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Motor Components; Thermal Motor Protection - Siemens SINAMICS S120 Configuration Manual

Synchronous motors.
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Motor components


Thermal motor protection

A temperature-dependent resistor is integrated as temperature sensor to monitor the motor
Table 6-1
Resistance when cold (20°C)
Resistance when hot (100°C)
The resistance of the KTY 84 thermistor changes proportionally to the winding temperature
The temperature signal is sensed and evaluated in the drive converter whose closed-loop
control takes into account the temperature characteristic of the motor resistances.
When a fault occurs, an appropriate message is output at the drive converter. When the
motor temperature increases, a message "Alarm motor overtemperature" is output; this must
be externally evaluated. If this signal is not observed, the drive converter shuts down with
the appropriate fault message when the motor limiting temperature or the shutdown
temperature is exceeded.
If the user carries-out an additional high-voltage test, then the ends of the temperature
sensor cables must be short-circuited before the test is carried-out!
If the test voltage is connected to a temperature sensor terminal, then it will be destroyed.
The polarity must be carefully observed.
The temperature sensor is designed so that the DIN/EN requirement for
"protective separation" is fulfilled.
Synchronous Motors 1FK7
Configuration Manual, (PFK7S), Edition 12.2006, 6SN1197-0AD16-0BP1
Features and technical data
KTY 84 (PTC thermistor)
approx. 580 Ohm
approx. 1000 Ohm
via signal cable


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