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CHAPTER 4: PROGRAMMING
239 MOTOR PROTECTION RELAY – INSTRUCTION MANUAL
Courtesy of NationalSwitchgear.com
•
THERMISTOR HOT RESISTANCE: Consult manufacturer's data for the thermistor(s)
installed in the motor and enter the hot resistance value here. If three PTC thermistors
are connected in series, enter the hot resistance of 1 thermistor.
•
THERMISTOR COLD RESISTANCE: Consult manufacturer's data for the thermistor(s)
installed in the motor and enter the cold resistance value here. If three PTC thermistors
are connected in series, enter 3 times the cold resistance value of a single thermistor.
EXAMPLE 1: PTC THERMISTOR
S4:PROTECTION\TEMPERATURE\THERMISTOR\THERMISTOR HOT
RESISTANCE: 10.0 K
S4:PROTECTION\TEMPERATURE\THERMISTOR\THERMISTOR COLD
RESISTANCE: 0.5 K
S4:PROTECTION\TEMPERATURE\THERMISTOR\THERMISTOR
FUNCTION: TRIP
The thermistor trip will occur when the thermistor input resistance is greater than
or equal to the
S4:
\PROTECTION\TEMPERATURE\THERMISTOR\THERMISTOR HOT
setting of
RESISTANCE
The thermistor trip can be reset when the thermistor input resistance becomes
less than the
S4:PROTECTION\TEMPERATURE\THERMISTOR\THERMISTOR COLD
setting of
RESISTANCE
EXAMPLE 2: NTC THERMISTOR
S4:PROTECTION\TEMPERATURE\THERMISTOR\THERMISTOR HOT
RESISTANCE: 0.7 K
S4:PROTECTION\TEMPERATURE\THERMISTOR\THERMISTOR COLD
RESISTANCE: 12.0 K
S4:PROTECTION\TEMPERATURE\THERMISTOR\THERMISTOR
FUNCTION: TRIP
The thermistor trip will occur when the thermistor input resistance is less than or
equal to the
S4:\PROTECTION\TEMPERATURE\THERMISTOR\THERMISTOR HOT
setting of
RESISTANCE
The thermistor trip can be reset when the thermistor input resistance becomes
greater than the
S4:PROTECTION\TEMPERATURE\THERMISTOR\THERMISTOR COLD
setting of
RESISTANCE
•
THERMISTOR NOT CONNECTED ALARM: If the thermistor becomes open circuited
during use, the ACTUAL VALUES display for the thermistor will be "NOT CONNECTED".
The 239 relay will generate an alarm to warn of the fault if this setpoint is enabled.
RTD 1-3 (option)
Protection against excessive motor temperature due to loss of ventilation or high ambient
temperatures is provided by the RTD option which must be ordered with the relay if
required. Up to 3 resistance temperature detectors (RTDs) must be supplied with the motor
Ω
Ω
Ω
.
10.0 K
Ω
.
0.5 K
Ω
Ω
Ω
.
0.7 K
Ω
.
12.0 K
4–43
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