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Three phase is used to provide 480 volts of electric to motors and other devices. Three wires are required and are typically labeled L1. L2. L3.

The voltage between phases should be balanced. To check the voltage balance, measure and record the voltage across each phase. Calculate the average of these readings. Determine the mazimum deviation from the average. This is the defference between the average volts reading and the reading that is the furtherest from the average.

The votage unbalance is then the maximum deviation divided by the average voltage multiplied by 100%.

The average voltage unbalance should be less that 1%.

Example:

L1-L2 = 471 V

L1-L3 = 476 V

L2-L3 = 473 V

Average = 473 V

Max. Deviation = 473 V

Voltage unbalance = (3/473) X 100% = 0.6%

The amperage should be checked for unbalance also. The calculation is the same just replace voltage with amperage. The amperage unbalance should be less than 5%.



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