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HP times 746, divided by efficiency, then divided by voltage. Example, for a 460V, 10 HP motor with an efficiency of 85%: { (10 HP) x (746 Watts/HP) } / { .85 efficiency) x (460V) } = 19.08 amps. If you are looking for a basis for sizing conductors, then look up this same motor in NEC Table 430.150, and you get 14 amps.
Calculate Horsepower from Full Load Amps. Note: Most motors are rated using "Peak HP consumed" which is much higher than "true continuous HP".
what are the full load amps on a 700hp motor 3 phase 480 VAC? Re: 700 hp motor It's beyond the range of the NEC table. You would have to get that information from the manufacturer. I would estimate that the current would be on the order of 790 amps.
Table 430.248 tells me a 5 HP motor draws 28 amps Table 430.52 tells me the max Short-Circuit protection is 250% of 28 amps or 70 amps max breaker Table 310.16 tells me #12 can handle 25 - 30 amps depending on the insulation. I know I can size the breaker more that the current carrying capability of the wire for a motor.
I have a 5HP 183 frame 5 HP motor that pulls 48A at 240 V rms, so it all depends on the load. If that makes you wonder; yes, a 5HP motor (25 A nameplate) can pull 48 Amps and drive a 10 HP pressure washer load. You just need to put a big fan on it to keep it from overheating. This example has a ducted 1400 CFM airflow thru it.
What is the purpose of knowing locked-rotor current values of a motor? For example: Lets say I have a 25 hp, 460V code A motor. 25 x 3.14 = 78.5 x 1000 / 460 / 1.732 = 98.5 amperes of locked-rotor current. What does this tell me? Say I am using a typical inverse-time breaker. FLC is...
Per NEC section 430.62, the first thing you need to figure out is the largest breaker that would be permitted for the largest motor. For an inverse-time circuit breaker serving the 20 horsepower motor, this would be 27 amps x 2.5 = 67.5 amps, rounded up to 70 amps (see NEC section 430.52(C)(1)).
It's really sort of a rhetorical question. Practically speaking, it is easy enough to set down safe circuit requirements for it although at 600 HP, you could easily end up running wire a size bigger than you need. If you have to guess and you look at the NEC tables for motors up to 500 HP, you have to guess about 700 amps for a 600 HP motor.
In the last two types, the higher speed should still read higher amps than the lower speed, but if the CTs are in the wrong place, you might only be reading a portion of the current. In the Constant HP configuration, the higher speed means less torque for the HP to remain the same, so less torque means less current.
5 HP 460 Volt = 7.6 A OCPD 7.6A X 175% = 13.3 A (Minimum size) Round this up to the next standard fuse = 15 Amps (Standard size) 7.6A X 225% = 17.1 A (Maximum size) Round Down for the standard size fuse = 15 Amps In this case both the standard size and the maximum would be the same size. Overload 7.6 A X 115% = 8.74 Round down and start with a ...