| 摘要 |
<p>342,385. Protective cut-out systems. SIEMENS - SCHUCKERTWERKE AKT.- GES., Siemensstadt, Berlin. Nov. 7, 1929, No. 34042. Convention date, Nov. 9, 1928. [Class 38 (v).] A device for releasing A.C. switches on shortcircuit comprises a rapid-acting circuit-breaker in combination with means which is practically independent of the A.C. working potential and acts more quickly than the working current to release the switch in response to conditions in the circuit. Preferably high-frequency currents are employed and are fed into the line 13 by a generator 16 connected to the mid-point of the primary of a transformer 22. An ohmic, inductive, or capacity resistance 21 is normally adjusted so that no potential is impressed on the secondary of transformer 22, but a short-circuit on line 13 causes an increase of current in the half of the primary connected with that line, and sets up a high-frequency potential in the secondary, which potential is rectified and passed through a thermionic amplifier 23 to the release coil 24 of the rapid-acting switch 25. If a frequency of 50000 cycles is injected in a 50-cycle circuit, the switch will be released in about one-thousandth of the time taken by the working frequency. The Specification also refers to the use of the natural frequencies of lines and to D.C. injections.</p> |
