GB277972A - - Google Patents

Abstract

277,972. Hewittic Electric Co., Ltd., (Assignees of Becq, A., Hewittic Soc. Anon., and Demontvignier, M.). Sept. 21, 1926, [Convention date]. Vapour apparatus, arrangernents of. - In a mercury-vapour rectifier means are provided (a) for protecting a bimetallic element for the starting electrode (b) or opening the circuit of the element after starting, and (c) for ensuring closing the output circuit only after starting has been effected. As shown in Fig. 1, a bimetallic element 3 operating a starting electrode 5 is enclosed in a protective screen 7 of glass or other insulating material. The electrode 5 is of tungsten, and slides in a glass sleeve 8 having a flange supporting the screen 7. The element 3 is adjusted so that when the rectifier is in operation the end of the electrode 5 is at the surface of the mercury so as to localize the cathode glow. After starting, the heating current of the element 3 is opened by a relay, and the potential of the electrode 5 remains the same as that of the cathode. As shown in Fig. 3, the secondary winding 22 of a transformer is connected in series with the starting electrode 5 through a resistance 23 and the contacts of relay 26, the winding of which is shunted across the rectifier by a connection through an inductance 18 with the cathode, and through a resistance 25 with the neutral point of the primary 20 of the transformer supplying the anodes 10. The shunt circuit maintains the arc. A circuit breaker 27 in the output circuit has its winding controlled by the contacts 28 of a maximum current relay in the output circuit or by contacts 29 controlled by the winding 26 so that (a) the circuit-breaker cannot be closed when the rectifier is not started across its shunt and (b) in case of failure of the alternating current supply the rectifier cannot be started on load. In the arrangement shown in Fig. 4, the arc is maintained by auxiliary electrodes 33 connected through inductances 34 with the secondary of a transformer 32. The heating circuit of the electrode 5 is opened at. the contacts 37 of a relay 36. The output circuit has a circuit-breaker with a winding 42 controlled by a maximum current relay 41, by contacts 38 of the relay 36, and by push-button switches 45, 46. Auxiliary contacts 43 in the circuit-breaker shunt the switch 45 and control the insertion of a resistance 44. Gratings or casings around the anodes may be connected by relays to the cathode or anodes so as to present starting under load. In order to prevent the passage of continuous current through the starting electrode a condenser may be included in its circuit.