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module, mounted in the power panel, utilizes a 7 seg-
ment display which provides operating status and fault
diagnostic information. The 7 segment display will dis-
play either a stationary or a flashing alphanumeric value
which can be decoded by the operator:
TABLE 1 – MOTOR PROTECTOR FAULTS
0
NORMAL - NO FAULT DETECTED
FLASHING "0" MOTOR OFF OR UNLOADED < 5A AC
CURRENT LEVEL
1
HIGH CURRENT FAULT
2
LOADED PHASE TO PHASE CURRENT
IMBALANCE > 17%
3
UNLOADED PHASE TO PHASE
CURRENT IMBALANCE > 25%
4
IMPROPER INCOMING PHASE
ROTATION
5
HIGH MOTOR TEMPERATURE
TRIP POINT = 13 KOHM RESET =
3.25 KOHM
6
COMMUNICATION ERROR
E
OUT OF RANGE OF RLA CALIBRATION
OTHER
DEFECTIVE MODULE OR SUPPLY
SYMBOLS
VOLTAGE
Whenever a motor protector trips, the motor protector
contacts wired in series with the motor contacts, open
and the motor contactor de-energizes allowing the mo-
tor to stop. The microprocessor senses the low motor
current and shuts the system down. The microproces-
sor will try two more starts before locking the system
out. The system locks out because the motor protector
is a manual reset device. After the first start the protec-
tor contacts will be open, thus preventing the motor
contactors from energizing. Power must be removed
and re-applied to reset the module.
Current Overload
The protector module uses integral current transform-
ers per phase to provide protection against rapid cur-
rent overload conditions. The module responds to
changes in current and must be set-up using the DIP
switches located on the module (refer to Section 5 for
details). Integral trip curves allow for in-rush currents
during Star/Delta starting without nuisance tripping.
Thermal Overload
Three PTC (positive temperature coefficient) ther-
mistors in the motor windings of each phase provide
YORK INTERNATIONAL
thermal protection. The sensor resistance stays rela-
tively constant at 1 kW until a temperature of 266°F
(130°C) is sensed. The sensor experiences a rapid rise
in resistance beyond this temperature. Whenever the
resistance of one of the sensors reaches 13 kW, the mod-
ule trips, which ultimately de-energizes the motor's
pilot circuit. Reset is manual after the motor cools and
the sensor resistance drops to 3.25 kW.
Current Unbalance (Loaded & Unloaded)
Loss of Phase
A 2 second delay at start-up allows for any unbalances
resulting during normal starting conditions. After this
initial delay, the protector module compares the "Op-
erating Current" to the measured half line current. The
"Operating Current" is given by 0.65 x factory over-
load current setting.
An unloaded compressor condition occurs when any
measured half line current is less than the "Operating
Current." A current unbalance exceeding an unloaded
level of 25% will result in the motor pilot circuit being
de-energized.
A loaded compressor condition occurs when any mea-
sured half line current is greater than or equal to the
"Operating Current." A current unbalance exceeding a
loaded level of 17% will result in the motor pilot cir-
cuit being de-energized.
Improper Phase Sequence
The protector module calculates the phase sequence at
start-up using the three current transducers to deter-
mine whether the three phase sequence on the load side
of the main contactor is miswired. Upon detection of a
miswired motor load, the module will de-energize the
main contactor pilot circuit within 50 millisecond re-
sponse time.
KEYPAD CONTROLS
For a detailed description of the keypad controls refer
to the Microprocessor Based Control System Operat-
ing Section 7.
Status Key
This key provides a display of the current operational
and/or fault status of the unit or the individual refriger-
FORM 201.25-NM1 (302)
2
13
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