How to Calculate Electric Motor Horsepower

The Electric Motor Horsepower Calculator computes the power for AC motors in HP, kW, and W based on amps, voltage, power factor, efficiency, and phase type. The formulas used are:

Single-Phase AC Motor (Watts):

Three-Phase AC Motor (Watts):

Horsepower (HP):

Kilowatts (kW):

Where:

• \( HP \): Horsepower.
• \( kW \): Kilowatts.
• \( W \): Watts.
• \( I \): Amps (A).
• \( V \): Voltage (Volts).
• \( \eta \): Motor efficiency as a decimal (e.g., 0.85 for 85%).
• \( \cos \phi \): Motor power factor as a decimal (e.g., 0.8 for 80%).
• 746: Conversion factor from watts to HP.
• 1000: Conversion factor from watts to kW.

Enter the amps, voltage, power factor, efficiency, and phase type to calculate the power in HP, kW, and W.

Using the Electric Motor Horsepower Calculator

This calculator is useful for electrical engineers and technicians to determine the power of AC motors from measured current and other parameters in multiple units.

Input the amps, voltage, power factor (default: 0.8), efficiency (default: 0.85), and phase type. The calculator outputs the power in HP, kW, and W.

Example: Calculate power for a single-phase AC motor with 23.860 A at 230 V, 0.85 efficiency, and 0.8 power factor.

1. Amps: \( 23.860 \, \text{A} \)
2. Voltage: \( 230 \, \text{V} \)
3. Calculation: \( W = 23.860 \times 230 \times 0.8 \times 0.85 = 3731.000 \, \text{W} \)
4. Then: \( HP = \frac{3731}{746} = 5.000 \, \text{HP} \)
5. Then: \( kW = \frac{3731}{1000} = 3.731 \, \text{kW} \)
6. Result: \( 5.000 \, \text{HP}, 3.731 \, \text{kW}, 3731.000 \, \text{W} \)

Use this tool for precise motor power calculations in design and maintenance.

Common FAQ

Below are frequently asked questions about Electric Motor Horsepower calculations:

• Q: What is the difference between single-phase and three-phase calculations?
  A: Three-phase uses a √3 factor to account for the phase distribution, resulting in higher power for the same amps compared to single-phase.
• Q: Why include efficiency and power factor?
  A: Efficiency adjusts for real-world losses, and power factor accounts for the phase difference in AC systems.
• Q: How accurate is this calculator?
  A: It uses standard formulas with precise conversion factors, providing results rounded to 3 decimal places.
• Q: Can I use this for DC motors?
  A: No, this calculator is for AC motors only; DC motors do not use power factor.
• Q: What if power factor or efficiency is unknown?
  A: Use typical values (0.8 for PF, 0.85 for η) or consult motor nameplate data.