Question { MEIL, 411739 }

I want formula to calculate cable size as per load given in
kw & amp.I searched many sites but didn't right answer.Plz
reply me asap.

Answer

hai am also no exact answer
may be
eg 5HP motor select cable size 2.5sqmm cu cable, r 4 sqmm
Al cable.
work out
5Hp motor taken 90% full load current 7 amps.
that current * 5 times = 35 Amps (motor not run in full load
its my experiance)
2.5sqmm cu cable full load withstand current 36A
4sqmm Al cable full load with stand current 34A
so we choice Cu r Al cable

Question { Cipla, 5487 }

if 2500 KVA TRANSFORMER CAPACITY.33KV INCOMING HOW ARE
AMPEAR PRIMERY SAID

Answer

Formula is KVA/ 1.732* volt

2500*1000/1.732*33*1000
2500/1.732*33
43.73A

Question { 3619 }

What is the reason of using bus-bars on the secondary on the
LT transformers?

Answer

hi friends, this question is most important one for all interview. ans is HT side voltage is high so current is low but LT transformer secondary voltage is low current is high,so we are not connected more cables in TB side so we are using bus bar. its formula is KVA/1.732* volage(HT OR LT)