Metal halide (MH) lamps are available in low, mid-range, and high wattages from 35 to 2000 watts (W). Mid-wattage MH lamps range from 175 to 400 W. All major lamp manufacturers offer MH lamps in this range, commonly in wattages of 175, 200, 225, 250, 300, 320, 350, 360, and 400.Metal halide (MH) lamps, as with all HID lamps, use a ballast to regulate circuit conditions – voltage, current, and waveform – for starting and operating the device.
establish an electric arc through the lamp
limit current through the lamp after ignition
compensate for variations in line voltage and ensure consistent lumen output
MH lamps are a type of high-intensity discharge (HID) lamp that offers long lamp life, high efficacy, and good color rendering properties. In general, they are energy efficient and allow for good optical control. These qualities make them attractive for applications such as retail establishments, where both low operating cost and good light quality are important. Because of their long life, MH lamps are also appropriate for buildings with high ceilings and other facilities in which lighting is constantly in use for many hours at a time. They are popular choices for high-bay and low-bay industrial operations, warehouses, street lighting, and stadium and sports lighting. Like other gas-discharge lamps, all MH lamps require a ballast to operate.
MH lamps provide white light in a variety of correlated color temperatures (CCTs) ranging from 3200 to 5200 Kelvin, and are commonly available with a color rendering index (CRI) of 65 to 70, but can also have a CRI of 90 or above. They are superior in color characteristic to most high-pressure sodium (HPS) and mercury vapor (MV) lamps that have lower CRI values.
MH lamps compete with HPS lamps for outdoor applications such as streetlights, roadway lights, security lights, and pedestrian walkways. HPS lamps provide more photopic lumens per watt, but the whiter light of MH lamps provides better peripheral visibility at low illumination levels.
When lamps are cold, the
core and coil ballasts operating voltage may not be enough to create an arc and rely on two primary starting methods: probe-start and pulse-start.
Traditional MH lamps use probe-start,
magnetic ballast technology, which employs the use of two operating electrodes and a third, starting probe electrode in the arc tube.
Probe-start ballasts start lamps when it discharges a high open circuit voltage between the starting probe and one of the operating electrodes. Once the lamp is started, a bi-metal switch shuts off the starting probe electrode from the circuit.
Market demand for probe-start ballasts began to wane once industry realized the third electrode and other moving parts such as the switch led to inconsistencies in the lamp’s lumen and color output over their lifetimes.
The development of pulse-start electronic and electromagnetic ballasts, which create arcs by generating a high-voltage pulse using a circuit called an igniter, also moved industry away from probe-start ballasts.
Benefits of pulse start Metal Halide lamps
A metal halide lamp using an
electronic ballast is about 70% more energy efficient than typical standard HID electromagnetic ballasts with probe-start metal halide lamps.
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