hi gents. ive got a possible problem at work.
ive wired a supply from a switchfuse to a new VSD panel. the cable is a 4c 150mm2. from the VSD there is a 3c 150mm2 to a 60kW pump, standard induction motor. ive pulled in the cables as per the cable schedule, and the CPC is a 25mm2 single core earth. this strokes me as small.
Ive got home todayand tried the adiabatic to see if its big enough.
i found on a fuse manufactureres website that for a 60Kw motor, a 250A bs88 fuse is suitable. (it is to be fused).
ive estimated that the Zs of the motor circuit (20m) is going to be about 0.01 ohms. (the water site is fed by its own transformer). i will confirm when i get back on site on thurs.
this gives me a PFC of 39.836 Ka.
the operating time of a fuse with that fault current is 0.1 secs.
vaklue for k is 176.
i dont really understand the I2t of the protective device, so havent reduced the fault current with that in mind.im happy to be educated on this though.
when doing the adiabaicv gives me cable size of 95mm.
can any of you kind gents please verify this for me please, and point out any flaws in my calculation?
im going to speak to the designer about it, but would like some assistance from here too.
thanks,
john
ive wired a supply from a switchfuse to a new VSD panel. the cable is a 4c 150mm2. from the VSD there is a 3c 150mm2 to a 60kW pump, standard induction motor. ive pulled in the cables as per the cable schedule, and the CPC is a 25mm2 single core earth. this strokes me as small.
Ive got home todayand tried the adiabatic to see if its big enough.
i found on a fuse manufactureres website that for a 60Kw motor, a 250A bs88 fuse is suitable. (it is to be fused).
ive estimated that the Zs of the motor circuit (20m) is going to be about 0.01 ohms. (the water site is fed by its own transformer). i will confirm when i get back on site on thurs.
this gives me a PFC of 39.836 Ka.
the operating time of a fuse with that fault current is 0.1 secs.
vaklue for k is 176.
i dont really understand the I2t of the protective device, so havent reduced the fault current with that in mind.im happy to be educated on this though.
when doing the adiabaicv gives me cable size of 95mm.
can any of you kind gents please verify this for me please, and point out any flaws in my calculation?
im going to speak to the designer about it, but would like some assistance from here too.
thanks,
john