Siemens SIMOCODE pro

Motor protection
SIMOCODE pro
GWA 4NEB 631 6050-22 DS 03
3-15
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.
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"!
Response at trip level
Response to sensor fault
QE1
QE2
QE3
QE4
QE5
Event
- Thermistor short circuit
Thermistor
input
BU
Tripping
υ
R
See
Table 3-2
See
Table 3-2
- Thermistor trip level
- Thermistor open circuit
Thermistor
T1
T2