Parker NX Series, Technical Manual

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86 - PVD 3663_GB_NX_March 2017.Docx
3.7. Thermal Protection
Different protections against thermal overloading of the motor are proposed as an
option: Thermoswitch, PTC thermistors or KTY temperature built into the stator
winding. No thermal protection are available for the NX1 motor
The thermal sensors, due to their thermal inertia, are unable to follow very fast winding
temperature variations. They acheive their thermal steady state after a few minutes.
Warning: To protect correctly the motor against very fast overload,
please refer to 3.1.6. Peak current limitations
3.7.1. Alarm tripping with PTC thermistors :
One thermal probe (PTC thermistors) fitted in the NX servomotor winding trip the
electronic system at
150°

5° C for class F version. When the rated tripping
temperature is reached, the PTC thermistor undergoes a step change in resistance.
This means that a limit can be easily and reliably detected by the drive.
The graph and tab below shows PTC sensor resistance as a function of temperature
(T
N
is nominal temperature)
Temperature Resistance value for
NX2, NX6 and NX8 Resistance value for
NX3 and NX4
-20°C up to T
N
-20°C
R1≤500Ω R1≤750Ω
TNF-5°C
R2≤1100Ω R2≤1650Ω
TNF+5°C
R3≥2660Ω R3≥3990Ω
TNF+15°C
R4≥8000Ω R4≥12000Ω
R4
Resistance (Ω)
R3
R2
R1
T
N
-
2
0
°C
T
N
-
5
°C
T
N
+
5
°C
T
N
+
1
5
°C
Temperature (°C)
-2
0
°C