Motor Power Calculator

Understanding Electric Motor Power

Electric motors convert electrical power to mechanical power. The relationship involves motor efficiency (η), which accounts for losses in windings, bearings, and core. A 90% efficient motor converting 1kW electrical input delivers 900W of mechanical output.

Motor Power Formulas

Electrical Input Power (W) = V × I × PF (single phase AC) Electrical Input Power (W) = √3 × V × I × PF (three phase AC) Mechanical Output Power (W) = Electrical Input × Efficiency Shaft Power (kW) = Torque (N·m) × Speed (rpm) × 2π / 60,000

How to Use This Calculator

Enter supply voltage, current, power factor, and efficiency. Or enter torque and speed for mechanical output. The calculator gives input power, output power, and power loss as heat.

Practical Examples

Example 1: Three-phase motor, 400V, 10A, PF 0.85, efficiency 92%. Input = √3 × 400 × 10 × 0.85 = 5,888W. Output = 5,888 × 0.92 = 5,417W ≈ 5.4kW.

Example 2: Motor with 50 N·m torque at 1,450 rpm. Power = 50 × 1,450 × 2π / 60,000 = 7,592W ≈ 7.6kW.

Motor Efficiency Standards

Modern motors must meet IE efficiency standards:

• IE1: Standard efficiency (~75–80%)
• IE2: High efficiency (~81–87%)
• IE3: Premium efficiency (~88–93%)
• IE4: Super premium efficiency (>93%)