| 摘要 |
PROBLEM TO BE SOLVED: To provide a device for protecting an electric motor from excessive temperature rise which is capable of detecting excessive temperature rise inside a small size electric motor and of protecting the motor by letting a protective function work against the excessive temperature rise immediately to prevent the burning of wire, etc., even if a sharp temperature rise occurs. SOLUTION: In a AC or DC electric motor 4, a magnet having flux density highly dependent on temperature is used as a position detecting magnet 4a provided on a rotor of an AC electric motor and a position detecting magnet 4a provided corresponding to a field magnet 4d provided on a rotor of a DC electric motor, and the number of rotation is controlled by detecting the rotating position of the magnetic pole of the position detecting magnet 4a with a rotating position detecting element 4b. In addition, excessive temperature rise inside the electric motor is detected by a comparison signal obtained by comparing the position detecting signal with a reference signal by a comparison circuit to let a protective function work against the excessive temperature rise. |
