Power Factor Formula for Motor

Power Factor Formula (3-phase):

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

Power Factor (PF):

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1. What is Power Factor for Motors?

Definition: Power factor is the ratio of real power (watts) to apparent power (volt-amps) in an AC electrical system.

Purpose: It measures how effectively electrical power is converted into useful work output by a motor.

2. How Does the Power Factor Calculation Work?

The calculator uses the formula for 3-phase systems:

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

Where:

\( PF \) — Power factor (unitless, between 0 and 1)
\( P_w \) — Real power (watts)
\( V \) — Voltage (volts)
\( I \) — Current (amps)

Explanation: The formula calculates the ratio between the actual power being used (watts) and the apparent power being drawn from the supply (volt-amps).

3. Importance of Power Factor

Details: A higher power factor (closer to 1) indicates more efficient power usage, reduces energy losses, and may lower electricity costs.

4. Using the Calculator

Tips: Enter the motor's real power in watts, line voltage (default 480V for industrial motors), and current in amps. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is a good power factor for motors?
A: Most motors have a power factor between 0.85-0.95 at full load. Below 0.85 may indicate inefficiency.

Q2: Why is √3 used in 3-phase calculations?
A: The √3 factor accounts for the phase difference in three-phase systems (120° between phases).

Q3: How can I improve motor power factor?
A: Use power factor correction capacitors, avoid motor oversizing, and ensure proper maintenance.

Q4: Does power factor change with load?
A: Yes, power factor is typically lowest at no load and improves as the motor approaches full load.

Q5: What's the difference between leading and lagging PF?
A: Lagging PF (common for motors) means current lags voltage. Leading PF (capacitors) means current leads voltage.