1. What is 3 Phase Current Unbalance?

Definition: Current unbalance measures the inequality of current magnitudes in a three-phase system, expressed as a percentage.

Purpose: It helps identify potential issues in electrical systems that can lead to equipment overheating and reduced efficiency.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( I_{unbalance} \) — Current unbalance percentage
• \( I_a, I_b, I_c \) — Phase currents (A)
• \( I_{avg} \) — Average of the three phase currents (A)

Explanation: The formula calculates the average current, then sums the absolute deviations of each phase from the average, and expresses this as a percentage of the average.

3. Importance of Current Unbalance Calculation

Details: Current unbalance can cause motor overheating, vibration, and reduced lifespan. NEMA recommends keeping unbalance below 5%.

4. Using the Calculator

Tips: Enter the measured current for all three phases in amperes. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What causes current unbalance?
A: Voltage unbalance, unequal loads, faulty connections, or motor winding issues can cause current unbalance.

Q2: What's an acceptable unbalance level?
A: Generally, unbalance should be less than 5%. Above 10% is considered severe.

Q3: How does unbalance affect motors?
A: It causes negative sequence currents leading to overheating, torque pulsation, and reduced efficiency.

Q4: Can voltage unbalance be calculated similarly?
A: Yes, the same formula applies using phase voltages instead of currents.

Q5: How often should I check current unbalance?
A: Regular monitoring (monthly or quarterly) is recommended, especially for critical motors.