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INTRODUCTION
RF light sources follow the same principles of converting electrical power into visible radiation as conventional gas discharge lamps.
The fundamental difference between RF lamps and conventional lamps is that RF lamps operate without electrodes.
RF LIGHTING
RF lamps, appeared about 100years ago, a half century before the basic principles lighting technology based on gas discharge had been developed.
DISCHARGE TYPES
Capacitive RF Discharge Inductive RF Discharge Wave –Sustained Discharges
Capacitive RF Discharge
The voltage applied to the lamp is mainly dropped in the sheaths.
Inductive RF Discharge
power transfer efficiency = Pp/(Pp+Pc)
operate over a wide range of gas pressure and frequency for which L.
CHOICE OF FREQUENCY AND DISCHARGE TYPE the frequency rage between 2.2 – 3.0
MHz (2.65MHz is standard) has reduced restrictions on EMI.
For frequencies at a few tens of kilohertz., generator efficiency is rather high.
COMMERCIAL RF LIGHT SOURCES
Microwave- Powered Sulphur Lamps Spherical External- Coil Induction Lamp Re-entrant Cavity Induction Lamp Self- Ballasted Re-entrant Cavity Lamp Low- Frequency Extended-coil Induction
Lamp
Microwave- Powered Sulphur Lamps
life rating of 15,000 hr.
low infrared and ultraviolet emission
good colour stability
SPHERICAL EXTERNAL- COIL INDUCTION LAMP
induction coil wrapped around the lamp
screen cage surrounds the lamp
operate at 27 W
efficiency is 37 lm/W
RE-ENTRANT CAVITY INDUCTION LAMP
operating at 2.65MHz
available in three wattages –55W, 85W,and 165W
shaped standard incandescent lamps
100,000-hr average rated life
SELF- BALLASTED RE-ENTRANT CAVITY LAMP
lamp power is 23 W at 48 lm/W
operating at 2.65 MHz
lamp life is rated up to 15,000 hours
LOW- FREQUENCY EXTENTED-COIL INDUCTION LAMP
consist of a 5.4 cm diameter Pyrex glass tube
operating frequency of 250 kHz
minimizes the problems associated with EMI
ballast design is much simpler than an RF system working at 2.65MHz
ADVANTAGES Absence of electrodes. Maintenance is low. Gas pressure is optimized for
maximal efficiency in RF lamps. It have instant and harmless
starting. Efficiency is high.
DISADVATAGES Cost is higher than fluorescent lamps. With increasing frequency, efficiency
will decrease, It is woks efficiently for some particular
frequencies, if frequency changes there are problems with electromagnetic interference (EMI).
FUTURE SCOPE
Induction lighting is an economical choice for many plants.
Induction lamps are suitable for a range of installations, including general lighting within a plant, as well as out door areas.
CONCLUSION
The elimination of electrodes opens up great opportunity for increased durability, light output and efficiency.
It removes many of the lamp-shape restrictions of conventional electrode discharge lamps .
