1. What is an Electric Motor Sizing Calculator?

Definition: This calculator determines the required horsepower (HP) of an electric motor based on either mechanical parameters (torque and RPM) or electrical parameters (voltage, current, efficiency, and power factor).

Purpose: It helps engineers, technicians, and DIYers properly size electric motors for various applications.

2. How Does the Calculator Work?

The calculator uses two fundamental formulas:

Where:

• \( HP \) — Horsepower
• \( T \) — Torque (lb-ft)
• \( RPM \) — Revolutions per minute
• \( V \) — Voltage (volts)
• \( I \) — Current (amps)
• \( \eta \) — Motor efficiency (0-1)
• \( PF \) — Power factor (0-1)

Explanation: The mechanical formula converts rotational power to HP, while the electrical formula converts electrical power to mechanical HP accounting for losses.

3. Importance of Proper Motor Sizing

Details: Correct motor sizing ensures efficient operation, prevents overheating, and matches the load requirements while optimizing energy consumption.

4. Using the Calculator

Tips: Choose calculation method (mechanical or electrical) and enter the required parameters. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Which method should I use?
A: Use mechanical if you know torque/RPM requirements. Use electrical if you're sizing based on power supply characteristics.

Q2: What's a typical motor efficiency?
A: Standard motors are typically 85-95% efficient (η = 0.85-0.95).

Q3: What is power factor?
A: PF represents the ratio of real power to apparent power, typically 0.8-0.95 for AC motors.

Q4: Why 5252 in the mechanical formula?
A: This constant comes from unit conversion (1 HP = 550 ft-lb/sec and 1 RPM = 2π rad/min).

Q5: Should I add a safety factor?
A: Yes, typically add 10-20% to the calculated HP for safety margin and startup conditions.