PURPOSE: To suppress the surge voltage in a demagnetizing device by providing a rectifier such as a diode or the like at a power control element, and providing a capacitor having a large capacity at the output side of the rectifier, thereby absorbing the storage energy when the polarity is inverted.
CONSTITUTION: Diodes D5WD8 are connected in anti-parallel to control transistors Tr1WTr4, and a capacitor C1 is provided. When transistors Tr1, Tr4 are turned from ON to OFF, the reverse voltage of an electromagnetic chuck 5 is circulated from the diode D6 through the capacitor C1 and the diode D7 to the chuck 5. Accordingly, when the capacity of the capacitor C1 is sufficiently increased, the voltage can be suppressed to not so high value as compared with the power voltage of a rectifier 2. Further, the reverse voltage which becomes position through the diode D6 and negative through the diode D7 becomes the state that the approximate voltage of the rectifier 2 even at the normal switching, and the attenuation of the current due to the storage energy can be accelerated.
IWASAKI HIROSHI
IKEHARA NAOHARU
FUKUSHIMA KAN
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