EFFECT OF POWER REDUCTION ON THE LIFE OF MERCURY GAS DISCHARGE LAMPS.

For physical reasons, a mercury-vapor high-pressure discharge lamp of a specific output of more than 25 w/cm arc length can only be designed for operation under defined electric and thermic parameters. In order to obtain economic lifetimes it is absolutely necessary that such a lamp be operated in accordance with the defined parameters. Any divergence from these parameters reduces the life of the lamp, even if the divergence is only for a short time. The reduction of the energy supply (half-load operation) modifies the power input of the lamp and therefore the electric parameters of the lamp operation. A reduction of the life should be expected after each power reduction. If the power is reduced by means of a dimmer, not only is there a modification of the lamp current, but also a considerable increase in the number of ignition processes per unit of time. This also affects the lifetime of the lamp.