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I have about 2 dozen motors (3 Phase) with built-in thermistors(PTC). A telemechanique motor protection relay is used to interface
thermistor with Motor starter.
One of the motors tripped with indication for shorted thermistor. When i measured thermistor resistance (when motor is cool) it was about
175 Ohms. I checked a healthy motor it was 245 ohms. The catalogue for protection relay recomends to use 1000 ohms resistor to replace the thermistor if thermal trip function is not used.
Can somebody tell me the upper and lower limits of resistance for a healthy thermistor .
thermistor with Motor starter.
One of the motors tripped with indication for shorted thermistor. When i measured thermistor resistance (when motor is cool) it was about
175 Ohms. I checked a healthy motor it was 245 ohms. The catalogue for protection relay recomends to use 1000 ohms resistor to replace the thermistor if thermal trip function is not used.
Can somebody tell me the upper and lower limits of resistance for a healthy thermistor .