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how light is produced in a fluorescent lamp

elctrons from the cathodes strike the mercury atoms producing uv energy.

The uv energy is converted to visible light by the phospor coating on the inner surface of the lamp glass

how is the color of light output varied in a fluorescent lamp?

by varying composition of the phospor powerder

a starting ballast in a flourescent lamp functions

it performs two functions. It provides the high striking voltage to ignite the tube, and it limits the current in the tube once the tube lights

two advantages of fluorescent over incadescent

higher efficacy (more lumens per watt) and longer life

3 common lamp bases for fluorescent lamps

bipin, single pin, and recessed double-contact

rated life for fluorescent lamps is

7500 to 20,000 hour range

fluorescent lamp service life is reduced by

switching too frequently, operating with the wrong ballast, using excessive voltage, losing cathode pre-heat during start up

fluorescent light seasoning

light output decreases over the first 100 hours. beyond this the decrease is much more gradual, the drop in light is due to phospor deterioration and the tube wall blackening caused by tungsten emission from the cathodes, takes 100 hours to establish a smooth non flickering light

fluorescent ballast hum

ballast hum could be a problem with fluorescent luminaires. ballast are also rated for noise with letter codes. A for quietest, F for loudest

major cause of ballast failure

high ambient temperature, a ten degree rise in ambient temperature above the rated ballast temp can decrease the service life by 50 %

to stop the stroboscopic effect

use lead lag ballasts operating in a twin lamp fixture. these two lamps operate out of phase and reach their max light output at different times. connecting lamps on seperate phases on a 3 phase system also eliminates this problem

what are 3 classifications of fluorescent fixtures?

preheat, instant start, rapid start

what class of luminaire takes the longest to light?

pre heat cct

a pre heat cct includes a

starter and a ballast

an instant start circuit includes

a ballast with an autotransformer, this lamp lights instantly with no cathode pre heating,which is referred to as cold cathode starting

rapid starting circuit

is the most popular type of fixture because it eliminates 3 problems with the instant start: large and heavy ballasts, high striking voltage, reduced lamp life

electronic ballast ELVs

this design replaces the standard core and coil ballasts with solid state circuitry.electronic ballasts take low frequency AC line voltage and convert it to DC voltage

what is the common procedure for troubleshooting a malfunctiong fluorescent fixture?

substitute good parts to see if they fix the problem. Check lamp, ballast, lamp contacts

3 main type of HID lights are

mercury vapour, metal-halide, high pressure sodium

4 common applications in which HID is used

industrial, commercial, sports, and street lighting

inside HID arc tubes

a highly concentrated and intense arc produces radiation with a wavelength within the visible light spectrum

all HID lamps require

ballasts

mercury vapor lamps

vaporizes the mercury gas and permits striking of the main arc. it takes 3-7 minutes to reach full light output

if power outage occurs in a mercury vapor lamp

the arc extinguishes and will not restrike until the lamp cools and pressure is reduced. restrike time takes 4-6 minutes

efficacy of mercury vapor lamps is

30 to 65 lumens / watts range

color rendition index for mercury lamps is

40-50

mercury vapor lamps life

24,000 hours and has the longest rated life in the HID family

metal halide lamps

are similar in construction to mercury vapor. additional compounds of metal and halogen improves the efficacy and color rendition of the lamp

metal halide lamps cri is

70 rating

metal halides startup and restrike time

hgher starting voltage than mercury lamps, start up time is 5-7 minutes, restriking intervals is 15 minutes or longer (longest for HIDs)

metal halides life

15,000 hours

a high pressure sodium lamp has

no starting electrode, special circuitry in the ballast that provides an initial high voltage spike of 2500 volts or more, an arc tube that contains xenon gas and a small amount of sodium amlagam

high pressure sodium restrike time

is usually less than one minute

HPS efficacy

highest of all HIDS, 140 lumens per watt