GB198950A - Improvements in or relating to electric rectifiers and methods of operating the same - Google Patents

Abstract

.198,950. Naamlooze Vennootschap Philips' Gloeilampenfabrieken, and Holst, G. Sept. 11, 1922. Arc and spark-gap apparatus, arrangements of. -In a rectifier in which an arc discharge takes place in a closed vessel containing inert gas, the cathode being maintained at incandescence by the arc and the anode being relatively cool, the electrodes are so shaped and arranged and the composition and pressure of the gas filling are so chosen that a glow discharge occurs at ordinary supply voltages and automatically initiates the arc discharge. As shown in Fig. 1, the cathode 3 is of tungsten, molybdenum, or other refractory material, and of such a size that it is heated to incandescence (preferably beyond 2000‹ C.) by the arc discharge. The glass envelope 1 is filled with a rare gas to which is added a small volume of another rare gas having an ionization potential lower than the tension whereby the first inelastic collision in the first gas occurs, for example neon may be admixed with 0.5 to 5 per cent of argon by volume, preferably 1 per cent. With this mixture and a supply voltage of 220 volts the gas pressure may be 25 to 40 cm. of mercury, the distance between the electrodes being 0.5 m.m. The gas pressure may be higher than this if auxiliary devices are provided to initiate the glow discharge; for example, an auxiliary electrode may be provided opposite the cathode lead, or a heating-coil may be arranged close to the cathode. A potentiometer GH is connected across the mains and a resistance KM of equal value is arranged parallel thereto. A slider OP enables the full line pressure to be applied for starting the glow discharge; this pressure is then reduced whilst maintaining a constant resistance HP + OK in the circuit of the rectifier and the battery 33 being charged. Alternatively, a transformer may be employed, a two-way switch enabling the rectifier to be connected across the mains in series with a resistance for starting, and then in series with the transformer secondary, which may be adjustable, an adjustable resistance, and the battery to be charged. The switch may be operated electromagnetically. In the arrangement shown in Fig. 3 an auxiliary electrode 18, for example of magnesium, is employed for starting the glow discharge between the electrodes 16, 18, the arc being then established between identical electrodes 16, 17. This arc is finally transferred to the electrodes 17, 15 for rectifying and the battery put in circuit. A three-way switch 20 is moved in succession to contacts c, d, e for these operations. In a further arrangement, Fig. 4, two rectifiers 25, 26 are connected to the halves 29, 30 of the secondary winding of a transformer so constructed that the secondary tension falls rapidly with increase of current. the current passing through the rectifiers 25, 26 during alternate half-periods. Specification 181,675, [Class 39 (i), Electric lamps, Arc &c.], is referred to.