METAL VAPOUR DISCHARGE LAMP

摘要

PURPOSE:To obtain certain starting and enable the capacity of a thermoswitch to be small by allowing subsidiary arc discharge to be generated between main electrodes and auxiliary electrode. CONSTITUTION:Main electrodes 7 and 8 are arranged at both ends of a luminous bulb 4. An auxiliary electrode 9 is arranged in the vicinity of one main electrode 7. The auxiliary electrode 9 is connected with the lead 12 on the other side through an always closed thermoswitch 14 such as bimetal and an auxiliary resistor 13. The value of resistance of the auxiliary resistor 13 is set as follows: When the thermoswitch 14 is closed, the auxiliary arc discharge having discharge current of 1A or more is generated between the auxiliary electrode 9 and the main electrode 7. During this auxiliary arc discharge, the following relation is formed: V=2.94I+ 50, in which V is the sum of the voltage drop due to the auxiliary resistor 13 and the auxiliary arc discharge voltage between the auxiliary electrode 9 and the main electrode 7, and I is the auxiliary arc discharge current.