Halogen Lamp & Gaseous Discharge Lamps

 Halogen Lamp

👉 Small-scale halogen (preferably iodine) vapour addition to the pressing gas

👉It uses a chemical process known as the regenerative cycle to restore some of the evaporated                    tungsten vapour to the filament.

👉Tungsten + Iodine = Tungsten Iodide 

👉Thermal breakdown of Tungsten Iodide near the filament at higher temperature results in deposition        of tungsten on filament

Advantage and Application

Advantages: 

💢Higher operating temp. &hence better Luminous efficacy (22- 33 Lu/W) 

💢 Longer life (2000 working hours) 

💢Reduced blackening of lamp 

💢Reduced dimension 

💢 Better colour rendering 

Application:

💥Outdoor Illumination of building, playground, gardens, airport runways etc. 

💥Indoor illumination of public halls, factories, sports halls, TV studio etc.

Gaseous Discharge Lamps 

👉 Sodium Vapour ↠ (a) High Pressure (HPSV or SON) (b) Low Pressure (LPSV or SOX)

👉Mercury Vapour

👉Neon

👉 Metal Halide 

👉 Fluorescent 

👉Compact Fluorescent Lamp (CFL)

Sodium Vapour Lamp

A sodium vapour lamp is a particular kind of high-intensity discharge (HID) lamp that emits illumination using sodium vapour.

The lamp works by passing an electric current through a tube containing sodium and other gases, which causes the sodium atoms to become excited and emit yellow light.

Contents:

 Construction of High Pressure Sodium Vapour Lamp
 Working Process of High Pressure Sodium Vapour Lamp 

 Electrical & Optical Characteristics High Pressure Sodium Vapour Lamp

 Application of High Pressure Sodium Vapour Lamp

 Construction of Low Pressure Sodium Vapour Lamp 

 Working Process of Low Pressure Sodium Vapour Lamp 

 Electrical & Optical Characteristics Low Pressure Sodium Vapour Lamp

 Application Application of Low Pressure Pressure Sodium Vapour Lamp

(a) High Pressure (HPSV or SON)

Construction:-

✋Commercially, HPSV is known as SON. 

✋ The creation of HPSV lamps can be used thanks to polycrystalline alumina, 

       a transparent ceramic substance. 6 HPSV lamp uses are available.

✋Ceramic (PCA) inner tube,

✋Quartz glass (Fused Silica) exterior jacket, and 

✋Sodium vapour pressure of 7000 Pa and inert gas (Xenon) pressure of 3000 Pa

Building Method

⋙ Atoms are much closer. 

⋙ On increased pressure – Spectrum Broadening due to self absorption of D lines. 

⋙ Much more levels of excitation and hence wider spectrum 

⋙ Yellowish - White Colour Output 

⋙ Leak transformer is used for high starting voltage and reduced working voltage. It 7 voltage and              reduced working voltage. It is step up transformer with high leakage reactance. 

⋙ Electronic Igniter may also be used as control gear. 

⋙ Starting Voltage – 1500-5000V , typically 2500 V for 1micro second 

⋙ Operating Temperature- 4000 K at centre of Plasma Column and 1500 K at wall. Hence. Bulb                Temp– nearly 1200 ° C

⋙ Power rating – up to 1000 W available.

Applications and Visual Properties

⋟ More continuous Spectrum than LPSV 

⋟ Yellow White Light Output 

⋟ Takes time for full brilliance and actual colour output 

⋟ CRI 20 -40 

⋟ CCT – nearly 2000 K Luminous efficacy – 60 -140 Lm /W 8 

⋟  Luminous efficacy – 60 -140 Lm /W 

⋟  Life- 12000 to 24000 working hours 

⋟  It is suitable for Outdoor Lighting – Where, efficacy is essential and colour rendering is not so               important 

⋟ Widely used in Highway, Streetlight, Parks, Rail yards etc.

(b) Low Pressure (LPSV or SOX)

Construction

⇛ LPSV is commercially known as SOX.

⇛ Generally Horizontal Configuration 

⇛ Bulb contains 2 sets of electrode normally made of tungsten in an U shaped arc tube placed within a       borosilicate glass envelope. 

⇛  Arc (discharge) tube contains metallic 3 

⇛ Arc (discharge) tube contains metallic sodium (solid when not working), neon or argon gas as                 Auxiliary gas (Penning Mixture) 

⇛ Sodium Vapour pressure – 1 Pa and inert gas pressure - nearly 1070 Pa (1 Atm pressure = 101325          Pa) 

⇛ The heat-reflective coating of indium oxide allows visible light to pass but reflects infra-red                   radiation back inside the tube

Working Process

🧿AC supply 

🧿Na should never get in contact with air to avoid explosion. 

🧿First discharge through Inert Gas (Neon/Argon, but mainly Neon) gasproducing reddish orange              radiation 

🧿Developed heat vaporises Na & which is finally ionised producing light.

🧿1 st excitation level energy – 2.1 eV. Resonance Radiation for Na is 5893 Å= 589.3 nm. (Yellow). 4        = 589.3 nm. (Yellow). (actually, 589.0 nm & 589.6 nm- D Lines) 

🧿LPSV light output is monochromatic yellow. 

🧿Operating Temp. – 300 ˚ C 

🧿Starting Discharge Voltage 400 – 600 V and Running Voltage – 165 V

🧿Power Rating – 45 -200 Watt.

Optical Characteristics and Application 

ⓄTakes 15 minutes for full brilliance in output.

Ⓞ Life – 10000 - 14000 working hours.

Ⓞ Efficacy – Very high - 140-200 Lm/W (monochromatic radiation near athighest spectral sensitivity      of human eye) 

Ⓞ Power Factor – 0.3 & after improvement improvement 0.8-0.9 

Ⓞ CRI – less than 20 (since monochromatic) even may be negative 

Ⓞ CCT – less than 2000 K 

Ⓞ It is rarely used. Normally used in Tunnel, Store where colour rendering is of low importance.

 

 ⋡ Mercury Vapour                                                      ⋡ Incandescent Lamp 

 

  ⋡  Fluorescent Lamp                                                   ⋡ Metal Halide Lamp