| 摘要 |
597,108. Signalling over power circuits. CLULEY, G., SMITH, R. M. A., and METROPOLITAN-VICKERS ELECTRICAL CO., Ltd. Aug. 9, 1945, No. 20496. [Class 40 (iv)] i j In electric control or signal systems in which the signals consist of medium frequency current superimposed on the commercial supply frequency current in power mains and the signal generator circuit includes a blocking capacitance and a tuning reactance and a switch, at least part of the tuning reactance is included in the circuit between the power circuit and the said switch to limit any fault current. The switch need not therefore be of high rupturing capacity and is thus less costly. In the example shown, a bus-bar B is connected to a feeder F by a high capacity switch FS. The signal circuit comprises a generator G, a condenser C, an isolating switch IS of low capacity and a tuning reactor R. The latter then prevents full fault current reaching switch IS. |
