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CVHE-SVU01E-EN
70
Current Limit Protection
Current Limit Protections exist to
avoid motor current overload and
damage to the compressor motor
during starting and running.
Compressor motor current is
continuously monitored and current
is controlled via a limit function that
to prevent running into over current
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
™
Current Limit Setpoint.
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 via 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
Current Limit Setpoint. At machine
startup, or with any setpoint change
the new current limit setpoint
reached after the is filtered setpoint
time elapses. The minimum current
limit setpoint is default set to 40
percent RLA (20-100 percent). The
filtering time is default set to 10
minutes (0-120 minutes), however
these can be altered via the service
tool. This filtered setpoint allows for
stable control if the Current Limit
setpoint is adjusted during a run.
The Current Limit Setpoint (CLS) can
be changed from: Front Panel,
External Analog input (with GBAS
option), or Tracer (Tracer option).
However, If present 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.
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. The
motor is protected from over-current
during a single-phase condition by
the Current Overload Protection
feature. Phase Loss Protection
provides redundant protection and a
diagnostic that more accurately
describes the fault.
Reverse Rotation Protection
This function protects the
compressor from being driven in the
reverse direction. Incorrect phase
rotation detection results in a
manually resettable diagnostic.
Phase Reversal protection is default
to Enable, however can be disabled
via the service tool.
Phase Imbalance Protection
CH530 provides phase imbalance
protection based on the average
three-phase current. The three phase
currents supplied to the motor are
monitored for unequal amperage
draw. Motor overload is not
considered to be a problem since
each phase of the motor is monitored
for overcurrent. In addition, since
each phase is monitored for loss of
current, the motor will be protected
against single phasing.
Under and Over Voltage Protection
Under/over voltage protection can be
enabled (default) or disabled via
TechView.
If Disabled : No effect.
If Enabled :
and an Overvoltage condition occurs:
-Diagnostic called when the average
of the three line voltages is greater
than 112.5% of the unit line voltage
set point for 60 seconds.
-Diagnostic cleared when the average
of the three line voltages is 110% or
less of the unit line voltage set point.
and an Undervoltage condition
occurs:
-Diagnostic called when the average
of the three line voltages is less than
87.5% of the unit line voltage set
point for 60 seconds.
-Diagnostic cleared when the average
of the three line voltages is 90% or
greater of the unit line voltage set
point.
Machine Protection
and Adaptive
Control