Motor thermal protection device and operation method thereof

An operation method of a motor thermal protection device which utilizes a power supply of a motor for power supplying and comprises a capacitor timing unit, a power-off time determining unit and a heat accumulation calculating unit, and the method comprises:

• timing, by the capacitor timing unit, after the motor is powered off;
• performing, by the power-off time determining unit, a reading operation of reading an output voltage of the capacitor timing circuit after the motor is powered on, and determining, by the power-off time determining unit, a power-off time from when the motor is powered off to when the motor is powered on according to the output voltage;
• and
• calculating, by the heat accumulation calculating unit, a remaining heat accumulation when the motor is powered on according to the power-off time and a heat accumulation when the motor is powered off.