AC Motors Temperature Rise of Induction Motors

Motor Temperature Rise

While the motor is running, all internal losses in the motor (such as copper losses, iron losses, etc.) convert into heat, causing the temperature of the motor to rise.

• Induction motors (continuous rating) experience saturation in temperature rise within 2 to 3 hours after starting operation and stabilize at a constant temperature.
• A reversible motor (30 minutes rating) reaches the specified temperature 30 minutes after starting operation. If the operation continues, the temperature will further increase.

Temperature Rise Measurement Method

Oriental Motor specifies the temperature rise of the motor with the values measured using the following methods.

Thermometer Method

Affixes a thermometer or thermocouple to the center of the motor case, operates the motor, and then measures the temperature that results after the temperature rise is saturated, taking its difference from the ambient temperature as the temperature rise.

Resistance Method

This is a method for measuring the winding temperature by monitoring the change in its resistance value. It uses a resistance meter, thermometer etc. to measure the motor winding resistance and ambient temperature before and after operation to obtain the motor’s winding temperature rise value.