| 摘要 |
PURPOSE:To switch over a voltage applied to a magnet from an over voltage to a rated voltage easily by a method wherein a switching element is inserted into a part of an arm of a three-phase full-wave rectifier and the switching element is opened and closed. CONSTITUTION:A switching element 12 is inserted into a part of an arm of a three-phase full-wave rectifier 5. When a source is closed a voltage is applied to source side terminals of forward exciting contactors 6a, 6b and reverse exciting contactor 7a, 7b and at this stage the connection between the switching element 12 and the contactors 6a, 6b, 7a, 7b is open. When a switch of an exciter control circuit is closed toward the contraction side a discharge resistor 10 is opened and the switching element 12 is closed, then the contactors 6a, 6b are closed and a magnet 11 is excited. At this stage the exciting voltage is a DC rectified voltage of about 1.35 times of an AC input voltage. When the switching element 12 is opened, a five-element rectifier is composed and the rectified voltage is reduced to about 1.12 times of the AC input voltage. When the switch of the exciter control circuit is closed toward the releasing side the attracting force of the magnet 11 disappears and one turn of operation is completed. |
