Trane CVGF-SVU02B-E4 Operation And Maintenance Manual page 64

Current Overload
Protection
Motor currents are continuously
monitored for over current
protection and locked rotor
protection. This protects the
chiller from damage due to
current overload during starting
and running modes but is
allowed to reach full load amps.
This overload protection logic is
independent of the current limit.
The overload protection will
ultimately shut the unit down
anytime the highest of the three
phase currents exceeds the time
trip curve. A manual reset
diagnostic describing the failure
will be displayed.
Overload protection for the
motor starts based on the
maximum time to transition
permitted for a particular motor.
64
Machine Protection and
Adaptive
Running Overload Protection
In the run mode, a time trip
curve is looked at to determine if
a diagnostic should be called.
The starter LLID continuously
monitors compressor line
currents to provide running
overload and locked rotor
protection.
Overload protection is based on
the line with the highest current.
It triggers a manually resettable
diagnostic shutting down the
compressor when the current
exceeds the specified time trip
curve. The compressor overload
time trip curve is expressed as a
percent of the RLA of the
compressor and is not
adjustable:
Figure 22. Overload time trip versus percent RLA
Overload Must Hold = 102
Percent RLA.
Overload Must Trip in 20 (+0 -3)
seconds = 112 Percent RLA
(Note the above gives a nominal
20 seconds must trip point of
107 Percent RLA.)
Overload Must Trip in 1.5
seconds = 140 Percent RLA
(Nominal)
The time trip curve is as follows:
Nominal Triptime
(Sec)
Minimum Triptime
(Sec)
Maximum Triptime
(Sec)
CVGF-SVU02B-E4