| 摘要 |
PURPOSE:To restrict the variation of the light color of a lamp within a narrow range, and obtain a lamp causing no flickerings even when it is used with a low source voltage of 200V grade by diffusing the heat of an arc spot and preventing any over heat of the extreme end of an electrode by using a hollow electrode, which has a wide area at its end, as an upper electrode. CONSTITUTION:A metal halide lamp of 100W is illustrated in the figure. A hollow-type electrode used as an upper electrode, and a projection-type electrode used as a lower electrode are installed at both ends of an oval emission tube 7. The outer surfaces of the tube 7 which are near the above electrodes are coated with heat insulating films 8. In addition, an auxiliary electrode is provided at one end of the tube 7, and reverse electric potential is applied to the auxiliary electrode by means of a starting resistance 9 of 20kOMEGA. Acording to this invention, by the combination with a single-choke-type ballast of 200V grade which is economical and is most widely used throughout the country, a lighting device for a metal halide lamp which has a low extinction voltage of arc, an excellent luminous- flux maintenance rate and a suppressed flickering can be obtained. |
