| 摘要 |
<p>PURPOSE:To prevent generation of arc discharge on the side of normally-chased contacts, by composing an exciting circuit of magnetic switches only when each of the normally-open contacts of a forward-backward movement magnet switch is open. CONSTITUTION:When a key switch 17 is closed and a forward movement switch 15 of a forward-backward movement changeover switch 14 is closed, a thyristor 21 becomes conductive, and an exciting coil 61 is loaded, closing normally-open contacts 81 and 91. A motor 2 rotates in the forward direction when these contact 81 and 91 are closed. When the forward movement switch 15 is open and at the same time a backward movement switch 16 is closed in this situation, as a transistor 31 is conducting while the contacts 81, 91 are closed, the thyristor 21 is blocked. When the contacts 81, 91 are opened, the transistor 31 is opened, so that the thyristor 21 becomes conductive and an exciting coil 62 is loaded, closing normally-open contacts 82 and 92. The motor 2 rotates in the backward direction when these contacts 82 and 92 are closed.</p> |
