Question:
Is the motor overload detection (I²xt) sufficient as motor temperature monitoring for a self-ventilated motor?
Answer:
Basically it is possible to use the motor overload detection (I²xt) as motor temperature monitoring for a self-ventilated motor in the entire setting range. However, the 'I²xt' function is always reset when switching the mains of the frequency inverter so that the function assumes that the motor is not thermally preloaded when the frequency inverter is restarted. The ambient temperature of the motor is not considered. This leads to an additional inaccuracy. For these reasons, it is not possible to ensure a full thermal motor protection using the motor overload detection (I²xt).
Note:
For a full thermal motor protection, connect a PTC thermistor or a thermal contact.
