| 摘要 |
<p>1309972 Protective arrangements SOC D APPAREILLAGE ELECTRIQUE SAPAREL 19 April 1971 [16 March 1970] 24116/71 Heading H2K In an earth leakage protective arrangement comprising a core-balance transformer 1 having its secondary winding 2 supplying a relay 3 controlling a circuit-breaker 20, any residual magnetism is removed from the transformer core by the automatic connection of a demagnetizing circuit to the secondary winding when the circuit-breaker opens. The demagnetizing circuit is connected by a changeover switch 6 formed by time delayed contacts of the circuit-breaker 20, or by the contacts of a further relay having its coil connected downstream of the circuit-breaker. The demagnetizing circuit may comprise an A.C. source 4 in series with a positive temperature coefficient resistor 5, or in parallel with a negative temperature coefficient resistor, Fig. 2 (not shown). In a further arrangement, the winding 2 is connected through the switch in series with the A.C. terminals of a bridge rectifier to two conductors of the protected supply, a capacitor being connected across the D.C. terminals of the bridge, Fig. 3 (not shown). In another arrangement a charged capacitor in series with an inductor is connected across the secondary winding on the opening of the circuit-breaker, Fig. 4 (not shown).</p> |
