Types of Light Sources

Editor : Optomon

 Light Sources are mainly of three types: Incandescent lamp, Arc Lamp, Discharge Lamp. On this article, we are going to talk about lamps which are commonly used in photovoltaics.

Tungsten Halogen Lamp

 Tungsten Halogen Lamp has a certain amount of halogen gas and the gas produces a halogen cycle which redeposits tungsten back onto the filament, preventing darkening of the envelope and this increases lamp life as a result. Because halogen cycle actively functions at high temperature, the bulb is made of quartz which is very strong against heat.

Fig 1. Tungsten Halogen Lamp and its spectrum

Xenon Short Arc Lamp

 Xenon Short Arc Lamp produces very bright and bluish light by sparks between tungsten electrodes in a bulb filled with xenon gas. Because the lamp is at extremely high pressure, it could be exposed to risk of explosion.

Fig 2. Xenon Short Arc Lamp and its spectrum

Hydragyrum Medium-arc-length Iodide Lamp

 This lamp, also known as Metal Halide Lamp, is similar to Xenon Short Arc Lamp but much safer because the lamp uses mercury or argon gas at lower pressure. It produces high color temperature at 5,600K and takes about as short as 10 seconds or as long as 3 minutes depending upon lamp type.

Fig 3. HMI Lamp and its spectrum

Electrodeless Discharge Lamp

 Electrodeless Discharge Lamp does not have electrodes (filament) and has long lifetime. Because of that, labor cost and material cost for maintenance can be reduced. Also, it can reduce eye strain, prevent accidents, give better color classification which can improve working environment and increase productivity due to its superb color rendering. Besides, it has high efficiency and excellent luminous flux stability which takes less than 1 minute until reaching over 90% of its luminous flux.

*Magnetic Ballast

 HMI lamp repeats two times of light on and dark during each one cycle and 120 times of light on and dark per second. This changes cannot be recognized by human eyes but can be detected by a camera unless the camera is not configured precisely to this time interval per hour.

*Square Wave Electronic Ballast

 This is a ballast stabilizer which can resolve flickers. This ballast stabilizer enables producing continuous light and this remove necessity of setting frame speed to frequency of AC power. This is made possible by using transformed square wave from sine wave of AC power and this makes energy supply steady and has high tolerance against voltage and hertz. For example, when supplying voltage for electronic ballast with 120V rated voltage changes in the range of 95~132V, it does not affect hertz or color temperature of the lamp. So, this ballast can supply steady hertz and stabilized voltage to a lighting fixture and this increases brightness by 6~8% and extend life time by 20%. Also, it is much lighter than magnetic ballast. Disadvantage of electronic ballast is the fact that it makes noise compared to other devices.

To be continued on March issue…