450 HP Motor Amps — Full-Load Current, Wire & Breaker Size
Full-load current of a 450 horsepower motor at every standard voltage, with minimum conductor size and maximum breaker and fuse ratings worked out for each.
A 450 HP motor draws 515 A at 460 V and 412 A at 575 V three-phase.
450 HP three-phase motor
| Voltage | Full-load amps | Conductor ampacity (125%) | Min. copper wire, 75°C | Max. inverse-time breaker (250%) | Max. time-delay fuse (175%) |
|---|---|---|---|---|---|
| 460 V | 515 A | 643.8 A | 1750 kcmil | 1600 A | 1000 A |
| 575 V | 412 A | 515.0 A | 900 kcmil | 1200 A | 800 A |
| 2300 V | 103 A | 128.8 A | 1 AWG | 300 A | 200 A |
450 HP is 335.70 kW of shaft output. Wire sizes above are the smallest copper conductor whose 75°C ampacity covers 125% of full-load current; 14 AWG is the practical minimum for power circuits. They do not include voltage drop — on long runs check the voltage drop calculator — or derating for hot locations or crowded conduits. Breaker and fuse values are maximums with the next-standard-size-up allowance applied; smaller devices are fine if the motor starts without tripping.
Motor wire & breaker size calculator
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Other horsepower ratings
- 1/6 HP
- 1/4 HP
- 1/3 HP
- 1/2 HP
- 3/4 HP
- 1 HP
- 1 1/2 HP
- 2 HP
- 3 HP
- 5 HP
- 7 1/2 HP
- 10 HP
- 15 HP
- 20 HP
- 25 HP
- 30 HP
- 40 HP
- 50 HP
- 60 HP
- 75 HP
- 100 HP
- 125 HP
- 150 HP
- 200 HP
- 250 HP
- 300 HP
- 350 HP
- 400 HP
- 450 HP
- 500 HP
Frequently asked questions
How many amps does a 450 HP motor draw?
A 450 HP motor draws 515 A at 460 V and 412 A at 575 V three-phase. These are the code table values used for circuit sizing; the actual nameplate current is usually a little lower.
What size wire and breaker for a 450 HP three-phase motor at 460 V?
Full-load current is 515 A, so conductors need at least 643.8 A of ampacity: 1750 kcmil copper at 75°C. The inverse-time breaker may be up to 1600 A and a dual-element time-delay fuse up to 1000 A.
NECTables.com is an independent reference and is not affiliated with, endorsed by, or a substitute for the National Fire Protection Association (NFPA). NEC® and National Electrical Code® are registered trademarks of the NFPA. Values shown are commonly published engineering data and independent calculations based on the methods of NFPA 70; they are not a reproduction of the Code. Always confirm against the edition adopted in your jurisdiction, including local amendments, and consult a licensed electrician or engineer before doing electrical work.