| 摘要 |
<p>770,997. Automatic control systems for arc furnaces. BRITISH THOMSON-HOUSTON CO., Ltd. Feb. 9, 1955 [Feb. 12, 1954], No. 4221/54. Class 38 (4). In order to prevent excessive operation of a surge-actuated circuit-breaker in the supply to an arc furnace electrode, an amplidyne generator supplying an electrode-positioning motor has a field energized when a surge exceeds a value somewhat below that at which the circuit-breaker is operated, whereby the electrode is withdrawn to tend to reduce the surge. As applied to a three-phase arc furnace, an electrode-positioning motor 7 is connected with an amplidyne generator 8 in a Ward-Leonard loop, the generator field winding 18 being energized to maintain a constant ratio of arc voltage to arc current. The circuit-breaker trip device 4 and a relay 5 are responsive to excessive electrode current signals in current transformer windings 1,' 2, 3, the relay being actuated at a lower surge value than the trip to energize a relay winding 16, and thus close a contact 26 to energize a second generator field winding 28 from a D.C. source. The motor 7 is thereby actuated to withdraw the electrodes before the trip operates to break the supply circuit. The electrodes may be separately positioned by individual motors controlled by relays responsive to the current in each phase. The operating, coils in relay 5 and trip device 4 may be connected in series.</p> |
