Unit Start Up
RT-SVX36K-EN 95
Voltage Supply and Voltage Imbalance
Voltage Supply
Electrical power to the unit must meet stringent
requirements for the unit to operate properly. Measure
each leg (phase-to-phase) of the power supply. Each
reading must fall within the utilization range stamped on
the unit nameplate. If any of the readings do not fall within
the proper tolerances, notify the power company to
correct this situation before operating the unit.
Voltage Imbalance
Excessive three phase voltage imbalance between phases
will cause motors to overheat and eventually fail.The
maximum allowable voltage imbalance is 2%. Measure
and record the voltage between phases 1, 2, and 3 and
calculate the amount of imbalance as follows:
V1, V2, V3 = Line Voltage Readings
VD = Line Voltage reading that deviates the farthest from
the average voltage.
Example: If the voltage readings of the supply power
measured 221, 230, and 227, the average volts would be:
VD (reading farthest from average) = 221
The percentage of Imbalance equals:
The 2.2% imbalance in this example exceeds the
maximum allowable imbalance of 2.0%.This much
imbalance between phases can equal as much as a 20%
current imbalance with a resulting increase in motor
winding temperatures that will decrease motor life. If the
voltage imbalance is over 2%, notify the proper agencies
to correct the voltage problem before operating this
equipment.
% Voltage Imbalance =
100 X AV - VD where;
AV
AV (Average Voltage) =
Volt 1 + Volt 2 + Volt 3
3
221 + 230 + 227
= 226 Avg.
3
100 X 226 - 221
= 2.2%
226
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