Measurement of Power Delivered to Rapid Start Fluorescent Lamps and other Multi-Port Devices

Abstract

The standard method used to measure total power delivered to a rapid start fluorescent lamp requires separate sources for arc and cathode power. While this method is suitable for reference photometry, it cannot be applied to lamps operated by a commercial ballast. With the increased emphasis on energy efficient lamp and ballast systems, a method is needed to measure ballast loss and lamp power in commercial systems using both 60 Hz core-and-coil ballasts and high frequency electronic ballasts. In this report, a method is developed for measuring the power delivered to rapid start fluorescent lamps or other multiport loads. It is shown that the power delivered to any N terminal device may be determined by summing N-1 two terminal power measurements. For each measurement, the current channel of the wattmeter is connected to measure the current flowing into the nth terminal (n = 1 to N-1) while the voltage channel is connected to read V_n – V_N where N is the designated common terminal.