We use in star connection in seconday connection becouse
need neutal point in load sied( some load supply need 3
phase and some need single phase)but it is remember that
only star connection use in distrubution side transformer.
Nuetral in used in single phase system and 3 phase 4 wire
systeme due to we star connection in secondory. in primary
used 3 phase system.but suresh kumar why not convert
voltage from 400v to 33kv.p/s explain the reason.
For distribution transformers, loads are connected to
secondry side. hence, requirement of neutral can be
obtained by connecting secondry of the transformer in star.
Secondly, to reduce or minimise the third harmonics in the
transformers, primary side connection generally done in
in secondary side there is a chance for single phase load,
three phase load, if its single phase load added more there
is a chance for unequal voltage in each phases. here we
need one neutral point that is refered as a reference
potential for load equalise the phase voltages
WE USE DELTA CONNECTION AT PRIMARY AND STAR CONNECTION AT
SECONDARY IN CASE IF STEP UP OF VOLTAGE REQUIREMENT BECAUSE
IN DELTA/STAR TRANSFORMER THE OUT PUT VOLTAGE WILL BE 1.413
TIMES HIGHER THAN THE PHASE VOLTAGE EVEN WHEN BOTH HAVING
SAME NUMBER OF TURN. SO THE SECONDARY WILL REQUIRE LESS
we should use delta connection in primary and star to
secondary because in delta line voltage = pphase voltage
and instar line voltage = 1.732phase voltage hence we get
173.2% more voltage hence we use delta star transformer.