HP to Amps Calculator

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DC motors need only voltage and efficiency. AC motors also need a power factor.
The rated output power on the motor nameplate in mechanical horsepower (1 HP = 746 W).
HP
Line-to-line voltage for three-phase motors; line-to-neutral (or supply) voltage for single-phase and DC.
V
Ratio of mechanical output power to electrical input power, as a percentage. Found on the motor nameplate; 85-95% is typical for modern motors.
%
Ratio of real power to apparent power (0 to 1). Induction motors are typically 0.80-0.90 at full load.
Full-load current
6.12A

Current drawn at rated horsepower output

Electrical input power4,144.4W
Mechanical output power3,730W
Motor power loss414.4W
Apparent power (kVA)4.876kVA
Mechanical output (W)3,730
Power loss / heat (W)414.4

A 5 HP three-phase AC motor at 460 V draws about 6.12 A.

  • For continuous motor loads, the NEC requires conductors and overcurrent protection sized at 125% of full-load current: 7.6 A minimum.
  • An efficiency of 90% is typical for a modern induction motor at full load.
  • A power factor of 0.85 is reasonable for an induction motor at full load.

Next stepUse this full-load current to size your wire gauge (AWG), circuit breaker, and motor starter. Always add the 125% safety margin required by NEC Article 430.

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