there
will be the phase difference of 30 degree b/w the secondary
voltages for the same supply voltages across the primaries
of the two transformers.It will result the circulating
current in transformer windings.
Hence option (d)is correct answer.

Answer / sourabh

A)delta-delta or delta star is possible

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