1. What is a Generator Sizing Calculator for Motor Loads?

Definition: This calculator estimates the required generator power (in kW) needed to start and run electric motors based on motor horsepower, efficiency, and power factor.

Purpose: It helps electrical engineers, contractors, and facility managers properly size generators for motor-driven equipment.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( P_e \) — Generator power required (kW)
• \( HP \) — Motor horsepower
• \( \eta \) — Motor efficiency (typically 0.7-0.95)
• \( PF \) — Power factor (typically 0.7-0.9)

Explanation: The formula converts horsepower to watts (746W = 1HP), then accounts for motor efficiency and power factor to determine the actual generator capacity needed.

3. Importance of Proper Generator Sizing

Details: Correct generator sizing prevents underpowered situations (which can damage equipment) and avoids oversizing (which increases costs and reduces efficiency).

4. Using the Calculator

Tips: Enter the motor horsepower, efficiency (default 0.85), and power factor (default 0.8). All values must be > 0. Efficiency and PF must be between 0 and 1.

5. Frequently Asked Questions (FAQ)

Q1: Why is motor efficiency important?
A: Efficiency accounts for energy losses in the motor. Lower efficiency motors require more generator capacity.

Q2: What is power factor and why does it matter?
A: Power factor represents the ratio of real power to apparent power. Lower PF means more generator capacity is needed for the same real power.

Q3: Does this include startup current?
A: No, this calculates running power. For startup, multiply the result by 3-5x for most motors.

Q4: What's a typical efficiency for electric motors?
A: Standard efficiency motors are 85-90%, premium efficiency 90-95%, and older motors may be 70-85%.

Q5: How do I find my motor's power factor?
A: Check motor specifications or use 0.8 as a default for most induction motors at full load.