1. What is the Motor Amperage Equation?

The motor amperage equation (I = P/V) calculates the current drawn by an electrical motor based on its power consumption and operating voltage. This fundamental electrical relationship helps in sizing circuit breakers, wiring, and other electrical components.

2. How Does the Calculator Work?

The calculator uses the basic electrical power equation:

Where:

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

Explanation: The equation shows the direct relationship between power and current, and the inverse relationship between voltage and current.

3. Importance of Current Calculation

Details: Proper current calculation is essential for electrical safety, preventing circuit overloads, selecting appropriate wire sizes, and ensuring efficient motor operation.

4. Using the Calculator

Tips: Enter power in watts and voltage in volts. Both values must be positive numbers. For three-phase motors, use line-to-line voltage and total power.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between real power and apparent power?
A: This calculator uses real power (watts). For AC motors with power factor considerations, apparent power (VA) may be needed.

Q2: How does efficiency affect the calculation?
A: The basic equation assumes 100% efficiency. For more accurate results, divide by motor efficiency (as a decimal).

Q3: What about three-phase motors?
A: For three-phase, the equation becomes \( I = \frac{P}{\sqrt{3} \times V \times PF \times Eff} \) where PF is power factor and Eff is efficiency.

Q4: Why is my actual measured current different?
A: Startup currents (inrush) can be 5-7 times higher than running current. Motors also draw more current under load.

Q5: What safety margin should I add?
A: Standard practice is to size conductors and breakers at 125% of full-load current for continuous duty motors.