linsheng explains: High-intensity discharge (HID) lamps offer many advantages for a wide range of lighting applications, even as the LED lighting revolution continues to grow rapidly. Although subsequent regulations allowed the use of special ballasts, the Energy Policy Act of 2005 eliminated the manufacture and import of mercury vapor (MV) ballasts, making the MV system obsolete. The lighting industry can foresee that the Congressional Legislation or Department of Energy (DOE) rulemaking action will eliminate MV manufacturing lights. The remaining two HID lamp types are metal halide (MH) and high pressure sodium (HPS) sources, and almost all current technology development and market potential are concentrated in the MH source.

　　Technical snapshot

　　The MH lamp consists of an arc tube surrounded by an outer bulb envelope that isolates the arc tube from the environment and blocks any UV radiation. The arc tube is made of quartz or ceramic glass and contains a mixture of argon, mercury and metal halide salts at a color temperature of 1,800 K to 10,000 K and a color rendering index (CRI) of up to 98.

　　Usually unaffected by ambient temperature and equally suitable for extreme temperatures, MH lamps can achieve an average rating life of up to 24,000 hours and an output of 1,200 lm to 200,000 lm. The maximum practical power of the "white light" MH lamp (80CRI) is about 230 lm / W. Like all arc lamps, the MH lamp requires a ballast to provide the start voltage for the lamp, current limit during warm-up, and is provided during operation. Constant current. As the lamp heats up, the current decreases as the voltage and power increase. Eventually, the lamp AC voltage is stable and the lamp power is adjusted to an appropriate level.

　　Repression ballast

　　The efficiency of the traditional magnetic MH core and coil ballast is greatly improved, and its efficiency is 88%. It is a solid electronic ballast or electronic ballast with an efficiency of up to 97%. E-ballast uses high frequency or low frequency square wave systems and other advanced waveforms to provide higher lumen maintenance, longer life, fault mode protection and better power regulation. It also allows for continuous dimming, better color control, and no stroboscopic effect. The open circuit voltage requirements of the ballast are reduced to the lamp's operating requirements, thereby reducing ballast operating temperatures, extending ballast life, and reducing maintenance/replacement costs.

　　The original method for starting the MH lamp is called a probe starting method, which uses an operating electrode at each end of the arc tube and a starting probe mounted near one of the operating electrodes. In order to start the lamp operation, a discharge is generated on a small gap between the starting probe electrode and the nearby operating electrode; finally, an arc current is generated between the two operating electrodes, and the bimetal switch is removed from the circuit. Needle electrode. Tungsten is sputtered from the electrode each time the MH lamp is turned on. Over time, tungsten deposits cause the walls of the arc to darken, thereby degrading the performance of the lamp.

　　A major improvement in MH lamp operation is a pulsed arc tube that uses a igniter within the ballast to deliver a high voltage pulse directly on the electrode to activate the lamp. By eliminating probes and bimetallic switches - components that are generally prone to failure - pulse-start lamps have many advantages, such as increased lumen output.

　　The Energy Independence and Security Act of 2007 eliminated probe-starting ballasts in the new 150W to 500W MH luminaires, so the only choice for this power range is the pulse-start lamp, using quartz or ceramic (polycrystalline alumina) arc tubes It is often referred to as a ceramic or CMH lamp (similar to an HPS arc tube). The ceramic MH arc tube is five times shorter than the HPS arc tube and is about half the length of the quartz arc tube.

　　Ceramic MH lamps are available in a variety of configurations, including PAR20, PAR30, PAR38 and T6, providing greater light output, improved color rendering and limited color cast compared to probe start lamps.

　　Most MH lamps are designed for specific combustion locations, such as horizontal, vertical pedestal up or vertical pedestal down, which can result in severely shortened lamp life, lumen output, and color changes when operating in unspecified combustion locations. .

　　Vertical position spiral MH lamps are mainly used for downlights. Horizontal position spiral MH lamps typically have arcuate arc tubes and use position fixing pins in the base, referred to as pre-focus or position-oriented large bases (POM). The base and mating socket ensure proper positioning of the lamp. Since these lamps are primarily used for outdoor lighting, the minimum power available is 175W. A special version of the logo and sports lighting is also available.

　　The "universal" position light is the most versatile type; however, it is about 10% less light output than a position-specific lamp and has a more limited color temperature range.

　　Security issues and NEC

　　Due to its high operating temperature (900 ° C to 1,100 ° C), the pressure of the chamber is 5 atmospheres to 30 atmospheres, and the MH lamp may be broken by the arc tube. If the arc tube ruptures, hot particles may be ejected from the bulb. Typically, all MH lamps passively reach their end of life. However, MH lamps that operate continuously without shutting down experience arc tube rupture, although this rarely occurs. The manufacturer recommends a group change at or before the end of the evaluation life, rather than on-site replacement.

　　Some manufacturers offer automatic cycle controllers that can be as simple as a clock, using an arranging schedule or randomly turning the light system on and off.

　　In response to the possibility of MH lamp rupture, the National Electrical Code (NEC) of 2005 included specific rules for MH luminaires (except for thick glass PAR lamps), requiring them to be either closed or have some physical means to ensure that only O-lamps can be used. The O-lamp has a protective glass casing above the arc tube. According to UL 1572 and CSA C22.2 No. 9.0, E-type lamps can only be used in properly rated enclosed luminaires. Finally, when the lamp is operated in a near vertical position, the S-lamp is limited to a specific model in the range of 350W to 1,000W, in open luminaires. All listed fixtures have light/relay information on the label attached to the fixture, showing the specific bulb used

　　Any power interruption, even a severe voltage dip in several cycles, can cause the MH lamp to lose arc conduction, and the lamp takes a few minutes to restart because the arc tube must be cooled and the internal vapor pressure must be reduced to the point where the arc can be struck again. This restart time and warm-up time can result in a delay of up to 15 minutes before returning to full-light output.

　　To solve this problem, NEC needs some form of backup lighting system, such as an integrated tungsten halogen lamp connected to the emergency power supply, if the power supply is temporarily interrupted to certain HID lighting systems. In addition, ballast assemblies known as thermal re-arcing devices can be specified for certain single-ended and double-ended MH lamps. Therefore, after an instantaneous voltage dip, the hot restart accessory can restart the arc of the MH lamp almost immediately.

　　Control the future

　　Since the list of mandatory control requirements increases with each version of the ASHRAE / IESNA 90.0 standard, the control functions (wired and wireless) are inserted into the MH luminaire to change the lumen output (eg, 50% reduction) based on the input of the occupancy sensor, the switch Or some other input, such as scheduling software, to produce a cost-effective strategy.

　　Clearly, by expanding the use of MH lamps and actively pursuing further efficiency milestones, significant energy savings can be achieved.

　　SIDEBAR 1: Next Generation Energy Issues

　　Many commercial building energy regulations have energy-saving rules for outdoor lighting. For example, ASHRAE / IES 90.1 2010, IECC energy-saving codes and some model regulations require outdoor HID ballasts to have some type of dual-level light output and/or dimming capability. In addition, the California Title 20 product regulations require 150W to 500W MH luminaires with a specific level of ballast or luminaire efficiency or with automatic energy efficient lighting control.

　　For these reasons, two-layer control systems for area or street lighting are gaining more and more applications. The nodes are installed in the top surface of the luminaire and can communicate with the central operations center via radio, satellite and/or cellular systems to communicate control and status messages to web pages. This allows the operator to control, adjust, monitor and receive maintenance messages from each luminaire on the system.

　　SIDEBAR 2: MH's improvement on the horizon

　　The Department of Energy has identified 10 subject areas where emerging technologies can improve the performance of HID sources, and some are now commercialized, such as electrodeless lamps. Continuous research on materials, coatings, arc tube shapes, electrodes, filling chemistry, lamp/ballast waveforms and thermal management should also improve MH performance. Mercury-free MH lamps are currently used as automotive headlamps; however, eliminating mercury fill results in reduced efficacy. However, the future is expected to overcome the reduction in efficacy. Some lighting industry leaders want to extend the Environmental Protection Agency's ENERGY STAR program to include HID products.

　　SIDEBAR 3: Advantages of ceramic metal halide (CMH) lamps

　　Highly controllable point source

　　• Wide range of power from 15W to 400W, oval, tubular, linear single and

　　Double end and reflector shape.

　　• The latest technological advancement of medium power ceramic MH can achieve 24,000 hours

　　Rated life, CRI up to 94, luminous efficiency of 120 lm / W.

　　• Consistent color with two color temperatures (3,000K and 4,200K).

　　• High lumen maintenance (close to 90%).

　　• CCT ranges from 1,800K to 10,000K.

　　• Smaller and lighter than comparable SSL systems.

　　• Universal burning position for most bulbs.

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