Characteristics of 400-Watt and 250-Watt Type H Mercury Lamps

Alternating-current arcs between oxide-coated tungsten electrodes in mercury vapor at pressures of one-half to one atmosphere have recently been developed as light sources, characterized by high luminous efficiency, long life, compact dimensions, and a high degree of simplicity in application. A 400-watt and a 250-watt lamp, designated as type H1 and type H2 respectively, are commercially available. The essential elements of the lamps and their operating equipment are described. The electrical starting and operating characteristics are explained. Wave forms showing the cyclic variation of arc voltage, current, and light output are discussed. Life, lumen maintenance, and efficiency ratings are defined.