On the Voltage Allotments in Hot-Cathode Fluorescent-Lamp Circuits

Abstract

It plays an important roll in the selection of fluorescent-lamps and their series ballasts to determine the voltage allotments in the hot-cathode fluorescent-lamp circuits. Problems are confined to the conventional low power factor lamp circuits, inductive ballasts in series. Lamps having several different arc gap lengths and outer diameters, and ballasts capable to vary their iron core sectional area and number of turns are used for following measurements.The effective values of sinusoidal line voltage, lamp terminal voltage and ballast impedance drop are designated as UN, UL, and UR respectively. Some relations, between these voltages were investigated by R. F. Hays and D. S. Gustin experimentally and H. Stranch theoretically, but these results cannot be applied satisfactorily to many actual cases.Combining several kinds of lamps and ballasts, following results are obtained in the wide range of lamp currents.UL+UR=(1.23±0.03)UN(3)By keeping a lamp current constant and varing the UR/UN values, nearly constant lamp voltage UL is obtained for large UR/UN value, except steep increase at a critical value of UR/UN. From these experiments, the next condition is derived.UR/UN>0.58±0.02(5)In accord with the variation of line voltage UN, the lamp current I varies following the lamp and ballast characteristics. Now the so-called current variation Re is defined by the next equationThe relation between UR/UN values and Re shows that Re increases steeply at a critical value of UR/UN. From these conditions, UL/UN<0.57±0.02(6)can be obtained. When UR/UN<0.66, the lamp terminal voltage wave form has a steep peak-head and the current wave form tends to have some pausal durations. From equation (3) and (6), (7)is obtained. Fquations (3), (6) and (7) are desirable conditions for the lamp life and ballast design.From these relations we can obtain the methods of deciding the lamp length, the design of ballast capacity and many other conclusions.