GE 239 Instruction Manual page 68

4 PROGRAMMING
assumes a PTC thermistor connection when the +27 5(6,67$1&( is programmed > &2/' 5(6,6
7$1&( . The 239 assumes a NTC thermistor connection when the &2/' 5(6,67$1&( is programmed
≥ +27 5(6,67$1&( . PTC thermistors are preferred because three PTC thermistors can be con-
nected in series to monitor each of the stator phases. This is not possible with NTC thermistors
because all three thermistors must be hot to obtain a fault indication. Select OFF if no thermistor
is installed. If the motor is still overheated after a trip, the thermistor signal will prevent restarting
of the motor by tripping the 239 immediately after reset. Thermistor temperature will be displayed
as either hot or cold because the thermistor is nonlinear. If the thermistor function is to be used
for process control, assign it to the auxiliary relay in which case the auxiliary relay will activate but
no message will be displayed.
• 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.
4
EXAMPLE 1: PTC THERMISTOR
6 3527(&7,21?7(03(5$785(?7+(50,6725?7+(50,6725 +27 5(6,67$1&(  NΩ
6 3527(&7,21?7(03(5$785(?7+(50,6725?7+(50,6725 &2/' 5(6,67$1&(  NΩ
6 3527(&7,21?7(03(5$785(?7+(50,6725?7+(50,6725 )81&7,21 75,3
The thermistor trip will occur when the thermistor input resistance is greater than or equal to
the 6 ?3527(&7,21?7(03(5$785(?7+(50,6725?7+(50,6725 +27 5(6,67$1&( setting of  NΩ .
The thermistor trip can be reset when the thermistor input resistance becomes less than the
6 3527(&7,21?7(03(5$785(?7+(50,6725?7+(50,6725 &2/' 5(6,67$1&( setting of  NΩ .
EXAMPLE 2: NTC THERMISTOR
6 3527(&7,21?7(03(5$785(?7+(50,6725?7+(50,6725 +27 5(6,67$1&(  NΩ
6 3527(&7,21?7(03(5$785(?7+(50,6725?7+(50,6725 &2/' 5(6,67$1&(  NΩ
6 3527(&7,21?7(03(5$785(?7+(50,6725?7+(50,6725 )81&7,21 75,3
The thermistor trip will occur when the thermistor input resistance is less than or equal to the
6 ?3527(&7,21?7(03(5$785(?7+(50,6725?7+(50,6725 +27 5(6,67$1&( setting of  NΩ
The thermistor trip can be reset when the thermistor input resistance becomes greater than
the 6 3527(&7,21?7(03(5$785(?7+(50,6725?7+(50,6725 &2/' 5(6,67$1&( setting of  NΩ .
• 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.
b) RTD 1-3 (OPTION)
Protection against excessive motor temperature due to loss of ventilation or high ambient tempera-
tures is provided by the RTD option which must be ordered with the relay if required. Up to 3 resis-
tance temperature detectors (RTDs) must be supplied with the motor to use this option. When
ordering a motor with RTDs, the 100 Ω platinum DIN 43730 type is the preferred choice for optimum
sensitivity and linearity. Other RTDs that can be selected are 100 Ω nickel, 120 Ω nickel and 10 Ω
copper.
4-30
Courtesy of NationalSwitchgear.com
239 Motor Protection Relay
4 PROGRAMMING
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GE Multilin