Influence of frequency and current waveform on low-pressure sodium lamp operation

Efficient light production in AC-supplied low-pressure sodium (LPS) lamps is strongly dependent on plasma conditions during the complete half-cycle. Significant luminous efficacy gains are obtained with sinusoidal currents of hundreds of kilohertz or with rectangular current forms at lower frequencies. Measurements of light emission from an 18-W LPS lamp at several operating conditions between 50 Hz-20 kHz, reported in this paper, can be useful to establish a compromise between supply frequency and current waveform shape for electronic ballast design.