GB429297A - Means for operating gas-filled luminescent tubes - Google Patents

Abstract

429,297. Supply systems for vacuum &c. lamps; transformers. BOUCHER, C. P., 1484, Crescent Street, Montreal, Canada. Jan. 22, 1934, No. 2215. [Classes 38 (ii) and 38 (iv)] Luminescent electric discharge tubes are connected in parallel to each other to the secondary windings of a high leakage transformer in order to prevent excessive current flow through any one tube. Tubes 10, 11, 12, 13 are connected each to two secondary winding sections of a set of four sections 21, 22, 23, 24 of the transformer 17. The primary windings 15, 16 of the transformer are supplied from a source 14 through a resistance 20. Capacitative elements 32, 33, 34, 35, are connected between the respective secondary windings 21, 22, 23, 24 and the common conductor 30 which is grounded at 31. The secondary windings are so arranged that the mid-point of the two secondaries supplying each tube is grounded through the capacitance elements, it being required only to insulate for half the maximum applied potential. The high leakage transformer 17, Fig. 2, has its windings mounted on the single central leg of the core 25. Magnetic shunt core sections 25d, 25<e>, 25<b>, 25<g> are interposed between the central leg 25<b> and the outer legs 25<a>, 25<c> leaving a short air gap at each end. As the currents in the transformer secondary windings tend to increase due to ionization of the tubes, the magneto motive forces due to these currents increase and the magnetic flux along the central leg 25b is constrained to pass along the magnetic shunts 25d, 25<e>, 25<f>, 25<g> thus detracting from the amount of magnetic flux flowing through the mid portion of the central core leg 25b. There is then a reduction in the total flux linking the primary and secondary windings and a consequent reduction in the potential applied to the tubes, limiting excessive flow of current in the tubes. Reduction of the instantaneous value of the potential is also achieved by the action of the impedance element 20 in the primary circuit. An increase in the amount of primary current raises the potential across the impedance 20 and lowers the potential across the primary and secondary windings. Similarly the capacitance elements in series with the tubes reduce the potential applied to the tubes upon rise of current therethrough. Modifications in the arrangements of the windings on the transformer core are described. The application to a transformer having an uneven number of windings is also described.