DEPARTMENT OF ELECTRONICS & COMMUNICATION

Presented by

Ashish Dashore

E.C. Deptt.

CONTENTSCONTENTS

1.Introduction1.Introduction2. RF Lighting2. RF Lighting3. Discharge types3. Discharge types4. Choice of frequency 4. Choice of frequency

5. Commercial RF light sources5. Commercial RF light sources6. Advantages6. Advantages7. Disadvantages7. Disadvantages8. Further Scope8. Further Scope9. Conclusion9. Conclusion

INTRODUCTION

RF light source follow the same principles of RF light source follow the same principles of converting electrical power into visible radiation converting electrical power into visible radiation

as conventional gas discharge lamp. The as conventional gas discharge lamp. The fundamental difference between RF lamp & fundamental difference between RF lamp & conventional lamp is that RF lamps operate conventional lamp is that RF lamps operate

without electrodes in conventional florescent & without electrodes in conventional florescent & High Intensity Discharge lamps has put many High Intensity Discharge lamps has put many

restrictions on lamp design & performance & is a restrictions on lamp design & performance & is a major factor limiting lamp life.major factor limiting lamp life.

HISTORY RF LIGHTINGHISTORY RF LIGHTING

The very first proposal for RF lighting, as The very first proposal for RF lighting, as well as the first patent on RF lamps, well as the first patent on RF lamps, appeared about 100years ago, a half appeared about 100years ago, a half

century before the basic principles lighting century before the basic principles lighting technology based on gas discharge had technology based on gas discharge had

been developed. been developed.

DISCHARGE TUBEDISCHARGE TUBE

Discharge Tube is the device in which a gas conducting an Discharge Tube is the device in which a gas conducting an electric current emits visible light. It is usually a glass electric current emits visible light. It is usually a glass tube from which virtually all the air has been removed tube from which virtually all the air has been removed

(producing a near vacuum), with electrodes at each end. (producing a near vacuum), with electrodes at each end. When a high-voltage current is passed between the When a high-voltage current is passed between the electrodes, the few remaining gas atoms (or some electrodes, the few remaining gas atoms (or some

deliberately introduced ones) ionize and emit colored deliberately introduced ones) ionize and emit colored light as they conduct the current along the tube. The light light as they conduct the current along the tube. The light

originates as electrons change energy levels in the originates as electrons change energy levels in the ionized atoms. By coating the inside of the tube with a ionized atoms. By coating the inside of the tube with a

phosphor, invisible emitted radiation (such as ultraviolet phosphor, invisible emitted radiation (such as ultraviolet light) can produce visible light; this is the principle of the light) can produce visible light; this is the principle of the

fluorescent lamp. fluorescent lamp.

DISCHARGE TYPESDISCHARGE TYPES

There are three practical ways to energize There are three practical ways to energize RF light source.RF light source.

Capacitive RF discharge.Capacitive RF discharge.

Inductive RF discharge.Inductive RF discharge.

Wave-sustained discharge.Wave-sustained discharge.

Capacitive RF DischargeCapacitive RF Discharge

Capacitive RF discharge may be energised by Capacitive RF discharge may be energised by RF electrodes placed inside or outside the RF electrodes placed inside or outside the discharge vessel .The current path in a discharge vessel .The current path in a capacitive RF discharge plasma is closed by capacitive RF discharge plasma is closed by displacement currents in the RF electrode displacement currents in the RF electrode sheaths (whether the electrodes are inside or sheaths (whether the electrodes are inside or outside the discharge vessel). Capacitive RF outside the discharge vessel). Capacitive RF discharges operate at gas pressure considerably discharges operate at gas pressure considerably lower than atmospheric pressure and are exited lower than atmospheric pressure and are exited by an RF electric field E with frequency lower by an RF electric field E with frequency lower than 1GHz wavelength much larger than the than 1GHz wavelength much larger than the discharge size discharge size

Inductive RF DischargeInductive RF Discharge

In an inductive RF discharge, the plasma RF In an inductive RF discharge, the plasma RF current is closed within the plasma without current is closed within the plasma without forming RF sheaths. The electric field that forming RF sheaths. The electric field that maintains the discharge is induced by an RF maintains the discharge is induced by an RF current flowing through an induction coil outside current flowing through an induction coil outside or inside the plasma. Inductive RF discharges or inside the plasma. Inductive RF discharges (IRFD) or inductively coupled plasmas (ICP) (IRFD) or inductively coupled plasmas (ICP) operate over a wide range of gas pressure and operate over a wide range of gas pressure and frequency for which L.frequency for which L.

Wave –sustained Discharge Wave –sustained Discharge

Wave-sustained RF discharges (WRFD) are maintained by Wave-sustained RF discharges (WRFD) are maintained by electromagnetic waves that are incident on the plasma electromagnetic waves that are incident on the plasma surface or propagate along a plasma boundary .the surface or propagate along a plasma boundary .the wavelength in a wave-sustained RF discharge is wavelength in a wave-sustained RF discharge is comparable to the plasma size ( L), which implies a comparable to the plasma size ( L), which implies a relatively high RF driving frequency. Wave discharges are relatively high RF driving frequency. Wave discharges are usually maintained by microwave power sources at usually maintained by microwave power sources at frequency in the GHz range. However, in some surface frequency in the GHz range. However, in some surface wave discharges with a long plasma column working as a wave discharges with a long plasma column working as a slow wave structure, the length of the propagating waves is slow wave structure, the length of the propagating waves is much shorter than in a vacuum, and the driving frequency much shorter than in a vacuum, and the driving frequency may be much smaller (10-100 MHz.). The application of may be much smaller (10-100 MHz.). The application of microwaves is advantageous for the excitation of high –microwaves is advantageous for the excitation of high –pressure HID light sources where relatively high- power pressure HID light sources where relatively high- power density is needed to achieve a near –equilibrium plasma.density is needed to achieve a near –equilibrium plasma.

Choice Of Radio FrequencyChoice Of Radio Frequency

For Industrial purpose:-For Industrial purpose:-

13.56MHz, 27.12MHz & 40.68MHz13.56MHz, 27.12MHz & 40.68MHz

In microwave band:-In microwave band:-

2.45GHz2.45GHz

Commercial RF Light SourceCommercial RF Light Source

Within the past 10 years, the following RF lamp Within the past 10 years, the following RF lamp designs have achieved varying degrees of designs have achieved varying degrees of commercial use: commercial use:

Microwave power ED Sulfur LampMicrowave power ED Sulfur Lamp Spherical External Coil Induction LampSpherical External Coil Induction Lamp Re-Entrant Cavity Induction LampRe-Entrant Cavity Induction Lamp Self-Ballasted Re-Entrant Cavity LampSelf-Ballasted Re-Entrant Cavity Lamp Low-Frequency Extended-Coil Induction LampLow-Frequency Extended-Coil Induction Lamp

ADVANTAGESADVANTAGES

Absence of electrodes.Absence of electrodes.

Maintenance is low.Maintenance is low.

It has instant & harmless starting.It has instant & harmless starting.

Gas pressure is optimized for maximum Gas pressure is optimized for maximum efficiency.efficiency.

The lamp luminous can be easily The lamp luminous can be easily controllable.controllable.

Efficiency is high.Efficiency is high.

DISADVANTAGESDISADVANTAGES

Cost is higher than fluorescent & Cost is higher than fluorescent & incandescent lamps.incandescent lamps.

With increasing frequency efficiency will With increasing frequency efficiency will decreases.decreases.

More complex design.More complex design.

Maintenance is not much easy.Maintenance is not much easy.

FURTHER SCOPEFURTHER SCOPE • Induction lamps are suitable for a range of installations, Induction lamps are suitable for a range of installations,

including general lighting within a plant, as well as out door including general lighting within a plant, as well as out door areas. areas.

• Energy conservation and environmental concerns will Energy conservation and environmental concerns will inevitably bring about a new generation of compact inevitably bring about a new generation of compact residential RF lamps. Induction lighting is an economical residential RF lamps. Induction lighting is an economical choice for many plants. While it costs two or three times choice for many plants. While it costs two or three times more than a HID lamp and ballast system, induction more than a HID lamp and ballast system, induction lighting last six times longer. Payback, in maintenance lighting last six times longer. Payback, in maintenance savings alone, can be as fast as one year for hard-to-reach savings alone, can be as fast as one year for hard-to-reach applications and two to three years for general ambient applications and two to three years for general ambient lighting.lighting.

CONCLUSIONCONCLUSION

• The elimination of electrodes opens up great The elimination of electrodes opens up great opportunity for increased durability, light opportunity for increased durability, light output and efficiency, and it removes many of output and efficiency, and it removes many of the lamp-shape restrictions of conventional the lamp-shape restrictions of conventional electrode discharge lamps.electrode discharge lamps.

• The initial cost of RF lighting products is the The initial cost of RF lighting products is the major barrier to the widespread RF lamps, but major barrier to the widespread RF lamps, but with further development of the many with further development of the many components of RF lighting technology, the components of RF lighting technology, the range of applications should increase.range of applications should increase.