Trane CVGF-SVU02B-E4 Operation And Maintenance Manual page 65

Current Limit Protection
Current Limit Protections exist to
avoid motor current overload
and damage to the compressor
motor during starting and
running.
The Current Limit Setpoint (CLS)
can be changed from: Front
Panel, External Analog input
(with GBAS option), or Tracer
(Tracer option). Tracer current
setpoint has the highest priority,
unless disabled in the
DynaView ™ Setpoint source
override menu. The External CLS
has second priority, and will be
used if Tracer is disabled or not
installed. The Front Panel
Setpoint has the lowest priority,
and will be used if Tracer and the
External CLS are both disabled.
CVGF-SVU02B-E4
Machine Protection and
Adaptive
Compressor motor current is
continuously monitored and
current is controlled using a
limit function to prevent running
into overload diagnostic trips.
The current limit control logic
attempts to prevent the motor
from shutting down on a
diagnostic trip by limiting
compressor current draw
relative to an adjustable current
limit DynaView ™ CLS.
This setpoint can also be
lowered to provide electrical
demand limiting on the unit as
required. This could also be set
to allow the chiller to continue to
run at a lower load to avoid
tripping off using a diagnostic.
The Current Limit function uses
a PID algorithm (similar to the
Leaving Water Temperature
control) that allows the chiller to
run at the CLS. At machine
startup, or with any setpoint
change the new current limit
setpoint reached after the
filtered setpoint time elapses.
The minimum current limit
setpoint is default set to 40
percent RLA (20-100 percent).
The filtering time default is set
to 10 minutes (0-120 minutes);
however these can be altered
using the TechView ™ . This
filtered setpoint allows for stable
control if the Current Limit
setpoint is adjusted during a run.
Phase Loss Protection
Loss of phase detection protects
the chiller motor from damage
due to a single-phasing
condition. The controls will shut
down the chiller if any of the
three phase currents feeding the
motor are lost. The shutdown
will result in a latching
diagnostic indicating the failure.
Reverse Rotation
Protection
This function protects the
compressor from damage
caused by being driven in the
reverse direction. Incorrect
phase rotation detection results
in a manually resettable
diagnostic. Phase Reversal
protection default is set to
enable, however can be disabled
using TechView .
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