| 摘要 |
423,377. Control of A.C. motors. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.-(Assignees of Seeley, H. T. ; 512, Orchard Avenue, Yeadon, Lansdowne P.O., Pennsylvania, U.S.A.) Sept. 22, 1933, No. 26192. Convention date, Sept. 22, 1932. [Class 38 (iii)] A load-responsive relay 6, which effects a predetermined increase of the excitation of a synchronous motor 1 at a predetermined load value, is supplied with a compensating current which causes it to pick-up and dropout at substantially the same value of load. The compensating current is supplied from a transformer 15 through an impedance 14 of suitable value. At the predetermined load value the relay 6 closes its upper contacts 8 and energizes a relay 5 which cuts out resistance 3 from the motor field circuit. A selfmaintaining relay 9 is also energized and maintains the relay 5. When the load falls slightly below the predetermined value, the relay 6 drops out and de-energizes the relay 9 which de-energizes the relay 5 to restore the field to its normal value. |
