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3.7.2. Temperature measurement with Linear Positive Temperature Coefficient
sensors :
Motor temperature can also be continuously measured by the drive using an LPTC thermal
sensor (or equivalent) built in to the stator winding. LPTC sensors change their resistance
according to an approximately linear characteristic. The required temperature limits for alarm
and tripping can be set in the drive.
The graph below shows the typical characteristics of the resistance vs temperature,
for a current of 5 mA:
With resistance measurement, we
can find the correspondant
winding temperature with the
following formula :
T°C = -0.00006*R²+0.2919*R-128