HID Electronic Ballasts & Lamps

Definition High Intensity Discharge (HID) lamps produce light by striking an electrical arc across tungsten electrodes housed inside a specially designed inner glass tube. Building Use highrise office institutional retail arena parking garages food service warehouse & industrial residential Building Type new retrofit Development Status prototype (electronic ballasts paired with ac to dc lamps) new (residential applications and electronic ballasts) mature (lamps and magnetic ballasts) Description High Intensity Discharge (HID) lamps produce light by striking an electrical arc across tungsten electrodes housed inside a specially designed inner glass tube. This tube is filled with both gas and metals. The gas aids in the starting of the lamps and the metals produce the light once they are heated to a point of evaporation. HID lamps produce a large quantity of light in a small package in comparison with incandescent and fluorescent sources. HID lighting is typically used when high levels of light are required over large areas and when energy efficiency and/or long life are desired. More recently, however, HID sources, especially metal halide (MH), have been used in small retail and residential environments. MH lamps produce a white light, while high pressure sodium (HPS) lamps produce a yellow light. Recent research has shown that the white light produced by MH lamps can allow people to see in greater detail than yellow light, especially in lower level lighting conditions. The 400W metal halide lamp, a very common lamp for warehouse, warehouse-retail, arena, atria and exterior applications, has an energy saving option in the 320 W or 360 W standard output or 400-watt high output versions. These options can provide about 15% to 25% energy savings for the same amount of light (320 W and 350 W options), or 10% more light (400 W high output option) for the same energy use. Like fluorescent lamps, HID lamps require a ballast to start and to maintain their operation. There are numerous ballast types designed for use with HID lamps, each offering different advantages and drawbacks. Recently, electronic ballasts have been used with lower watt HID lamps (primarily 35-100W MH). These ballasts provide an energy savings over magnetic ballasts of 8 - 20%. They also have the advantage of lighter weight, which can be important in some applications, such as track lighting. For further energy savings and light output control, the technology can be used with multi-step or continuous dimming control gear. Note that colour is compromised when HID lamps are dimmed, especially when MH lamps are dimmed below 60% (colour shifts toward blue-green) and when HPS lamps are dimmed below 40% (colour shifts towards yellow). Some lamp manufacturers will limit their warranty if lamps have been dimmed (investigate before purchasing.) Most HID lamps respond to dimming controls more slowly, sometimes taking several minutes to adjust their output. Some smaller lamps will respond immediately. HID lamps may be clear or phosphor coated on the inside wall of the outer lamp shell. Clear lamps are best when a more precise beam of light is required. Phosphor coated lamps will diffuse the light more and will reduce the colour temperature by about 300?. Recently, lamp manufacturers have introduced coloured metal halide lamps. This colouring is achieved by using a single element metal in the arc tube to produce emitted colours such as blue, green, pink and yellow. No colored phosphor or filter is used or required. Benefits increases energy efficiency in lighting provides many choices in controls and adjustability. slightly higher lamp output longer lamp life better lumen maintenance lighter weight and compact size Application Most metal halide lamps are designed for a specific burning position; these may be base up, base down, or horizontal burn only. Some lamps are designated for universal burning position, however, there may be lumen output sacrifices associated with this type. There are several arc tube designs for MH technology. These are formed, pinched and shaped. Recent experience has shown that formed arc tubes can allow universal burning positions without compromise to lamp output. This design can also have the benefit of better colour uniformity (due to uniform wall thickness providing more consistent halide cooling rates), shorter lamp warm up and re-strike periods (due to higher pressure gas fill), longer life (due to decreased electrode damage), colder starting temperatures (down to 40oC), and better lumen maintenance (light output over time - due to all above characteristics). Cost It is difficult to compare the cost of an HID lighting system to another type of system (fluorescent or incandescent), as the performance and characteristic differences are so great. When comparing energy saving lamps or high-output lamps to standard output lamps, initial cost may be higher (however, large quantities may negate cost difference) but energy savings is approximately 15% to 25% for the energy saving lamps and fewer fixtures may be required with the high-output lamps. Currently, HID electronic ballasts are more than double the cost of their magnetic counterparts. However, manufacturers are presently introducing prototype electronic ballast/lamp systems that are more comparable to the magnetic systems.