GB670680A - Improvements in or relating to electrical apparatus comprising saturable chokes - Google Patents

Abstract

670,680. Supply systems for consumption apparatus. CENERAL ELECTRIC CO., Ltd., and WILLIAMS, C. E. Oct. 13, 1950 [Oct. 13, 1949], No. 26327/49. Class 38 (iv). An electric apparatus such as a discharge lamp dimming device has a variable reactor comprising series connected high and low impedance chokes arranged for progressive saturation wound on separate cores and a switch to short-circuit the former choke when fully saturated. As shown, the respective chokes 9, 10 have A.C. windings 7, 8 seriesconnected in the supply from the main secondary winding 6 of a transformer 5 to two seriesconnected low-pressure mercury vapour lamps 15, 16 whose filamentary electrodes 13, 14, 17, 18 are supplied by transformer secondary windings 19 ... 22. The choke D.C. saturating windings 30, 42 are connected to switch contacts controlled by the wiper arm 36 of a rheostat connected across D.C. supply terminals 31, 32, whereby, starting in the unsaturated position shown, corresponding to minimum discharge current, the arm 36 is rotated anticlockwise to decrease the resistance 37 until core 28 is fully saturated, whereupon contacts 23, 24 make to short windings 7, contacts 33, 34 break to de-energize winding 30, and contacts 46, 47 make to energize saturating winding 42. Rotation of arm 36 over resistance 43 saturates the core 40 until the circuit impedance is a minimum and maximum discharge current flows. In a modification a single lamp is connected directly across the supply.