| 摘要 |
556,467. Protective cut-out arrangements. WILKINS, S. R., and AUTOMATIC COIL WINDER & ELECTRICAL EQUIPMENT CO., Ltd. March 30, 1942, No. 4210. [Class 38 (v)] A transformer has windings 12, 13 supplying high voltages to the anode and screen grid of a thermionic valve over rectifiers (not shown), and a winding 14 supplying unrestricted A.C. to the heater. The anode and screen grid leads 15, 16 include windings 21, 22 of a polarized relay 20, the armature 23 of which normally holds the contacts 15b, 16b closed by the polarizing field assisted by the windings 21, 22. If, due to failure of a smoothing condenser or rectifier, or to a wrong connection to the winding 14 whereby the valve heater is connected to leads 15, 16. an excessive alternating current flows in either winding, the polarizing field is neutralized in the first reverse half-cycle and a spring 25 pulls off the armature and opens the supply. In the event that the same alternating current could flow in opposite directions through windings 21, 22, thereby neutralizing their effects, one of them may have more turns than the other. A manual resetting means for the switch may be provided, and a back-contact 26 on the armature may make an indicator circuit. A construction of switch 20 is illustrated, Figs. 2, 3 (not shown). Each of the windings 21, 22 may act as polarizing field to the other. |
