Sizing service eq.

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dave121

Member
Location
Central Wisconsin
I'm a bit confused on sizing service eq. Running 3 phase 480 volt loads with a 240 volt 1 phase service. Job specs. are
75 hp 3 ph. motor at 96 fla, VFD to run motor, 100 kva trans. stepping up 240v to 480v. (per load a 75 kva would be big enough)
96 x 1.73 x 2= 332 amps.1 ph.240 v.
Can the service be sized for the actual load? Does Nec require a 1.73 multiplier when sizing the service eq.?
Real world jobs out there pull 270 amps at the 1 phase 240 volt service with the same eq. plus a phase converter to run other loads. A 400 amp. service would be large enough.
Any references in the code book?
Thanks for your help.
 
jumper

jumper

Senior Member
Location
3 Hr 2 Min from Winged Horses
dave121 said:
I'm a bit confused on sizing service eq. Running 3 phase 480 volt loads with a 240 volt 1 phase service. Job specs. are
75 hp 3 ph. motor at 96 fla, VFD to run motor, 100 kva trans. stepping up 240v to 480v. (per load a 75 kva would be big enough)
96 x 1.73 x 2= 332 amps.1 ph.240 v.
Can the service be sized for the actual load? Does Nec require a 1.73 multiplier when sizing the service eq.?
Real world jobs out there pull 270 amps at the 1 phase 240 volt service with the same eq. plus a phase converter to run other loads. A 400 amp. service would be large enough.
Any references in the code book?
Thanks for your help.
Click to expand...

I do not understand this equation at all.
 
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dave121

Member
Location
Central Wisconsin
I'm sorry, I thought I made it as simple as possible.
How big does the 1 phase 240 volt service need to be to run a 3 phase 460 volt 75 hp. motor using a VFD to run the motor? will be stepping up with a trans from 240 to 480 to the VFD
 
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