Electrical Phasing (Three-Phase Motors) - Trane Horizon OADG Series Installation, Operation And Maintenance Manual

Voltage Imbalance
WARNING
Live Electrical Components!
Failure to follow all electrical safety precautions when
exposed to live electrical components could result in
death or serious injury. When necessary to work with
live electrical components, have a qualified licensed
electrician or other individual who has been properly
trained in handling live electrical components perform
these tasks.
AVERTISSEMENT
Composants électriques sous tension!
Le non-respect de toutes les consignes de sécurité lors
de la manipulation de composants électriques sous
tension peut entraîner des blessures graves, voire
mortelles. S'il est nécessaire de travailler avec des
composants électriques sous tension, demandez à un
électricien qualifié et agréé ou à une autre personne
ayant la formation nécessaire pour manipuler des
composants électriques sous tension d'exécuter ces
tâches.
Three phase 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.
Excessive three phase voltage imbalance between phases
will cause motors to overheat and eventually fail. The
maximum allowable voltage imbalance is 2.0 percent.
Measure and record the voltage between phases 1, 2, and
3 and calculate the amount of imbalance as follows:
% Voltage Imbalance = 100 X
Volt 1 + Volt 2 + Volt 3
AV (Average Voltage) =
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:
221 + 230 + 227
= 226 Avg.
3
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AV - VD
where;
AV
3
VD (reading farthest from average) = 221
The percentage of Imbalance equals:
226 - 221
100 X = 2.2%
226
The 2.2 percent imbalance in this example exceeds the
maximum allowable imbalance of 2.0 percent. This much
imbalance between phases can equal as much as a
20 percent current imbalance with a resulting increase in
motor winding temperatures that will decrease motor life.
If the voltage imbalance is over 2.0 percent, notify the
proper agencies to correct the voltage problem before
operating this equipment.

Electrical Phasing (Three-Phase Motors)

WARNING
Live Electrical Components!
Failure to follow all electrical safety precautions when
exposed to live electrical components could result in
death or serious injury. When necessary to work with
live electrical components, have a qualified licensed
electrician or other individual who has been properly
trained in handling live electrical components perform
these tasks.
AVERTISSEMENT
Composants électriques sous tension!
Le non-respect de toutes les consignes de sécurité lors
de la manipulation de composants électriques sous
tension peut entraîner des blessures graves, voire
mortelles. S'il est nécessaire de travailler avec des
composants électriques sous tension, demandez à un
électricien qualifié et agréé ou à une autre personne
ayant la formation nécessaire pour manipuler des
composants électriques sous tension d'exécuter ces
tâches.
The compressor motor(s) and the supply fan motor are
internally connected for the proper rotation when the
incoming power supply is phased as A to L1, B to L2, and
C to L3.
Proper electrical supply phasing can be quickly
determined and corrected before starting the unit by using
an instrument such as an Associated Research Model 45
Phase Sequence Indicator and following these steps:

Turn off the main source feeding power to the unit
field-supplied or factory-installed main disconnect
device (switch or circuit breaker).

Close the unit disconnect device cover, leaving
disconnect switch in the off position, and turn main
source power on.
Installation
35