Assume PF of transformer is .8.
rating of transformer=1500kVA=1500X.8=1200kW
So that maximum current-
So cable size required if copper cable
1mm=4amp= 400sqmm(by consedering all factors)
For aluminium cable
First calculate the current of primary side(HT) and derate the cable by atleast 0.7.
Current I after Derating =78.73/.7 =112A (0.7 if laid on the trays or value will vary if buried in the ground).
Cable equivalent to rating has to be selected.
Now Short circuit withstand capacity (sq. of I X t in sec) has to be checked from the cable catalogue.This value of cable should be higher then SC withstand capacity of the ground usually it is 50KA.it less go for next size and finalise.
when an induction motor runs on load.at that time if we
reduce the supply voltage the current increases.But when it
runs without load,if we reduce the supply voltage the
current also reduced.why?.i checked it practically also.
hi i am aziz electrical associate engineer. i am faceing
problem in acs800 vvvf drive.it is tripping wothout any
alarm/fault.i cheaked all parameters and fault function of
drive, all are correct as well as communication
parameters.but still it is tripping (drive is tripping in
running position not in starting)