Electrical lighting systems, their installation and maintenance
ELECTRICAL lighting systems form part of the Electrical and Installation Maintenance ( EIM) lesson in high school. Considering the type and quantity of loads placed into most facilities, one fact becomes clear: The lighting system is one of the most pervasive of the electrical loads.
Lighting can create l ocalized electrical field problems and affect susceptible electronic equipment. In this article, some of the issues associated with electrical noise (both conducted and radiated) that lighting systems can generate is discussed.
Do you know what the typical lighting scenarios are? Field installation guides for computer systems frequently contain warnings that advise users to avoid powering fluorescent lighting systems from the same panel boards that supply power to computer systems.
In large facilities, it’s unusual to find lighting systems powered from the same electrical panel that serves computer equipment, since lighting systems are often powered from 480/277V, threephase, four- wire systems. However,
you can’t say the same for small office environments in which 208/ 120V, three- phase, four- wire is the sole power source configuration. Even if the 480/277V and 208/120V systems are separate, installation problems may enable coupling between the power systems. This holds true with television receivers (i.e., ABS-CBN TV Plus box), auxiliary equipment, VCR, and home theater that are affected, or will cease to function at some point due to lighting system or merely with the presence of quite a high-powered/ voltage fluorescent lamp.
There i s also the conducted interference lighting system. While energy usage is certainly important from a cost perspective, the power signature of lighting systems is equally important, but from an electromagnetic compatibility standpoint. Older fluorescent lighting systems used ferroresonant ballasts, which were not extremely efficient. Also, the power factor of their current draw was often quite low.
And there is also the so- called radiated interference. Whereas the old ferroresonant ballast relied on a saturating transformer for regulation of lamp current and voltage, today’s modern electronic ballast rectifies the applied AC voltage and then supplies the lamp with high-frequency voltage from pulse-width modulation (PWM) inverters.
As a result, a high- frequency electrical field, which matches the applied voltage f rom the PWM inverters, develops at the fluorescent