Thermistor Protection - Siemens SIMOCODE pro System Manual

3.5

Thermistor protection

Description
Thermistor protection is based on a direct temperature measurement in the
motor via binary PTC thermistors which can be connected to either basic
unit 1 (BU1) or basic unit 2 (BU2).
Thermistor protection is used for:
• Motors with high switching frequencies
• Converter operation
• Motors with heavy starting
• Intermittent and/or braking operation
• Restricted air supply
• Speeds below the rated speed.
In this case, the sensors are mounted in the winding slot or bearings of the
motor.
Schematic and characteristic curve
The resistance of the thermistors increases rapidly (erratically) when the
temperature limit is reached.
R
Thermistor
input
BU
Fig. 3-5: Thermistor (Thermistor Protection) function block
Response
• Overtemperature:
Here you can select the SIMOCODE pro response if the temperature exceeds
the trip level.
Notice
For motors for EEx e applications, the response must be set to "Tripping"!
SIMOCODE pro
GWA 4NEB 631 6050-22 DS 03
Thermistor
υ
Response at trip level
T1
T2
Response to sensor fault
Motor protection
QE1
QE2
Tripping
QE3
QE4
QE5
See
Table 3-2
Event
- Thermistor trip level
See
- Thermistor short circuit
Table 3-2
- Thermistor open circuit
3-15