In a three-phase system, the voltage imbalance between any two legs may not vary by more than ______.

In a three-phase system, the voltage imbalance between any two legs may not vary by more than ______.

• A. 2%
• B. 5%
• C. 10%
• D. 0.5%

Answer: (A)

In a three-phase system, the three phase voltages should be as equal as possible. The imbalance is how far any leg’s voltage deviates from the average of the three, expressed as a percent. This matters because even small imbalances create circulating currents and heating in motors and transformers, reducing efficiency and life. The widely used practical limit is about 2 percent. That means the difference between any two legs (or any phase voltage) and the overall average should not exceed 2% of that average. This keeps motors running cooler and more reliably. The other options are less appropriate: 0.5% is unrealistically strict for most real-world systems, while 5% or 10% would allow enough imbalance to cause overheating and performance issues in electrical equipment.

In a three-phase system, the three phase voltages should be as equal as possible. The imbalance is how far any leg’s voltage deviates from the average of the three, expressed as a percent. This matters because even small imbalances create circulating currents and heating in motors and transformers, reducing efficiency and life.

The widely used practical limit is about 2 percent. That means the difference between any two legs (or any phase voltage) and the overall average should not exceed 2% of that average. This keeps motors running cooler and more reliably.

The other options are less appropriate: 0.5% is unrealistically strict for most real-world systems, while 5% or 10% would allow enough imbalance to cause overheating and performance issues in electrical equipment.