ELECTRIC LAMPS - PART - 09 - OPERATION OF HALOGEN LAMP

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• published: 03 Jan 2016
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ELECTRIC LAMPS – PART – 09 - OPERATION OF HALOGEN LAMP INVENTOR OF HALOGEN LAMP A halogen lamp is an advanced form of incandescent lamp. 1955 Frederick A. Mosby a General Electric Engineer developed an efficient halogen lamp, and adapted the lamp for use in regular lamp sockets. 1955 - Philips Engineers developed a lamp that used the halogen bromine. In 1959, General Electric patented a commercially viable halogen lamp using iodine as the halogen gas. Halogen bulbs produce light that is whiter and brighter, use less energy, and longer life than standard incandescent bulbs of the same wattage. PROBLEM IN THE INCANDESCENT LAMP The main problem in the tungsten filament incandescent lamp is evaporation from the hot filament condenses on the cooler inside bulb wall, causing the bulb to blacken. This blackening process continuously reduces the light output over the life of the lamp. This problem gave birth to halogen lamp. The halogen lamp is a type of incandescent lamp which uses a halogen gas in order to increase both light output and rated life. Iodine and Bromine are only used in halogen lamps. It is also known as a quartz halogen and tungsten halogen lamp. CONSTRUCTION 1. GLASS BULB Depending on the type of halogen lamp, the bulb material is either quartz (fused silica) or aluminosilicate glass. Quartz glass has the appropriate temperature resistance for the tungsten-halogen cycle, which produces bulb temperatures of upto 900°F. Either glass comes in the form of cylindrical tubes that are precut to the desired length or cut to length by the lamp manufacturer. 2. FILAMENT The filament is composed of ductile tungsten and located in a gas filled bulb just like an incandescent bulb. Filaments are also oriented in two ways, axial or transverse. 3. GAS krypton or xenon – Helps retard the rate of tungsten evaporation and the gas in a halogen bulb is at a higher pressure (7-8 ATM). The higher the pressure and better filling gases extend the life of the bulb. Higher filament temperature results in better lamp efficacy. 4. REFLECTIVE COATING Halogen lamps are also designed with a special infrared reflective coating on the outer side of the bulb to ensure that the radiated heat, which otherwise is wasted, is reflected back to the lamp filament. OPERATION 1. When supply is switched ON, the filament begins to glow red as more current passes through it. 2. The temperature rapidly increases. The halogens boil to a gas at relatively low temperatures. 3. Iodine is at 184 C and Bromine is at 59 C. 4. The halogen chemically reacts with the tungsten deposit to produce tungsten halides (a salt of any halogen acid). 5. When the tungsten halide reaches the filament, the intense heat of the filament causes the halide to break down, releasing tungsten back to the filament. 6. This process—known as the tungsten-halogen cycle—maintains a constant light output over the life of the lamp. 7. Most halogen lamps range in power from 20-2,000 watts and low voltage types range from 4-150 watts. 8. Halogen lamps can be configured as single ended and double ended. 9. Double ended halogen is commonly used. 10. These lamps generally are the larger wattage lamps and are used for work lights, yard lights and film production lamps. ADVANTAGES 1. Halogen Lamps are compact in size and lightweight. 2. The halogen lamp is fully dimmable unlike compact fluorescent lamps. 3. Does not contain mercury like CFLs (fluorescent) or mercury vapor lights. 4. Better color temperature than standard tungsten (2800- 3400 Kelvin) lamp. 5. Its light is closer to sunlight. 6. Instantly switches on to full brightness and requires no warm up time. 7. The filament burns hotter and hence less wattage is required. 8. Life of halogen lamp is 2,000-4,000 hours (about two to four years). DISADVANTAGES 1. Halogen lamps can also pose a safety threat, as the heat generated can range from 250-900 F (121-482°C). [Formula for converting F – C = [F-32] / [1.8] 2. Extremely hot (easily capable of causing severe burns if the lamp is touched). 3. On, explosion, the bulb is capable of blowing and sending hot glass shards (a broken piece of a brittle artifact) outward. 4. The life of a halogen lamp is shortened by frequent on and off cycles. APPLICATIONS 1. The halogen lamp has an instant 'on' ability unlike mercury vapor or high pressure sodium, therefore they work well for security lamps that are activated by motion sensors. 2. As portable work lights and auto headlights. 3. As home Interior Lighting (Smaller Wattage). 4. In commercial Exterior Lighting (Larger Wattage). 5. Halogen lamps are used in television and film production.