Trane CSRA025FAF0, Installation Operation & Maintenance

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CSRA-SVX02A-EN 51
System Pre-Start
Procedures
Note: To avoid possible equipment damage, do not use untreated or
improperly treated system water.
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:
% Voltage Imbalance = where;
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:
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.
Scroll Compressor Current Imbalance
Typically, current imbalance is associated with loss in motor efficiency,
higher operating motor temperature, loss of performance and reliability.
With the designs of specialized motors such as those used in the Trane
scroll compressor, operating temperature, efficiency, performance, and
reliability has been taken into account in the total performance of the
compressor.
Current imbalance in a scroll compressor can typically vary from 4 to 15
percent with balanced line voltage. This imbalance occurs because not all of
the winding turns see the same amount of stator iron. The variance of iron
within the motor is to accommodate design requirements for motor cooling
and oil return.
100
AV VD –
AV
----------------------
Volt
1
Volt
2
Volt
3 + +
3
--------------------------------------------------------
221 230 227 + +
3
---------------------------------------
226 Avg
·
=
100226 221
–
226
------------------------
2.2 =