Rockwell Automation 825-P Modular Protection System for Motors User Manual - Manual (Page 83)

Rockwell Automation Publication 825-UM004D-EN-P - November 2012 83
Configuring Protection & Logic Functions Chapter 6
You can connect up to six PTC thermistor sensors to the 825-P. The detectors are
typically embedded in the stator winding of the motor and they monitor the
actual temperature of the winding. This function is independent of the thermal
model and accounts for conditions such as ambient temperature, obstructed
cooling, etc. The sensors and their leads are also monitored for short-circuit
faults.
Figure 32 shows characteristics of the PTC. Setting PTC RESET MODE
determines reset mode for the PTC element. If set to Auto mode, the PTC trip
resets automatically when the element resets, if other trip conditions are not
present. If set to Man, operator intervention (e.g., front-panel push button) is
required to reset the PTC trip.
Figure 32 - Characteristic of PTC Sensors as per IEC 34-11-2
RTD-Based Protection RTD Monitoring
When you connect the 825-PR12D RTD Module, the 825-P offers several
protection and monitoring functions whose settings are described in Table 27.
See Figure 4 for the location of the RTD module fiber-optic cable connector.
NOTE: In addition to enabling the PTC function, you must also connect at least one (but no more
than six) thermistor(s) to the relay (see Figure XX for a connection diagram).
4000
1330
550
250
100
20
10
—20 °C
0 °C
TNF
TNF
R (W)
Nominal pickup temperature
Resistance to sensors
TNF — 20 K
TNF — 5 K TNF + 15 K
TNF + 5 K
R (W)
NOTE: The 825-P can monitor up to 12 RTDs connected to the 825-PR12D Module. Table 27 shows
Location, Type, and Trip/Warn Level settings only for RTD1; settings for RTD2 through RTD12
are similar.