3 Phase Motor Amperage
3 Phase Motor Amperage
(OP)
Quick (and probably painfully simple) question:
I have a 3phase, 60Hz, 3HP motor wired up to 460V.
Based on this information alone, is it possible for me to calculate the running aperage? Do I need to assume a power factor to accomplish this? What should that assumption be?
Thanks
I have a 3phase, 60Hz, 3HP motor wired up to 460V.
Based on this information alone, is it possible for me to calculate the running aperage? Do I need to assume a power factor to accomplish this? What should that assumption be?
Thanks





RE: 3 Phase Motor Amperage
3HP Full-Load Current @ 460 Volts = 4.8 Amps
Obviously when running below full load you will be under this value.
If you can get all the information off the nameplate work the following EQ:
Amps=HPx746/VOLTSx%EFFxPFx1.73
or you could estimate efficiency 92% and power factor 80%
This would give you:
Amps=3x746/460x.92x.80x1.73
=3.8
So you would be somewhere between 3.8-4.8 Amps
Obviously the best thing would be to actually take an Ammeter and measure the current.
David Baird
Sr Controls Designer
EET degree.
Journeyman Electrician.
RE: 3 Phase Motor Amperage
thread237-142080
RE: 3 Phase Motor Amperage
Yes you need to know or assume the power factor (PF) and efficiency (EFF) too.
For this size motor assuming it is 4 poles I will give ; PF~0.80 and EFF~0.85
Il = 3*746/(1.732*460*0.85*0.8)= 4.13 amperes
RE: 3 Phase Motor Amperage