Three-Phase Voltage Unbalance Calculator
Calculate a maximum-deviation voltage-unbalance percentage from three line-to-line RMS readings.
Enter measured or design values
Voltage unbalance
This is the maximum-deviation method, not negative-sequence voltage unbalance.
About this calculator
Calculate a maximum-deviation voltage-unbalance percentage from three line-to-line RMS readings.
This maximum-deviation metric is not the negative-sequence voltage-unbalance method and does not apply a universal equipment limit.
Method and assumptions
Average voltage is the arithmetic mean of the three line-to-line readings. Percent unbalance is the largest absolute deviation from that average divided by the average, multiplied by 100.
Enter values measured or specified for the same load, system, and operating condition. These simplified calculations do not model harmonics, transient behavior, or equipment-specific acceptance limits.
FAQs
Does this result establish compliance or equipment acceptance?
No. It is a calculation or screening metric. Apply the equipment manufacturer criteria, project requirements, and locally applicable standards.
Which voltage readings should I enter?
For the voltage screen, enter all three RMS line-to-line readings measured at the same operating condition and point in the system.
Sources
Power triangle and maximum-deviation definitions as stated in the method above. Confirm manufacturer-specific criteria before applying results.