1. Basic Motor Power Formula

The fundamental formula for DC motor power calculation is:

Where:

• \( P \) — Power in watts (W)
• \( V \) — Voltage in volts (V)
• \( I \) — Current in amperes (A)

2. Other Common Motor Formulas

Torque Formula: \[ \tau = \frac{P \times 60}{2 \pi \times RPM} \] Where \( \tau \) is torque in Newton-meters (Nm) and RPM is revolutions per minute.

Efficiency Formula: \[ \eta = \frac{P_{out}}{P_{in}} \times 100\% \] Where \( \eta \) is efficiency in percentage.

Three-Phase Power Formula: \[ P = \sqrt{3} \times V \times I \times PF \] Where PF is power factor (0 to 1).

3. Practical Applications

Motor Sizing: Calculate power requirements to select appropriate motor size.

Energy Consumption: Estimate power usage for cost calculations.

Performance Analysis: Evaluate motor efficiency and performance characteristics.

4. Using the Calculator

Tips: Enter any two known values to calculate the third. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between DC and AC motor calculations?
A: DC motors use simple P=VI, while AC motors require power factor consideration (P=VI×PF for single-phase, P=√3×VI×PF for three-phase).

Q2: How do I account for motor efficiency?
A: Divide output power by efficiency to get input power requirements.

Q3: What is typical motor efficiency?
A: Ranges from 70% for small motors to over 95% for large premium efficiency motors.

Q4: How does voltage affect motor performance?
A: Higher voltage typically allows lower current for same power, reducing I²R losses.

Q5: What safety factors should I consider?
A: Add 20-30% margin to calculated power requirements for start-up currents and load variations.