1. What is the Motor Current Formula?

The single-phase motor current formula calculates the electrical current drawn by a motor based on its power rating, supply voltage, power factor, and efficiency. This calculation is essential for proper circuit sizing and protection.

2. How Does the Calculator Work?

The calculator uses the single-phase motor current formula:

Where:

• \( I \) — Current in amperes (A)
• \( P \) — Power in watts (W)
• \( V \) — Voltage in volts (V)
• \( PF \) — Power factor (unitless, 0-1)
• \( \eta \) — Efficiency (unitless, 0-1)

Explanation: The formula accounts for both the power factor (ratio of real power to apparent power) and motor efficiency to determine the actual current draw.

3. Importance of Current Calculation

Details: Accurate current calculation is crucial for selecting proper wire sizes, circuit breakers, and overload protection devices to ensure safe operation and prevent equipment damage.

4. Using the Calculator

Tips: Enter power in watts, voltage in volts, power factor (typically 0.8-0.95 for motors), and efficiency (typically 0.8-0.95). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical power factor for motors?
A: Induction motors typically have power factors between 0.8-0.9 at full load, dropping significantly at lighter loads.

Q2: How does voltage affect current?
A: Current is inversely proportional to voltage - doubling the voltage halves the current for the same power.

Q3: Why include efficiency in the calculation?
A: Efficiency accounts for power losses in the motor, giving the true current drawn from the supply.

Q4: Is this formula different for three-phase motors?
A: Yes, three-phase formula includes a √3 factor: \( I = \frac{P}{\sqrt{3} \times V \times PF \times \eta} \)

Q5: What's the relationship between HP and watts?
A: 1 HP = 746 watts. Convert HP to watts before using this calculator.