MetalHalideShop Glossary

Arc Tube: A completely sealed quartz or ceramic tube where the electrical discharge (arc) occurs and light is generated
Energy Master: Venture Lighting's line of Energy saving Retrofit lamps that operate on existing ballasts at lower watteges than the original lamps
Lamp Lumen Depreciation Factor (LLD): The ration of lumen output of a lamp at a given operation time as a percentage of 100 hour lumens
Ballast: A device that, by means of resistance, inductance, capacitance or electronic elements, controls the current, voltage and wave form to the required values for proper lamp starting and operation Extinction Voltage: The RMS value of supply voltage at which a freference lamp extinguishes when the supply voltage is slowly reduced from its rated value. The ANSI procedure calls for a 2 to 3% reduction in supply voltage per second Lamp Power Factor: Power consumed by the lamp divided by the product of RMS lamp voltage and RMS lamp current; it is less than unity on magnetic ballasts operating at 50 or 60 hz 
Ballast Characteristic Curve: The curve of lamp wattage vs. lamp voltage over a range of normal lamp voltages when a HID ballast is operated at a given supply voltage Formed Body Arc Tube: Precisely reproducible ellipsoidal arc tube formed by pressurizing molten quartz inside a mold; produces consistent arc tubes with higher efficacy and improved color uniformity  Lamp Voltage: The true RMS voltage of a fully warmed-up lamp 
Ballast Power Factor: Power (watts) consumed by the lamp and ballast divided by the product of line voltage and line current; a measure of power quality and of concern to utilities  HID: High Intensity Discarge lamps; included metal halide (quartz and ceramic), mercury vapor and high pressure sodium (HPS)  Lamp Power: The power consumed by a lamp after warm-up, measured in watts 
BTL: The distance from ballast to lamp  High-Power-Factor (HPF) Ballast: A ballast designed so that the input power factor is not less than 90% when the ballast is operated at the rated supply voltage using an appropriate reference lamp Lamp Regulation: The ratio of changes in lamp power to changes in lamp voltage, often expressed in graphical format 
Burning Position: The position or orientation in which the lamp operates High Reactance Autotransformer (HX) Ballast: An autotransformer lag circuit that uses a magnetic shunt path between primary and secondary coils to control reactance; has operating characteristics similar to those of a reactor and has input taps to accept a wide range of supply voltages  Lead Ballast: A magnetic ballast having a leading lamp current with respect to the supply voltage; current limimiting is accomplished by means of an inductor as well as a capacitor connected in series with the lamp. This includes CWA and CWI ballasts 
Cold Start Time: The amount of time from the application of ballast voltage to ignition of the arc dischare in a cold lamp  Hot Restart or Restrike Time: The time from lamp extinction to lamp re-start after a supply voltage interruption  Light Center Length (LCL): The distance from the center of the visible arc discharge to the bottom contact of the base 
Color Rendering Index (CRI or Ra): A measure of a light source's ability to render colors relative to a standard of 100  Hybrid Ballast: A Venure Lighting lag (magnetic) ballast designed with a low current crest factor for improved lamp performance.  Line Regulation: The ratio of changes in lamp power to changes in ballast input voltage often expressed as a percentage 
Constant Wattage Autotransformer (CWA) Ballast: A magnetic autotransformer lead ballast circuit incorporating a capacitor in series with the lamp. Compared to other ballasts, CWA regulates over a wider input voltage range, holding lamp current nearly constant  Ignitor: An electronic device, which provides, by itself or in combination with other circuit components, the appropriate electrical pulses to start and discharge lamp Lumens (photopic): A measurement of light at daytime levels; takes into account the human eye sensitivity curve so that more weight is given to the yellow-green part of the light spectrum 
Constant Wattage Isolated (CWI) Ballast: A magnetic lead ballast circuit incorporating a fully-isolated secondary winding; it has a capacitor inseries with the lamp and the same performance feature as the CWA ballast  Initial Lumens: The light output of a lamp at related power on a reference ballast after 100 hours of operation Lumen Maintenance: The lumen output of a lamp at a given operating time as a percentage of 100 hour lumens 
Correlated Color Temperature (CCT): The preceived "color" of the light emitted by a lamp expressed in kelvin (K) units  Input Power: See System Power  Lumens Per Watt (LPW): See Efficacy 
Current Crest Factor: The ratio of the peak-to-RMS value of lamp current. Metal Halide magnetic values range from 1.5 to 1.8  Lag Ballast: A magnetic ballast having a lagging lamp current with respect to the supply voltage. Current limiting is primarily inductive; holds lamp power reasonably constant with respect to lamp voltage variations  Maximum Overal Length (MOL): The maximum allowable distance from the top of the glass bulb to the end contact of the base 
Economic Life: The number of hours a group of lamps will burn before it is economically and aesthetically advisable to group relamp (typically 60% to 75% of rated life)