17.11.2007
An explanation on the use and specifications of different halogen lamps
DICHROIC HALOGEN LAMPS (MR16 and JCD)
The code of “MR16 “ stands for Multi Reflector 16 ( diameter 50mm as it is 16 x 1/8 of an inch = 16 x 3,17mm) These lamps are made in 12V and 220V and, in theory, can be made in every other voltage if demand arises. The 12V and 220V represent thus the main market-demand.
The 12V lamp will, in most cases, be used in a fixture connected to a transformer, which will transform the mains voltage of 220V back to the 12V for which the lamp is designed.
In the lamp-world it is general knowledge that lamps are of better quality the lower the voltage is and the higher the power-consumption (W). In other words the 12V lamp is much stronger than the 220V lamp because the filament in the lamp is much thicker than the filament of the 220V lamp.
This is based on the formula V = I x R i.e. Voltage = current x resistance. The thicker the filament the lesser the resistance, thus longer life. Both lamps will be made mainly in 50W so that the wattage will not make the difference in quality.
Use of the 220V lamp has the advantage that no transformer will be needed (cost saving in installation) but the life of the lamp at 220V will hardly reach 1.000 hours whereas the 12V lamp will be made with life span of 2.000 to even 5.000 hours depending the quality of materials used. People who are saving money in not using a transformer will thus later pay more in the cost of replacement of lamps.
The lamps can be made with and without the glass-cover on top.
The cover has many advantages of which I mention:
· More safety as there is a very small risk that a halogen lamp can explode. (For instance when the 12V lamp is used at 220V by mistake)
· The lamp remains more bright as no dust can go inside the reflector
· The cover is also used to filter the Ultra-Violet radiation coming from the lamp.
Lamps can be made with horizontal filament (C-2R) but vertical (axial) is better as it allows the better focusing of the filament in the centre of the reflector. The light-beam coming from the reflector is thus more controllable in a certain direction like wide beam, medium beam or narrow beam. (38 degrees; 24 degrees and 12 degrees)
There are different ways to coat the reflector.
The main difference found is that the coating can be dichroic with result that the heat of the lamp is absorbed to the rear which creates a longer life as the lamps remain cooler or the coating can be aluminised with effect that all the heat will be radiated forward in the beam of light resulting in more intense light but shorter life as the ambient temperature of the lamp will be that much higher.
When choosing a fixture for these lamps it is thus important to know whether you operate an aluminised lamp or a dichroic lamp as the materials of which the fixture is made have to be resistant against the different temperatures that the lamp will radiate from the rear.
The lamp can also be coated with very special techniques to filter certain wavelengths of the light, which results in different colours of lamps. In this way they can be provided in PURE WHITE, or in any colour like red, green, yellow, blue etc.
Especially the PURE WHITE is interesting as the effect of this pure white goes well together with the pure white light of other types of lamps like the fluorescent lamps. This pure white is especially loved by people in countries near the Equator where people’s eyes are that much used to the intense sunlight in these hot countries.
Lamps in these colours are much more expensive as demand is relatively small and manufacturing expense is higher.
Dichroic lamps also called as “cool beam reflector lamps” were originally developed for the film industry as the light source in film-projectors. The heat radiated by the lamp would harm the film and the cool beam was therefore the solution. One day a light-architect thought what a nice small and powerful light-source the lamp is and designed a lighting fixture for it. In those days the cost of such kind of lamps was about US$ 15 and now they are relatively cheap with a world demand of more than 500 million pieces per year!
Similar lamps but in much smaller demand are the MR 11 (diameter 35 mm as it is 11 x 1/8 of an inch = 11x3, 17mm)
The major market is lamps in 50W but also demand exists in 20 and 35W.
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HIGH VOLTAGE JDR LAMPS
These lamps are basically the same as what I have explained about the MR 16 lamps here above.
The difference is just that a normal MR 16 lamp has two pins connection (GU 5.3) and the JDR lamp connects the MR 16 lamp to any kind of lamp-base. To protect the base against the heat there is a porcelain device mounted in between them.
For good quality there should be a fuse in the base and it is possible to mount some electronic components inside to improve on lamp-life like a resistor that can protect the lamp against the very high inrush current that occurs a fraction of a second when the lamp is switched on.
The common types are thus made with normal lamp-sockets like the E27, E14 or E26 base and the B22 or Ba15d base. The E stands for EDISON which is screw and the number stands for the diameter, so E27 is screw-base with a diameter of 27mm. E26 is only used in the USA and Japan.
The B stands for Bayonet which is the base with two pins at the side, the lock-in system, the number stands again for the diameter.
Some new and special bases now exist like the GU 10, which will fit in fixtures that are suitable for a DICHROIC type of lamp (fixture is heat-resistant) or the GZ 10 base, which will fit only in the fixtures designed for aluminised lamps (fixture can not resist the heat of the lamp). Obviously the lamp with GU 10 will not fit the socket designed for GZ 10 but the GZ10 will fit into the socket designed for GU 10.
These kinds of lamps can be used in any burning position.
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LINEAR HALOGEN LAMPS
One of the first halogen lamps that came to the market was the linear halogen lamp. The lamp was kind of spectacular because of its small size, and the halogen operating at very high temperatures, which allowed a lot of light to come out of this small light-source.
This development was possible because of the very high melting temperature of the quartz glass that it is made of compared to the melting temperatures of previous invented lamps which are only made with soft glass or hard glass with much lower melting temperatures.
The higher temperature at the filament makes it possible to reach more light (lumens) for every Watt of energy put in. Just the quartz glass is not enough but it is also the “halogen cycle” that is a need to make this possible.
In short the halogen cycle is a chemical process whereby the molecules that are leaving the filament when it is lighted up will return to the HOTTEST spot inside the lamp and that is –again- the filament itself.
So, the filament remains thick and robust creating the longer life even when that filament is kind of over-loaded. In normal incandescent lamps which are not filled with the special halogen gasses the molecules of the filament will go to the COLDEST spot and that is the inner wall of the glass. The filament therefore gets thinner and will eventually break which is the end of lamp-life. This phenomenon also explains why you see normal lamps getting dark at the glass. This is called the “darkening – effect “.
Since halogen-lamps provide about double light (lumens) for the same energy (Watts) they are also considered to be a kind of energy saving lamps.
In years of development many cost-savings have been possible. Now good quality halogen-lamps can be made with glass of only 9mm diameter which was still 12mm a couple of years ago.
Twenty years ago these kinds of lamps would cost about US$ 20 a piece and nowadays an average price of US$ 2 only is a common market price.
The lamps exist in different lengths:
· 78mm length in 60-100-150 and 200W
· 118mm length in 100-150-200-250-300 and 500W
· 189mm length in 750 and 1.000W
· 254mm length in 1.500W
· 333mm length in 2.000W
Normal lamps are nowadays available at low cost for a reasonable quality.
These kinds of lamps are made in mass-production.
PROFESSIONAL QUALITY for the more HEAVY DUTY applications where there is demand for LONGER LIFE, HIGHER LUMENS, and UNIVERSAL BURNING POSITION, differs from lower qualtity.
The differences are:
· Manufacture with cc-coil (coiled-coil) filaments which provide MORE LUMENS and which are stronger (thicker)
· Concaved glass as to hold the supporting rings better in place
· Silver plated contacts in the base to avoid corrosion and rusting
· Extra doses of bromide gas for better performance
· Triple support rings to keep the filament in place
Most linear halogen lamps are used in floodlight-fixtures but similar lamps are also used as heating lamps in the printing industry and in photocopy machines
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BI-PIN HALOGEN LAMPS
One of the smallest types of halogen-lamps in the market.
The most popular specifications are: With G4 base in 12V 20W (and a little in 5W and 10W)
With G6.35 base in 12V 50W (and a little in 100,150 and 250W)
There is an increasing demand for the lamp in 220V 50W for those applications where the market can accept the fragile life of the lamps most not reaching 1.000 hours.
The number behind the G indicates the distance in mm between the two pins.
A G6.35 means bi-pin with 6.35mm distance between the two pins.
GY 6.35 stands for the same lamp but with thicker and solid pins.
The G4 lamp is used to assemble the MR 11 lamps as above in DICHROIC HALOGEN LAMPS (MR16 and JCD).
The GY6.35 lamp is used to assemble the MR16 lamps as above in DICHROIC HALOGEN LAMPS (MR16 and JCD).
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AUTOMOITIVE HALOGEN LAMPS
There is a huge demand of automotive halogen lamps especially in developing countries where cars are a kind of luxury and people spend time and money in improving the performance of the car including the lighting.
The bi-pin lamps that are used to produce MR 16 lamps can also be used for the manufacture of H3 automotive lamps but with some other specification of more light and shorter life.
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