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7
6.2.6
Motor thermistor (PTC) connection
There are three possibilities to connect a PTC resistor to Vacon NXL:
1. With optional board OPT-AI. (Recommended method)
Vacon NXL equipped with OPT-AI fulfills IEC 664 if the motor thermistor
is insulated (= effective double insulation).
2. With optional board OPT-B2.
Vacon NXL equipped with OPT-B2 fulfills IEC 664 if the motor thermistor
is insulated (= effective double insulation).
3. With the digital input (DIN3) of NXL.
The DIN3 is galvanically connected to other I/O's of NXL.
This is why reinforced or double insulation of the thermistor (IEC 664) is absolutely required
outside the frequency converter (in the motor or between the motor and the frequency
converter).
Figure 6-28. Motor thermistor (PTC) connection
Note!
The NXL trips when PTC impedance exceeds 4,7 k
Ω
+24 V (terminal 6)
DIN3 (terminal 10, par.2.1.18 = 14)
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External PTC Resistor
GND (terminal 11)
External resistor
4.7 k
Ω
...5.6 k
Ω
It is strongly recommended to use OPT-AI or OPT-B2 board for motor thermistor connection.
If the motor thermistor is connected to DIN3, the instructions above must be followed, otherwise
a serious safety hazard may result from the connection.