Patent GB-505670-A (GB)
Title: Improvements in electric circuits for operating electric discharge devices from an alternating current supply
IPC: H05B41/22
Filed: 1937-11-25
Abstract: 505,670. Discharge lamps. GENERAL ELECTRIC CO., Ltd., PIRANI, M., and RUDENBERG, R. Nov. 25, 1937, Nos. 32634/37 and 21260/38. [Class 39 (i)] In low-pressure gas-filled discharge lamps and like devices having at least one main thermionic electrode and fed from alternating current supplies with the discharge dissipating the greater part of the power drawn from the supply, the ratio of the R.M.S. voltage across the discharge to the open-circuit voltage of the supply is increased, without substantially increasing the power drawn from the supply, by applying in each cycle of the supply an impulsive voltage between two electrodes, one at least an auxiliary electrode, so arranged in the device that nearly the whole discharge path is exposed to the field generated by the impulsive voltage. When the discharge operates in both half waves of the cycle, the im- _ pulsive voltage is applied in both half waves as soon as the supply voltage is sufficient to maintain the discharge once it is started; the sign of the impulsive voltage may, but need not, be reversed in opposite half cycles. When the discharge operates only in alternate half cycles as where one only of the main electrodes is thermionic, the impulsive voltage may, but need not, be applied in all half cycles. The impulsive voltage may be used to control the discharge to form a flashing sign or aircraft beacon or for signalling. The, peak value of the impulsive voltage is not less than 7 times its R.M.S. value and not greater than 10 times the supply voltage. The impulsion voltage is not generated by a Tesla coil but may be supplied by a transformer 17 the secondary 6 of which is connected between one of the main electrodes 2, 2<1> and a central auxiliary electrode 5. As shown, the transformer has a saturatable core and its primary 7 is fed through a choke 18 and resistance 19 adjusting the phase of the impulsive secondary voltage. Alternatively, the transformer is fed through an interrupter and resistance, with a condenser across the primary and the interrupter, Fig. 1 (not shown), or through a resistance, a condenser and a discharge device of selected starting voltage, Fig. 2 (not shown), or through a resistance and negative glow discharge lamp with a condenser across this lamp and the primary, Fig. 5 (not shown). The internal electrode 5 may be replaced by an external electrode and extending most of the way between the electrodes 2, 21, in the form of a helical wire or painted coating or a strip with side projections. The helical wires of two tubes in series may be connected together. To increase the rate of increase of discharge current when it begins to flow in each cycle, a second auxiliary electrode 51 may be supplied with impulsive voltage by a transformer 21 with saturable core. Neon, sodium and mercury lamps are referred to and details are given for a lamp filled with neon at 4 mm. pressure and argon at À002 mm. pressure, also for a lamp coated with luminescent material and filled with argon at 2 mm. pressure and mercury. Specification 14170/03, [Class 39 (i)], is referred to.