Motor FLC Calculator: Find Amps from HP and Voltage

Single‑Phase Motor

I_FLC = (HP × 746) / (V × η × PF)

Three‑Phase Motor

I_FLC = (HP × 746) / (√3 × V × η × PF)

Where：

• I_FLC：The steady-state input current (line current) drawn by a single-phase AC motor when operating at its rated voltage, rated power, and rated load.
  

• HP：The rated mechanical shaft output power of the motor, which represents the load power the motor is capable of driving.

• η：The ability of the motor to convert input electrical power into output mechanical power, reflecting the magnitude of energy losses (including copper losses, iron losses, mechanical losses, etc.).

• PF：A parameter that reflects the phase difference between the voltage and current waveforms in an AC circuit, equal to the ratio of active power to apparent power.

Based on NEC 2023 Tables 430.247–430.250, this tool calculates the Full-Load Current (FLC) for motors under various voltages and power ratings, used for circuit breaker, fuse, and conductor sizing.

Input motor parameters to automatically retrieve NEC standard values:

• Supports single-, two-, and three-phase systems

• Supports HP and kW inputs

• Real-time FLC calculation (A)

• Compliant with NEC 2023

Key Formula

NEC FLC = Look-up value from tables

Example:
- Single-phase 240V, 1HP → FLC = 4.0 A
- Three-phase 480V, 1HP → FLC = 2.7 A

Important Notes

• NEC FLC is typically higher than nameplate current

• Must be used for protective device sizing

• Not applicable to VFD-driven motors

• Voltage must be standard