| 摘要 |
PROBLEM TO BE SOLVED: To remove the residual magnetism generated in the substance for carriage consisting of the ferromagnetic substance such as steel material, etc., in the case of having performed handling using a magnet type crane. SOLUTION: A magnet 2 for demagnetization supplied with AC currents I2 in the shape of attenuating oscillation from an AC power source 4 for demagnetization is arranged around a magnet 1 for crane which attracts a substance for carriage such as steel frame W or the like, being excited by being supplied with DC currents I1 from a DC power source 3. Moreover, AC currents I2 are also supplied to the magnet 1 for lifting. Hereby, the magnet 2 for demagnetization and the magnet 1 for lifting generate AC magnetic fields which become smaller gradually with alteration of positive and negative, and by this AC magnetic field, the residual magnetism of the steel frame W is demagnetized by the magnetic hysteresis characteristic. The AC currents I2 are controlled by a microcomputer, based on the residual magnetism detection signal S1 from a magnetic sensor. |
