Siemens SIMOTICS M 1PH8 Configuration Manual page 203

The chain of PTC thermistors can also monitor the winding temperature. PTC thermistors are
thermistors that exhibit a sudden increase in resistance at a certain trigger temperature. The
trip units detect this resistance change and signal the trigger temperature. PTC thermistors
are standardized in DIN 44081.
Circuit design
Option A12 consists of two chains of PTC thermistors, each with 3 PTC thermistors for alarm and
trip. The chain of PTC thermistors is installed in the phase elements on the winding overhang.
The temperature difference between alarm and trip is 10 K.
The terminal designations for the two connection ends of the chain of PTC thermistors for
alarm are 1TP1 and 1TP2; the terminal designations for the two connection ends of the PTC
thermistor circuit for tripping are 2TP1 and 2TP2.
The circuit diagram and the terminal assignments are provided in the terminal box of the
1PH8 motor.
Figure 5-14
1PH8 SIMOTICS M main motors
Configuration Manual, 12/2022, A5E51895839A
Chains of PTC thermistors option A12
Motor components and options
5.2 Options
201