Answer / pradyumna171

Fourmela No 1 power in one phase/Voltage in one phase(I.e phase voltage)
example there is a 300 KVA 11KV/433 V transfomula. Power in one phase 300KVA/3 =100KVA both in HT & LT side, Phase voltase in HT side 11/√3 = 6351Volt .Phase voltage in LT side 433/√3 = 250 Volt.
According to formula HT side current 100,000/6351 = 15. 7 amps. and LT side current 100,000/250 = 400 amps
Formula No 2 for HT side transformer in kVA/20 and for LT side KVA×4/3. field lineman are using this formula.
According to this formula 300 KVA transformer's HT side current 300/20 =15 amps apporximately +5℅ may added for big size to accurate value. And LT side current 300×4/3 = 400 amps apprx.
In general formula for 300 KVA 11KV/433V transformer HT side current KVA/LV×√3 i.e 300000/11000×1.732 = 15.7 amps .LT side current 300000/433×√3 = 400 amps

PRADYUMNA CHANDRA PANDA
mob No 943
7917849

Answer / haider

P=Root3 *VIcos$
P=KVA rating of DTR
V=primary volage (HV side)
cos$=power factor
Exp:
100KVA DTR
primary volage =11000V
let Power factor=0.97
I=kva/1.732*11000*0.97
I=5A

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