Controls
Standard Protections
levels at which this may occur. It is diffi cult to defi ne an exact voltage sag or voltage level at which a particular motor will no longer consume power, but we are able to make some general statements concerning MPL protection:
The chiller will remain running under the following conditions:
•Line-voltage sag of 1.5 line cycles or less for any voltage magnitude sag
•Control-voltage sags of less than 3 line cycles for any magnitude sag
•Control-voltage sags of 40 percent or less for any amount of time
•Second-order or lower harmonic content on the line
The chiller may shut down under the following conditions:
•Line-voltage sags of 1.5 or more line cycles for voltage dips of 30 percentor more
•Control-voltage sags of 3 or more line cycles for voltage dips of 40 percentor more
•Third-order or higher harmonic content on the line
Current Overload Protection
The control panel will monitor the current drawn by each line of the motor and shut the chiller off when the highest of the three line currents exceeds the trip curve. A manual reset diagnostic describing the failure will be displayed. The current overload protection does not prohibit the chiller from reaching its full-load amperage.
The chiller protects itself from damage due to current overload during starting and running modes, but is allowed to reach full-load amps.
High Motor-Winding Temperature Protection
This function monitors the motor temperature and terminates chiller operation when the temperature is excessive. The controller monitors each of the three winding-temperature sensors any time the controller is powered up, and displays each of the temperatures at the service menu. Immediately prior to start, and while running, the controller will generate a latching diagnostic if the winding temperature exceeds 265°F(129.4℃) for 0.5 to 2 seconds.
Surge Detection Protection
Surge detection is based on current fl uctuations in one of three phases. The default detection criterion is two occurrences of root-man square (RMS) current change of 30 percent within 0.8 seconds in 60 + 10 percent seconds. With the Tracer chiller controller, the detection criterion is adjustable with the Tracer chiller controller.
Overvoltage and Undervoltage Protection
While some components of the chiller are impervious to dramatically different voltages, the compressor-motor is not. The control panel monitors all three line-to-line voltages for the chiller, and bases the over and undervoltage diagnostics on the average for the three voltages. The default protection resets the unit if the line voltage is below or above ±10 percent of the nominal for 60 seconds.
Power Factor and kW Measurement
Three-phase measurement of kW and unadjusted power factor yields higher accuracy during power imbalance conditions.
