| 摘要 |
<p>981,752. Protective arrangements. ENGLISH ELECTRIC CO. Ltd. June 7, 1961 [June 9, 1960], No. 20256/60. Heading H2K. [Also in Division H3] A protective arrangement has timing means comprising a capacitor 12 arranged to be charged by a unidirectional overcurrent or overvoltage operating signal, non-linear resistor means connected in parallel with the capacitor to retard its charging when the signal is relatively high, and non-linear resistor means connected in series with the capacitor to retard its charging when the signal is relatively low. In Fig. 1 the parallel-connected non-linear resistor means comprise rectifiers 4, 5 in series with resistors 18, 29 and the series-connected non-linear resistor means comprise rectifiers 6 and resistors 32, 33, though in Fig. 2 (not shown) the rectifiers may be replaced by voltage-dependent resistors. In each case the capacitor 12 may be shunted by a normally-conducting transistor T1 which is rendered non- conducting when the signal reaches a predetermined magnitude. The timing means may be connected to a transistorized measuring and tripping circuit such as that of Specification 958,774. It is stated that the provision of the non-linear resistor means results in a relay characteristic curve which corresponds with that of British Standard Specification No. 142.</p> |
