In three-phase systems, what is the formula to calculate current from kVA and voltage?

In three-phase systems, what is the formula to calculate current from kVA and voltage?

• A. kVA = V x I
• B. kVA = V x I x 1.73
• C. kVA = I x R
• D. kVA = I x T

Answer: (B)

In three-phase systems, power is distributed across three wires, which is why the calculation for current involves a factor known as the square root of three, approximately equal to 1.73. The formula you would use to calculate the current from kilovolt-amperes (kVA) and voltage in a three-phase system is given as kVA = V x I x 1.73.

To break it down further, in a three-phase system, power is not just the product of voltage and current; you must account for the phase difference and the fact that there are three phases working together to deliver the power. Thus, the correct formula integrates the factor of √3 (or 1.73) because it adjusts for the geometry of the three-phase system, allowing you to accurately calculate the total current flowing through the system given a specific amount of power (in kVA) and voltage.

This understanding is pivotal for electrical professionals, as it ensures proper calculations are made when designing or troubleshooting three-phase electrical systems.