When I use photometry file of Fluorescent lamp fixture , I see sometimes that the total wattage consumption of the fixture is less than the summation of wattage rating of the lamp and the electronic ballast loss. I was told that the lamp runs in undercurrent inside the fixture due to heat generated. My question is why the current consumption ( thus wattage ) of the lamp goes down with the heat generated ? Do the heat generated affect the lumen output and CCT of the lamp ?
Thank you in advance.
I think you see that the system consumption is lower than the power of a single lamp because you use high frequency electronic ballast (such as High Frequency Performer (HFP).
For example if you take a TL-D 58W with a conventional ballast, the system power will be 66.5W but if you use this lamp with a HF ballast the system power will be only 55W (less than the lamp power) (please find attached photometrical data).
The flux of fluorescent lamp is dependant on the ambiant temperature. Fluorescent lamp with amalgam technology are less dependant on ambiant temperature.(see attached example)
In fact much of the power supplied into a conventional ballasts produces waste heat energy.
In order to improve the efficiency of a fluorescent lighting system we can reduce the ballast losses, run the lamp at high frequency and reduce losses attributable to the lamp electrodes.
With this type of HF ballast the ballast factor is close to 1.
By operating at high frequency the lamp is more efficient (in lm/W) than with 50Hz( or 60Hz).
Consequently for the same luminous flux we have lower system power with HF ballast than with conventional one.
I hope that answers your question.