3-Phase Motor Current Calculator

3-Phase Motor Current Formula:

\[ I = \frac{P}{\sqrt{3} \times V \times PF \times \eta} \]

Power (P):

watts

Voltage (V):

volts

Power Factor (PF):

(0-1)

Efficiency (η):

(0-1)

Current (I):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is 3-Phase Motor Current?

The 3-phase motor current is the amount of electrical current drawn by a three-phase electric motor when operating under load. It's crucial for proper circuit sizing and protection.

2. How Does the Calculator Work?

The calculator uses the 3-phase current formula:

\[ I = \frac{P}{\sqrt{3} \times V \times PF \times \eta} \]

Where:

\( I \) — Current in amps
\( P \) — Power in watts
\( V \) — Line voltage in volts
\( PF \) — Power factor (0-1)
\( \eta \) — Motor efficiency (0-1)
\( \sqrt{3} \) — Constant for 3-phase systems (≈1.732)

Explanation: The formula accounts for the three-phase power delivery and the motor's power factor and efficiency.

3. Importance of Current Calculation

Details: Accurate current calculation is essential for selecting proper wire sizes, circuit breakers, overload protection, and ensuring safe motor operation.

4. Using the Calculator

Tips: Enter power in watts, voltage in volts, power factor (typically 0.8-0.95), and efficiency (typically 0.85-0.95). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What's typical power factor for motors?
A: Induction motors typically have 0.85-0.95 PF at full load, lower at partial loads.

Q2: How do I find motor efficiency?
A: Check motor nameplate or manufacturer specs. Standard efficiency motors are typically 85-95% efficient.

Q3: Should I use line or phase voltage?
A: Use line-to-line voltage (what you'd measure between any two phases).

Q4: What if my motor is in horsepower?
A: Convert HP to watts first (1 HP = 746 watts) before using the calculator.

Q5: Why is the current higher at startup?
A: Motors draw 5-7x rated current during startup (inrush current) which lasts a few seconds.