Answer / laxmikanta sasmal

COZ ALTERNATOR ARE GENERALLY STAR CONNECTED WHEREAS THREE LEADS ARE SHORTED AND OTHER THREE LEADS ARE OUT,THEN CONNECTED TO DELTA/DELTA OR DELTA/STAR CONNECTED TRANSFORMER'S DELTA END.DELTA CONNECTION WINDING IS MANDATORY AT ALTERNATOR OUTPUT SIDE.BECOZ IN SAME VOLTAGE LEVEL TWO STAR POINT IS NOT ALLOWED.IT WILL CAUSE OF HUGE AMOUNT CIRCULATING CURRENT FLOWING IN UNINTENDED PATH AT THE TIME OF FAULT/UNBALANCE AND MALFUNCTIONING OF PROTECTION RELAYS

Answer / raghavendran.r

I believe that it has got something to do with neutralizing of Zero Sequence components in the power system arising during unbalanced condition.
In star, the zero sequence current flows from the neutral to the phases during unbalanced condition.Where as the Zero seq currents wont be able to circulate in Delta connection as it would get cancelled out.
So I suppose that it could be the reason behind such kind of an arrangement.
But do confirm this answer with any other reference.

Answer / satendra

If we connect the output of alternator to star side then the resultant voltage will be 3^.5 times of the real voltage.
So now we have to handle more voltage.
In order to avoid this condition we use delta connection.

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