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CVHE-SVU01E-EN
Current Overload Protection
Motor currents are continuously
monitored for over current protection
and locked rotor protection. This
protects the Chiller itself 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 .
Running Over Current Protection
In the run mode, a “time-to-trip”
curve is looked at to determine if a
diagnostic should be called. The
UCP continuously monitors
compressor line currents to provide
running over current and locked rotor
protection. Over current 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
Rated Load Amps of the compressor
and is not adjustable:
Overload Must Hold = 102 Percent
RLA.
Overload Must Trip in 20 (+0 -3)
seconds = 112 Percent RLA
(Note the above gives a nominal 20
second must trip point of 107 Percent
RLA.)
Overload Must Trip in 1.5 seconds =
140 Percent RLA (Nominal)
The linear time-trip curve is as
follows:
Figure 26. Overload trip time versus percent RLA
The Maximum Acceleration Time
Setting and Current Transformer
Setting are factory set however can
be set with the service tool;
Machine Protection
and Adaptive
Control