Description
4.2 Device description
SIRIUS 3RN2 thermistor motor protection relay
Manual, 10/2016, A5E34244868002A/RS-AA/001
23
Color codes
A PTC temperature sensor has a nonlinear change in temperature. However, at a certain
temperature, its resistance increases suddenly. This temperature is known as the rated
response temperature (TNF).
PTC sensors are available on the market with different rated response temperatures, which
are normally chosen by the motor manufacturer based on the maximum permissible motor
temperature and installed in the windings.
Because the resistance characteristic values are identical for all types, you do not need to
concern yourself with the actual temperature limit of the motor. The 3RN2 thermistor motor
protection relay trips reliably when the rated response temperature is exceeded.
You can see the rated response temperatures by the colors of the thermistor sensor cables
because the colors are standardized:
TNF (°C)
Color code
60
white/gray
70
white/brown
80
white/white
90
green/green
100
red/red
110
brown/brown
120
gray/gray
130
blue/blue
140
white/blue
145
white/black
150
black/black
155
blue/black
160
blue/red
170
white/green
180
white/red
Summary of Contents for 3RN2011
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