| 摘要 |
PURPOSE:To obtain a semi-permanent life and realize high insulation by closing a contact switch when at least one of multiple noncontact switches is closed, and opening the contact switch when all multiple noncontact switches are opened. CONSTITUTION:When all semiconductor control elements 13a-13d are to be opened while one semiconductor control element 13d is closed and other semiconductor elements are opened, a control circuit 15 cuts off the gate signal to open the semiconductor control element 18d based on the off-action of the lowest-stage remote control switch 6A. The circuit 15 detects that all elements 13a-13d are opened and drives a mechanical switch 12 to open a main circuit contact 125, and the insulation of the circuit is secured. The circuit frequently opened or closed is on/off-controlled by semiconductor control elements, and the main circuit contact is opened only when all branch circuits are opened.
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