Specifier Reports Dimming Electronic Ballasts Volume 7 Number 3 October 1999 Program Sponsors Energy Center of Wisconsin Iowa Energy Center Lighting Research Center New York State Energy Research and Development Authority Northwest Energy Efficiency Alliance United States Department of Energy United States Environmental Protection Agency United States General Services Administration Contents Introduction............................................... ..... 1 Ballast Technology......................................... 2 Control Signal Circuitry................................. 3 Control Devices.............................................. 3 Performance Characteristics......................... 4 Alternative Technologies............................... 6 Performance Evaluations............................... 8 Further Information...................................... 12 Data Table Terms and Definitions.............. 13 Data Tables Manufacturer-Supplied Data...................14 NLPIP Evaluations.................................. 22 Manufacturer Contact Information........ 22 High-frequency dimming electronic ballasts designed to operate linear and compact fluorescent lamps Figure 1. Dimming Electronic Ballasts, Control Devices, and Fluorescent Lamps NLPIP Online NLPIP Online is a service of the Lighting Research Center (LRC). The Web site (www.lrc.rpi.edu) contains a full library of NLPIP publications, including Specifier Reports, Lighting Answers, and searchable manufacturers’ data and NLPIP test results. When NLPIP tests new dimming electronic ballasts, the data will be updated online. Introduction Dimming electronic ballasts for fluorescent lamps can save energy and increase the range of illuminances provided by a lighting system. A dimming system saves energy relative to a non-dimming system, assuming lamps are dimmed and both systems are operating for similar periods of time. Most dimming electronic ballasts are silent and cause no perceptible flicker. They represent a significant im- provement over dimming magnetic ballasts, many of which hum and may cause dimmed lamps to flicker. Control devices for dimming electronic ballasts include automatic and manual dimmers, photo- sensors to dim lamps when daylight is available, and energy manage- ment systems that dim lamps during peak demand hours or at night.
Transcript
Specifier ReportsDimming Electronic Ballasts
Volume 7 Number 3 October 1999
Program SponsorsEnergy Center of Wisconsin
Iowa Energy Center
Lighting Research Center
New York State Energy Researchand Development Authority
High-frequency dimming electronic ballasts designed to operate linearand compact fluorescent lamps
Figure 1. Dimming Electronic Ballasts, Control Devices, andFluorescent Lamps
NLPIP Online
NLPIP Online is a service of the Lighting ResearchCenter (LRC). The Web site (www.lrc.rpi.edu)contains a full library of NLPIP publications, includingSpecifier Reports, Lighting Answers, and searchablemanufacturers’ data and NLPIP test results. WhenNLPIP tests new dimming electronic ballasts, thedata will be updated online.
Introduction
Dimming electronic ballasts for fluorescent lamps can save energyand increase the range of illuminances provided by a lighting system.A dimming system saves energy relative to a non-dimming system,assuming lamps are dimmed and both systems are operating forsimilar periods of time. Most dimming electronic ballasts are silentand cause no perceptible flicker. They represent a significant im-provement over dimming magnetic ballasts, many of which hum andmay cause dimmed lamps to flicker. Control devices for dimmingelectronic ballasts include automatic and manual dimmers, photo-sensors to dim lamps when daylight is available, and energy manage-ment systems that dim lamps during peak demand hours or at night.
Dimming electronic ballasts are availablefor linear fluorescent lamps and compactfluorescent lamps (CFLs). All linear lampsused with dimming electronic ballasts musthave the bi-pin bases typical of rapid-startlamps because dimming electronic ballastssupply heating voltage to the lamp elec-trodes during lamp starting and operation.For the same reason, CFLs used withdimming electronic ballasts require a four-pin base.
Lamp manufacturers offer two types ofCFLs: amalgam and non-amalgam. Amal-gam CFLs use a mercury amalgam insteadof liquid mercury, allowing them to achievea relatively constant light output over a widerange of temperatures and in differentoperating positions. However, amalgamCFLs require a longer time to reach fulllight output after they are switched on andhave unpredictable light output underdimmed conditions. The National LightingProduct Information Program (NLPIP)tested both amalgam and non-amalgamCFLs for this report. Table 1 on p. 8 lists thetypes of lamps used in testing.
Dimming electronic ballasts can beespecially cost efficient when combined withcontrols such as photosensors. In order tocalculate life-cycle costs, specifiers mustfirst make application-specific assumptionssuch as how long, how often, and to whatpercent lamps will be dimmed. Using thesevalues, total annual energy use and therespective annual costs can be estimatedand compared to the estimated energy useand costs for a non-dimming system.
In November 1995, NLPIP publishedSpecifier Reports: Dimming ElectronicBallasts, which covered dimming electronicballasts for linear fluorescent lamps. Thisreport supersedes the 1995 publication. Inthis issue of Specifier Reports, NLPIPaddresses the effects of dimming onelectrical and photometric parameters offluorescent lighting systems and providesmanufacturer-supplied information andNLPIP testing data for continuous dimmingelectronic ballasts for 4-foot (ft) [1.2-meter(m)] linear T8 fluorescent lamps andCFQ13, CFQ18, CFQ26, CFM26, CFM32,CFS38, and CFM42 CFLs. This reportspecifically focuses on ballast-lamp interac-tion and presents information specifiersneed to design systems.
Ballast Technology
A ballast for a fluorescent lamp has twoprimary functions: it provides a high initialvoltage to start the lamp, and it regulateslamp current during operation. Magneticballasts typically operate lamps at 60 hertz(Hz). Common electronic ballasts convert60-Hz line voltage to a much higher fre-quency, between 19 and 100 kilohertz(kHz). With the advent of highly efficientelectronic ballasts, the fluorescent lightingindustry is rapidly progressing towardhigh-frequency operation of fluorescentlamps. The primary advantage of high-frequency fluorescent lighting is theimprovement in efficacy relative to lightingsystems with 60-Hz magnetic ballasts. High-frequency operation also reduces thepossibility of perceptible lamp flicker that issometimes associated with low-frequencyballasts because the lamp phosphors arerefreshed more often.
Ballast Types
Ballasts use one of three starting methods,as defined by the American NationalStandards Institute (ANSI). These arepreheat, rapid, or instant. Preheat starting isused primarily by magnetic ballasts forspecialty lamps such as 2-ft (0.6-m) fluores-cent lamps. Rapid-start ballasts supplyelectrode-heating voltage during startingand operation. Instant-start ballasts do notprovide electrode-heating voltage duringstarting or operation. All dimming elec-tronic ballasts identified by NLPIP for thisreport are rapid-start. ANSI does notprovide standards for dimming electronicballasts as of this date.
Rapid-start ballasts provide low voltageof approximately 3.5 volts alternatingcurrent (Vac) to the electrodes, heatingthem to approximately 1800º Fahrenheit (F)[1000º Celsius (C)] in 1 to 2 seconds.Then the ballast applies a starting voltageof 200 to 300 Vac to strike the arc. Rapid-start ballasts start lamps with a brief delay,but without flashing. Recently, a number ofballast manufacturers have introducedballasts that preheat the lamp electrodesbefore applying the starting voltage andcontrol the electrical operation during thestarting period more accurately thantraditional rapid-start ballasts. These
Specifier Reports: Dimming Electronic Ballasts 3
Programmed-Start Ballasts
Similar to rapid-startballasts, programmed-startballasts preheat the lampelectrodes before startingthe lamp. These ballastsprovide very low lampstarting voltage during thepreheat time. This low levelof lamp starting voltagehelps to reduce glow currentand minimize sputteringduring lamp starting to bettermaintain lamp life. After thepreheating period, lampvoltage increases to strikethe lamp arc.
Figure 2. Control Devices
ballasts are generically referred to asprogrammed-start ballasts, but ANSI has notofficially adopted a definition for this term.Manufacturers are also developing otherrapid-start technologies that have namessuch as modified rapid-start and controlledrapid-start.
Rapid-start ballasts dim lamps by reduc-ing the effective lamp current. Electrodevoltage is concurrently increased to main-tain electrode heating. During lamp opera-tion, lamp electrodes should be maintainedat a temperature between 1100 and 1800ºF(600 and 1000ºC) to maximize lamp life. Athigher temperatures the emissive coatingon lamp electrodes evaporates, and at lowertemperatures the electrodes may lose theiremissive coating through sputtering.
Control Signal Circuitry
Dimming electronic ballasts contain one oftwo types of control circuits: low voltage orhigh voltage. The control signal range is therange of the electrical signal (in volts) that acontrol device uses to signal the dimminglevel to a ballast. Each ballast is designedfor a particular control signal range; Tables2 and 3 list ballasts and their associatedcontrol signal ranges.
In addition to their power supply wires,low-voltage dimming electronic ballastshave two wires for a low-voltage controlcircuit, often rated at 0 to 10 volts directcurrent (Vdc). The ballast supplies voltageto a control device, such as a photosensor.For full light output on this circuit, thecontrol device returns the maximum controlsignal to the dimming ballast. For less thanfull light output, the control device reducesthe voltage across the control wires, causingthe ballast to dim the lamps. As the controlvoltage approaches 0 Vdc, the ballast dimsthe lamps to the lowest light output possiblefor that system.
High-voltage dimming electronic ballastsdo not have additional control wires.Instead, high-voltage control devices suchas manual dimmers are typically installedbetween the electrical supply and the “hot”lead of the ballast and can be used toreplace light switches.
Control Devices
Control devices (shown in Figure 2) areavailable for a wide variety of applications.Many dimming control devices can operatemore than one ballast simultaneously.Manual dimmers are designed to replacestandard wall switches. Automatic timersare control devices that can automaticallydim lights at predetermined hours. Auto-mated control devices operate with orwithout regular user control.
Photosensors can be used when day-light is available in a space or for lumenmaintenance control. The photosensordetects the light in a space, then adjuststhe control signal to maintain a relativelyconstant level of light. Occupancy sensorsare sometimes used to provide automatictwo-level control: maximum light outputwhen they detect motion and reducedlight output when they detect no motion.(See Specifier Reports: Photosensors, 1998;Occupancy Sensors, 1997).
NLPIP recommends that specifiersselect dimming electronic ballasts andcontrol devices that are either made by thesame manufacturer or listed in manufactur-ers’ literature as being compatible. Controlsignal range is key to ballast/control devicecompatibility and is often reported inmanufacturer information. Always specify acontrol device with a control signal range asclose as possible to that of the ballast. Adevice with a wider control signal range is abetter selection than one with a controlsignal range that does not completelyencompass the ballast’s effective dimmingcontrol range. If the control device’s signalrange is too great, however, much of itsrange may produce no response from theballast and precise control of light outputmay be more difficult. If the control signalrange is less than a ballast’s effectivedimming control range, the ballast’s fulldimming range will not be usable.
PerformanceCharacteristics
Dimming Operation
Dimming can be described in terms ofpercentage of maximum light output,measured illuminance, and perceivedbrightness. Perceived brightness accounts
for the adaptability of the human eye whenexposed to different amounts of light. Forexample, a space with the system dimmedto 25% of maximum light output may beperceived as being almost half as bright asthe same space with the system at maxi-mum light output. Figure 3 illustrates thetheoretical relationship between measuredilluminance and perceived brightness.
NLPIP observed some variations indimming operation during the testing ofdimming electronic ballast systems. Alldimmers were supplied by the ballastmanufacturers. The manufacturers’ infor-mation for all of the ballasts tested indicatesthat each product provides continuousdimming. NLPIP researchers observed“step” dimming characteristics for somesystems, in which the light output changedin discrete (and noticeable) steps ratherthan continuously.
Also, the mechanical range of the slidedimmers used by NLPIP in testing some-times did not exactly coincide with thedimming range of the lamps and ballasts.The lamps in some cases extinguishedbefore the slide dimmer was at its lowestsetting. NLPIP recommends that specifiersobtain samples of the lamps, ballasts, andcontrol devices being considered. Thesesamples should be evaluated in a mock-upbefore the system is specified and installed.
Certifications
CBM SealThe Certified Ballast Manu-facturers (CBM) consists ofmanufacturers of fluorescentlamp ballasts who participatein a certification program thatrequires independent labora-tory examination and certifi-cation. To bear a CBM seal,a ballast must meet ANSIspecifications.
ULUnderwriters Laboratories(UL) sets safety standards forbuilding materials, electricalappliances, and other prod-ucts. To be UL listed, theballast must meet all ULsafety requirements.
CSAThe CSA mark means thatthe ballast is certified for theCanadian market, followingthe applicable Canadianstandards.
C-ULThe C-UL listing mark isapplied to products for theCanadian market. Productswith this mark have beenevaluated and found toconform to Canadian safetyrequirements for theCanadian market.
(Adapted from the Lighting Handbook, 8th edition)
10 20 30 40 50 60 70 80 900 100
Perceived Brightness (%)
100
90
80
70
60
50
40
30
20
10
0
Mea
sure
d Ill
umin
ance
(%)
25
5
22.4 77.5
Specifier Reports: Dimming Electronic Ballasts 5
Dimming Range
The dimming range of a lighting systemvaries with different dimming ballasts.NLPIP found that a few of the dimmingballasts tested could dim lamps to less than5% of maximum light output and that mostcould dim lamps to less than 20% of maxi-mum light output. The dimming rangerequired for a specific installation dependson the application. A ballast that dims to 20%of maximum light output is adequate formany photosensor applications. Ballastswith a broader dimming range may bepreferable for applications where dimming isneeded to accommodate audiovisual needsor to create architectural effects.
Power Quality
Dimming devices can, in some instances,affect power quality. Power quality describesthe extent to which a specific electronicdevice distorts the voltage or currentwaveform and/or changes the phase rela-tionship between them. A device with idealpower quality characteristics neither distortsthe supply voltage nor affects the voltage-current phase relationship. NLPIP evaluatedpower quality for dimming electronic ballastsby measuring power factor and current totalharmonic distortion (THD).
Power factor is defined as the ratio ofactive power [in watts (W)] to apparentpower [in volt-amperes (VA)]. Apparentpower is the product of root-mean-square(rms) voltage and rms current. Power factorranges from 0 to 1. A power factor of 1 meansthat the current voltage waveforms are inphase and neither waveform is distorted. Inother words, when power factor is 1, apparentpower and active power are equal.
Any distortion of the current wave shapecauses distorted current to flow through theelectrical distribution system, thus reducingpower factor. These distortions are expressedby current THD. Distorted currents may haveother effects, including interference with theoperation of electronic equipment, bothnearby and remote. High current THDlevels can cause overheating in conductorsand transformers. For more information,see Lighting Answers: ElectromagneticInterference Involving Fluorescent LightingSystems, 1995, and Lighting Answers: PowerQuality, 1995.
Ballast Life
Ballast life is listed in Tables 2 and 3, andranges from 10 to 20 years. Ballast lifedepends upon maximum ballast casetemperature and operating voltage. Hightemperatures or high peak voltage candamage electronic components or shortentheir lives. Tables 2 and 3 list maximumrated ballast case temperatures for alldimming electronic ballasts supplied bymanufacturers. These range from 104 to185ºF (40 to 85ºC). If ballasts are operatedat temperatures higher than those recom-mended, warranties could become void.NLPIP did not test ballast case temperatures.
I22 + I3
2 + I42 + ...
I12
Definition and Standards for Harmonic Distortion
Current THD is a measure of the amount of distortion in a current’s waveshape: the higher the THD value, the greater the distortion. American Na-tional Standards Institute (ANSI) Standard C82.11 sets a limit of 32% currentharmonic factor for electronic ballast systems. The United States Departmentof Energy has proposed limiting current THD to 20% on all lighting equip-ment. Many utilities only include ballasts that have THD less than 20% in theirenergy-efficiency programs.
Harmonics that are odd triple multiples of the fundamental frequency (3rd,9th, 15th, ...) have the greatest potential impact on electrical systems be-cause the current from these harmonics flows on the neutral conductor andmay overload it. ANSI C82.11 also sets limits for odd triple multiples andother harmonics.
In this report, NLPIP uses the definition of the Institute of Electrical andElectronic Engineers (IEEE 519–1992) because that is how ballast manufac-turers typically report it. This definition coincides with the definition of har-monic factor used by ANSI, Canadian Standards Association (CSA) and theInternational Electrotechnical Commission (IEC).
THD =
whereI1 = fundamental current,I2 = current in second harmonic,I3 = current in third harmonic,I4 = current in fourth harmonic,etc.
× 100
his d
ANSI, CSA, and IEC define THD as the ratio of the harmonic content to therms value of the periodic current (all of the harmonic components includingthe fundamental), which is expressed as
THD = × 100I2
2 + I32 + I4
2 + ...
I12 +I2
2 + I32 + I4
2 + ...
6 Specifier Reports: Dimming Electronic Ballasts
Lamp Starting
Rapid-start ballasts (including dimmingelectronic ballasts) can reduce lamp life ifthey do not heat the electrodes enoughbefore starting the lamp. Because electrodetemperature cannot be measured directly,the lighting industry uses two relatedmetrics: electrode preheat time andelectrode-heating voltage. ANSI specifies aminimum preheat time of 0.5 seconds (s)for rapid-start ballasts and an electrode-heating voltage of 2.5 to 4.4 Vac for non-dimming ballasts operating F32T8 lamps.All dimming electronic ballasts tested byNLPIP preheated lamp electrodes for atleast 0.5 s. NLPIP found that at maximumlight output, most dimming electronicballasts provided electrode-heating voltagewithin the range specified by ANSI.
When lamps are dimmed, the electronflow in the arc decreases. To compensatefor this decrease, most ballasts tested byNLPIP exceeded 4.4 Vac of electrode-heating voltage when operating at theminimum light output setting.
In addition to electrode-heating voltageand preheat time, NLPIP has foundevidence to support the use of anothermetric to predict lamp and ballast compat-ibility for rapid-start electronic ballasts(Davis and Ji 1998). RH/RC is the ratio ofhot electrode resistance to cold electroderesistance for each lamp-ballast system as away to estimate electrode temperature justbefore a lamp is started (Hammer 1995). AnRH/RC value of 4.25 equates to a lampelectrode temperature of 1300ºF (700ºC),which lamp experts consider the minimumtemperature for proper lamp starting. ANSIis currently considering RH/RC as a newmetric for determining whether rapid-startlamp-ballast systems adequately heat lampelectrodes before starting. To find out moreabout RH/RC, see the sidebar on the facingpage or NLPIP’s Guide to Selecting Fre-quently Switched T8 Fluorescent Lamp-Ballast Systems, 1998.
PLC Transmitters andElectronic Ballasts
Interference from high-frequency electronic ballastsmay disrupt some power-linecarrier (PLC) signals. PLCsare systems that transmithigh frequency (50 to 500kHz) signals via the powerlines of a building. Thesesignals control devices suchas synchronized clocks orcontain voice transmissionssuch as intercom messages.Some commercial andresidential energy manage-ment systems also usePLCs. Specifiers shouldconsult the manufacturers ofboth the PLC device and theelectronic ballast to ensurecompatibility.
Lamp Operation
Ballast factor (BF) is the ratio of the lightoutput of a lamp or lamps operated by aspecific ballast to the light output of thesame lamp(s) operated by a referenceballast. Most electronic ballasts have BFsless than 1.0, although some electronicballasts have BFs greater than 1.0 toprovide high light output. An electronicballast with a BF of 1.0 requires less powerthan a reference ballast, even though theyboth produce the same light output.
Lamp current crest factor (CCF) is theratio of peak lamp current to rms lampcurrent and so is a measure of current waveshape. A high lamp CCF indicates highpeaks in the current wave shape that canreduce lamp life. CCF is determined by theballast. The CCF for a sine wave is 1.41.ANSI specifies CCF less than 1.7 to ensurerated lamp life (ANSI 1993).
Alternative Technologies
Lighting Circuit Power Reducers
Lighting circuit power reducers are retrofitdevices designed to reduce the energy useof a lighting circuit. These power reducersare installed at electrical panels between acircuit breaker and the lighting load toreduce the active power of the entirelighting circuit. The end result is lesspower, less illuminance for the space, andin some instances, reduced system efficacy.Specifiers considering this type of retrofitfor existing lighting applications should seeSpecifier Reports: Lighting Circuit PowerReducers, 1998.
Step-Dimming
Another alternative to a continuouslydimming electronic ballast is a step-dimmingelectronic ballast with a built-in switch forselecting preset dim settings. The ballastmust be physically accessed to change thesettings, so it cannot be remotely controlled.Many controls can be used to step-dimballasts in a two-level mode (either maxi-mum or reduced light output).
Specifier Reports: Dimming Electronic Ballasts 7
Fluorescent System Reliability
The rated life of a fluorescent lamp is thenumber of hours at which half the lamps ina large test group have failed (IESNA1987). Lamp life testing is performed in acontrolled open-air environment. The lampsare cycled continuously on for three hoursand off for twenty minutes. This is knownas the standard cycling rate. Previous re-search (Vorlander and Raddin 1950) hasshown that starting a lamp more frequentlydecreases lamp life, while starting it lessfrequently increases lamp life.
A T8 linear fluorescent lamp typically has arated life of 20,000 hours. Using the stan-dard cycling rate, it would take three to fouryears to test these lamps. As a result,when new lamps or ballasts are developed,there is a long delay before a determinationcan be made about the longevity of a fluo-rescent system. For this reason, there isinterest in developing a life-predicting tech-nique. The technique could be used to testlamp and ballast combinations and deter-mine their compatibility.
One technique that has been used withrapid-start fluorescent systems for the pastten years or more is RH/RC. RH/RC is theratio of the hot electrode resistance to thecold (or ambient) electrode resistance. Theratio is part of an equation that allows theresearcher or designer to predict the tem-perature of the electrode during starting justbefore the lamp arc is established. Beforestarting the lamp, the ballast should heatthe electrodes to at least 1300ºF (700ºC),which equates to an RH/RC value of 4.25. Ifthe electrodes are not heated enough,sputtering will occur, but if they are over-
heated, too much of the emissive coatingmay evaporate. The relationship betweenRH/RC and electrode overheating is notknown at this time.
Cold electrode resistance can be measuredusing an ohmmeter capable of measuringlow resistances, such as a few ohms. Hotelectrode resistance cannot be measureddirectly. It must be calculated by measuringthe voltage applied to the electrode and theelectrode current during starting. It is criticalto make these measurements just beforethe lamp arc is established. Several meth-ods of measuring this hot electrode resis-tance have been presented, most of whichare similar in technique.
For this testing, NLPIP used a measure-ment technique similar to Mortimer (1996).The RC was measured at a room temperatureof 77±2ºF (25±1ºC). For the RH measure-ment, the electrode-heating voltage andelectrode-heating current values were mea-sured immediately before the lamp’s transi-tion from glow to arc. NLPIP calculated theRH value and the RH/RC ratio based onthese values.
NLPIP measured RH/RC for two differentballasts that were tested in this report. Oneballast operated two 26-W CFLs and theother ballast operated one 32-W CFL. Foreach ballast, nine lamps (three from eachof three different lamp manufacturers) weretested. This test demonstrates that RH/RCis dependent on which lamp is used with aparticular ballast. However, the data sug-gest that the differences between ballastsare greater than the differences betweenlamps. The results are shown in the follow-ing table.
tsallaB pmaL RnaeM H R/ C egnaR noitaiveDdradnatS
L nortuE-2-021-62FC-BDF
)gnithgiLEG(W-62 80.4 02.1 423.0
)AINAVLYSMARSO(W-62 44.4 16.0 771.0
)gnithgiLspilihP(W-62 46.3 04.1 753.0
spmaLW-62llAroFegarevA 50.4
erP etilocsD-SR31T-VUP
)gnithgiLEG(W-23 44.5 66.0 072.0
)AINAVLYSMARSO(W-23 55.4 70.0 030.0
)gnithgiLspilihP(W-23 39.5 88.0 153.0
spmaLW-23llAroFegarevA 03.5
Specifier Reports: Dimming Electronic Ballasts 7
8 Specifier Reports: Dimming Electronic Ballasts
Table 1. Lamps and Luminaires Used in NLPIP Testing
NA = not applicable
Switch-Dimming
A third alternative, useful for new construc-tion applications or for extensive lightingrenovations, is to wire lamps within lumi-naires to different control circuits. Forexample, two of the lamps in a three-lampluminaire can be wired to a control circuitseparate from the third lamp. Depending onwhich circuits are switched on, one, two, orall three lamps can be operated.
Performance Evaluations
NLPIP tested 120-Vac ballasts for two 32-WT8 lamps (F32T8), two 18-W quad tubelamps (CFQ18), two 26-W quad tube lamps(CFQ26), and one 32-W triple tube lamp(CFM32). NLPIP conducted all testing atthe LRC’s laboratory in Watervliet, NewYork, from March to June 1997 and fromApril to July 1999.
Table 1 contains product informationfor lamps and luminaires used in NLPIP’stesting. Tables 2 and 3 contain manufacturer-supplied product information for dimmingelectronic ballasts for linear fluorescent andcompact fluorescent lamps, respectively.Table 4 contains the results of NLPIP’stesting. Table 5 contains a list of manufactur-ers along with contact information.
NLPIP Testing Procedure for DimmingBallasts for T8 Lamps
NLPIP requested three samples of dimmingelectronic ballasts for two F32T8 lamps andone dimmer from each manufacturer. Thedimmers used were not necessarily manu-factured by the ballast manufacturers but
were supplied to NLPIP by them. Whenpossible, NLPIP purchased an additionalballast from a local vendor for each manufac-turer. One randomly selected ballast fromeach set was tested with the manufacturer-supplied dimmer. NLPIP used lamps froma single manufacturer (listed in Table 1) totest all the ballasts for a particular lamp type.All lamps were seasoned for at least 100hours (h) and then operated for at least15 h immediately before the first measure-ments. Ambient temperature was main-tained at 77±2ºF (25±1ºC) and input voltageat 120±0.12 Vac.
Figure 4 illustrates the apparatus fortesting dimming ballasts for T8 lamps.NLPIP used a partitioned lamp rack toperform simultaneous electrical and lightoutput measurements. Each lamp compart-ment was painted black inside and designedto hold one 4-ft (1.2-m) lamp and oneilluminance detector so that the light outputfrom each lamp could be measured inde-pendently. The illuminances from bothdetectors were added to give the total lightoutput for the system.
NLPIP first took electrical and illumi-nance measurements at the maximum lightoutput setting of the supplied dimmer foreach ballast tested. Then the system wasmanually dimmed to 80% (±3%) of themaximum illuminance. The same set ofmeasurements was taken after the lightoutput stabilized. NLPIP continuouslymonitored light output and considered itstabilized when the variation over a five-minute period was less than 2%. Thisprocedure required at least 30 minutes foreach measurement. The procedure wasrepeated with the following light output
81QFC gnithgiLEG P4/72XPS/XBD81F N reilothgiL 021F8127 WLC6508
62QFCMARSO
AINAVLYS728/E/DD62FC N reilothgiL 021F6227 WLC6508
23MFC gnithgiLspilihP P4/03/W23T-LP Y reilothgiL 021E2317 WLC0508
Specifier Reports: Dimming Electronic Ballasts 9
Dimensions: 48 in. (L) × 18 in. (W) × 101/2 in. (H)Each lamp compartment was 9 in. wide1 cm = 0.394 in.
Figure 4. Testing Apparatus for Linear T8Fluorescent Lamps
levels (±3%) in order: 60%, 40%, 20%, theminimum level (if lower than 20%) achiev-able with the supplied dimmer, 20%, 40%,60%, 80%, and finally, the maximum lightoutput level. The values were the samewhen lamps were measured from minimumto maximum light output and from maxi-mum to minimum light output.
Dimming range, which had an upperlimit of 100%, was calculated for eachindividual ballast. Each ballast’s minimumdimmed level is reported as a percentage ofits maximum light output in Table 4.
Results
Table 4 contains data obtained at maximumlight output, minimum light output, and 40%of maximum light output. The 40% level waschosen to provide a benchmark to comparedimmed performance. This is the lowestdimmed level that all ballasts met.
Relative Light Output
To calculate maximum relative light output(RLO), NLPIP normalized the data for allthe F32T8 systems to the highest maximumlight output measured. This value wasassigned an RLO of 100%, and the otherdata were scaled accordingly. For example,in Table 4, within the F32T8 lamp group,the system using the Philips Lightingballast with catalog number ECD-120-2/32Thad the highest light output, so its RLO was100%. The light output from the othersystems for F32T8 lamps were normalizedto this RLO.
RLO correlates with ballast factorbecause they are both based on lightoutput. For example, the NLPIP-measureddata in Table 4 for two F32T8 120-Vac lampsshows that RLO ranged from 100 to 72%.This range correlates with manufacturer-supplied information in Table 2 for the samelamp types, for which ballast factor rangedfrom 1.00 to 0.74.
Relative System Efficacy
The efficacy of a lighting system is the ratioof the light output to the active power,calculated in lumens per watt (LPW). Forfluorescent lighting systems, systemefficacy can range from approximately 60 to100 LPW. System efficacy depends on thecharacteristics of individual systems andtherefore varies with each application.
Researchers computed relative systemefficacy as the ratio of RLO to system activepower. Researchers then normalized theserelative system efficacy data to the highestvalue at the maximum light output level,which was assigned a relative systemefficacy value of 100%. Figure 5 on p. 10illustrates the overlapping range of RLOs asthe ballasts dim the lamps. These testresults were similar for all the ballasts.
Lamp(OSRAM SYLVANIA F32T8/741)
PartitionIlluminancedetectorholder
Black surface
10 Specifier Reports: Dimming Electronic Ballasts
Figure 5. Range of RLO Compared to Active PowerDimming Electronic Ballasts for Two F32T8 Lamps
NLPIP Testing Procedure for DimmingElectronic Ballasts for CFLs
For commercial applications, dimmingsystems for CFLs are usually sold as apackage including the lamp, ballast,luminaire, and control. For testing pur-poses, NLPIP researchers selected com-mon downlights for two CFQ18 lamps, twoCFQ26 lamps, and one CFM32 lamp.Researchers asked each manufacturer tosubmit two ballast samples and one dim-mer. NLPIP purchased one additionalballast for each manufacturer from anelectrical distributor when possible.
Because of maximum lead lengthconstraints (see the sidebar “Constraints onLength of Ballast Leads for CFL Products”),researchers tested the compact fluorescentlamps and dimming ballasts installed in arecessed downlight in a test chamber.Figure 6 shows the simulated ceilingchamber used by NLPIP for testing CFLs.
During testing, NLPIP researchers heldthe relative positions of the downlight,lamp or lamps, and five illuminancedetectors constant. Researchers used theilluminance measurement at the centerilluminance detector (see Figure 6) tocalculate the RLO for the lamp-ballast
system being tested. Measurements fromthe other illuminance detectors weremonitored to ensure that the luminairelocation and the light distribution re-mained constant. All lamps were seasonedfor at least 100 h and then operated for atleast 15 h, except for the 32-W amalgamlamp, which was operated for more than100 h before the first measurements weremade. Ambient temperature was main-tained at 77±2ºF (25±1ºC), and inputvoltage at 120±0.12 Vac.
For each ballast tested that operatednon-amalgam lamps, NLPIP researchersfollowed the same procedure for electricaland light output measurements as thosedescribed for the ballasts for T8 lamps.For each ballast tested with the amalgam32-W CFM lamp, researchers initially usedthe same testing procedure, but the resultswere non-repeatable for the middle dimmedlevels. Therefore, researchers decided toperform measurements only at the maxi-mum and minimum light outputs achievablewith the supplied dimmers.
For CFL dimming electronic ballasts,researchers calculated RLO and relativesystem efficacy using the method describedin testing procedures for T8 lamp ballasts.
Constraints on Length ofBallast Leads for CFLProducts
NLPIP originally planned totest the CFL ballasts with thelamps inside an integratingsphere. However, some CFLballast manufacturers printlead length constraints ontheir ballast labels. In thecourse of discussions withmanufacturers, NLPIPlearned that the lead lengthrequired between the lamp(s)and the ballast is usually lessthan or equal to 3 ft (0.9 m)and that the proper lengthleads are usually sent to thecustomers with the ballasts.According to the manufactur-ers, longer or shorter leadsalter the lamp signal becauseof varying capacitance, af-fecting the dimming andstarting capability of the lamp.
To evaluate this effect,NLPIP conducted a pilotstudy with one of the two-lamp dimming electronicballasts for CFLs. Resultsshowed that when the leadswere 3 ft (0.9 m) long, thedimming range was asclaimed by the manufacturer(5 to 100% light output).When the leads were 20 ft(6.2 m) long, the lampsextinguished at about 20%light output. At this length,the light output changedconsiderably when research-ers simply moved the wiresrelative to each other. Thislead length constraint madethe sphere testing planimpractical and led toNLPIP’s decision to test thelamps and ballasts within aluminaire.
0
20
40
60
80
100
7065605550454035302520150
Active Power (W)
Rel
ativ
e Li
ght O
utpu
t (%
)
5 10
Specifier Reports: Dimming Electronic Ballasts 11
Figure 6. Simulated Ceiling Chamber Used by NLPIP forTesting CFLs
Figure 7. RLO as a Function of Active PowerDimming Electronic Ballasts for Two CFQ18 Lamps
Figure 8. RLO as a Function of Active PowerDimming Electronic Ballasts for Two CFQ26 Lamps
Results
Minimum Dimmed Level
In one case (Energy Savings ballast ES-1-CFH-42-120-G-DIM-E), the lamps extin-guished before reaching the reportedminimum light output level. In another case(Lutron Electronics ballast FDB-CF26-120-2-E), the lamps flickered at the minimumlevel. For these products, NLPIP reportsthe measured data at the minimum levelachievable without flicker during testing.
Relative System Efficacy
As reported in Table 4 and shown in Figures7 and 8, the CFL ballasts tested by NLPIPdiffered from each other in relative systemefficacy. Figure 8 shows the relationshipbetween RLO and active power for theballasts operating two CFQ26 lamps. Thisfigure illustrates that for the same power,the products tested varied in the light outputthey produced, resulting in different relativesystem efficacies. The difference is greaterat higher active powers.
As shown in Table 4, dimming electronicballasts for CFLs tested at maximum lightoutput showed relative system efficaciesthat ranged from 71 to 100%. Those testedat 40% of maximum showed relative systemefficacies that ranged from 70% to 86%.Those tested at minimum light outputshowed relative system efficacies thatranged from 8 to 62%.
THD and Power Factor
NLPIP found that the THD produced by afew dimming ballasts increased significantlyat dimmed levels. This increase in THDproduced a corresponding decrease inpower factor. Power factor during dimmingranged from greater than 0.99 at maximumlight output to 0.29 at minimum lightoutput. Because THD is expressed as apercentage of the fundamental current, ahigh THD at low light output levels (andlow fundamental current levels) may not bea concern, as the actual distorted current issmall. Current THD ranged from 6 to 18% atmaximum light output, from 5 to 69% at 40%of maximum, and from 7 to 158% at mini-mum light output.
Chamber dimensions: 8 ft (L) × 4 ft (W) × 4 ft (H) and 33 in. above floor
1 cm = 0.394 in. = 0.0328 ft
1 Chamber lid2 Black interior3 Downlight4 Black felt5 Illuminance detectors6 Floor7 Ballast
6
4
1
32
33˝
5
7
0
20
40
60
80
100
Active Power (W)
Rel
ativ
e Li
ght O
utpu
t (%
)
454035302520151050
Lightolier GLT2-18T4-120I
Lutron FDB-CF18-120-2-BPrescolite PUV-21RS-D
Rel
ativ
e Li
ght O
utpu
t (%
)
Active Power (W)
0
20
40
60
80
100
60554540302520151050 35 50
Lutron FDB-CF26-120-2-E
Advance REZ-2Q26
Lightolier GLT2-26T4-120I
Prescolite PUV-22RS-D
120
12 Specifier Reports: Dimming Electronic Ballasts
Further Information
Abesamis, R.S., P. Black, and J. Kessel.1990. Field experience with high-frequencyballasts. IEEE Transactions on IndustryApplications 26(5):810–811.
American National Standards Institute.1997. Lamp ballast – Line frequency fluores-cent lamp ballast, ANSI C82.1-1997. NewYork, NY: ANSI.
———. 1995. Fluorescent lamp ballasts:Methods of measurement, ANSI C82.2-1984R1995. New York, NY: ANSI.
———. 1993. High-frequency lamp ballasts,ANSI C82.11-1993. New York, NY: ANSI.
Audin, L. 1993. All About Ballasts. Architec-tural Record (Lighting Supplement)181(2):13.
Berutti, A., and R.M. Waggoner, eds. 1996.Practical guide to power quality for sensitiveelectronic equipment, 4th edition. OverlandPark, KS: Intertec Electrical Group.
Buddenberg, A., and R. Wolsey. 1995.Compatibility test of dimming electronicballasts used in daylighting and environ-ment controls. In Illuminating EngineeringSociety of North America Annual Conference:Proceedings, New York, NY, July 30–August2, 1995. New York, NY: IESNA. pp. 1–9.
Canadian Standards Association. 1999.Canadian electrical code - Part 1: Safety forelectrical installations, CSA-C22.1-1999.Toronto, Ontario: Canadian ElectricalAssociation.
Davis, R.G. and Y. Ji. 1998. Fluorescent lamp-ballast systems. Prepared for Empire StateElectric Energy Research Corporation.Troy, NY: Lighting Research Center,Rensselaer Polytechnic Institute.
Electric Power Research Institute, CaliforniaEnergy Commission, and U.S. Departmentof Energy. 1993. Advanced lighting guide-lines: 1993, EPRI TR-101022, R1. Palo Alto,CA: EPRI.
Hammer, E.E. 1995. Cathode fall voltagerelationship with fluorescent lamps. Journalof the Illuminating Engineering Society24(1):116–122.
Illuminating Engineering Society of NorthAmerica. 1993. Lighting handbook: Reference& application, 8th ed. Edited by M.S. Rea.New York, NY: IESNA.
Illuminating Engineering Society TestingProcedures Committee. Subcommittee onPhotometry of Light Sources. 1987. IESapproved method for life performance testingof fluorescent lamps, IES LM-40-1987. NewYork, NY: Illuminating Engineering Society.
Institute of Electrical and ElectronicsEngineers. 1992. Recommended practicesand requirements for harmonic control inelectric power systems, IEEE 519-1992.Piscataway, NJ: IEEE.
Ji, Y., and R.G. Davis. 1994. Fluorescentlamp/ballast compatibility. Troy, NY:Lighting Research Center, RensselaerPolytechnic Institute.
Key, T.S. 1979. Diagnosing power quality-related computer problems. IEEE Transac-tions on Industry ApplicationsIA-15(4):381–393.
Mortimer, G.W. Real-time measurement ofdynamic filament resistance. In IlluminatingEngineering Society of North AmericaAnnual Conference: Proceedings, Cleveland,OH, August 5–7, 1996. New York, NY:IESNA. pp. 419–430.
National Fire Protection Association. 1999.1999 National electrical code, NFPA 70.Quincy, MA: NFPA.
———. 1999. 1999 National electrical codehandbook. Quincy, MA: NFPA.
U.S. Bureau of the Census. 1999. Currentindustrial reports: Fluorescent lamp ballastssummary 1998, Q36C(98). Available atwww.census.gov/ftp/pub/industry/1/mq36c985.pdf. Accessed 9/9/99.
U.S. Congress. 1992. Energy policy act of1992. Public Law 102-486. 102nd Cong. 24October 1992.
———. 1988. An act to amend the energypolicy and conservation act to provide forfederal energy conservation standards forfluorescent lamp ballasts. Public Law100-357. 100th Cong. 28 June 1988.
U.S. Environmental Protection Agency,Green Lights Program. 1998. Lightingupgrade manual: Lighting waste disposal.Available at www.epa.gov/buildings/esbhome/tools/wastedi.pdf.Accessed 9/9/99.
Specifier Reports: Dimming Electronic Ballasts 13
U.S. Federal Communications Commission.[Latest issue]. Industrial, scientific, andmedical equipment, 47 CFR 18.
Verderber, R.R., O. Morse, and F.Rubinstein. 1985. Effect of filament powerremoval on a fluorescent lamp system. 1985Industry Applications Society AnnualMeeting, Toronto, Canada, October 6–11,1985. New York, NY: IEEE. pp. xxii, 1786.
Vorlander, F.J., and E.H. Raddin. 1950. Theeffect of operating cycles on fluorescentlamp performance. Illuminating Engineering40(1): 21–27.
Data Table Terms andDefinitions
The following data tables present productinformation supplied by NLPIP and bymanufacturers. The column headings aredefined in this section.
Note that for many of the columnheadings in Tables 2, 3, and 4, there are twosub-headings: Max and Min. The Maxcolumn contains data obtained at eachdimmer’s maximum light output setting.The Min column contains data obtained ateach dimmer’s minimum setting. Table 4also contains data obtained at 40% of eachdimmer’s maximum setting.
Active power. The input power (in watts)for a lamp and ballast combination.
BEF (Ballast efficacy factor). The ratio ofthe ballast factor (as a percentage) to theactive power (in watts). For eample, if theballast factor of a ballast is 0.88 and itsactive power is 33W, the ballast’s BEF is88433 5 2.67%/W.
BF (Ballast factor). The ratio of the lightoutput of a fluorescent lamp operated by aparticular ballast to the light output of thesame lamp operated by a reference ballastunder standard testing conditions, given asa percentage.
CCF (Current crest factor). The peaklamp current divided by the root-mean-square (rms) lamp current. CCF rangesfrom 1.0 to infinity. ANSI requires CCF to beless than 1.7; lamp manufacturers usuallywill not warranty their lamps if operated onballasts with CCFs greater than 1.7.
Control signal range. The range of theelectrical signal (in volts) that a control
device uses to signal the dimming level toa ballast.
Current THD. A measure of the degree towhich the current waveform deviates fromsinusoidal, expressed as a percentage.
Glow current. The current that flows fromthe lamp electrodes during the electrodepreheat period while the lamp startingvoltage is applied.
Lamp current. The current flowingbetween the lamp electrodes duringoperation.
Low-voltage circuit protection. Protec-tion for the ballast’s low-voltage controlcircuit from high voltage spikes. Does notapply to high-voltage controls.
Maximum ballast case temperature.The maximum temperature of the ballastcase for which the manufacturer’s life ratingis valid.
Maximum relative light output. Theilluminance measured at a fixed distancefrom the lamps. For each lamp type, themaximum relative light output was normal-ized to the highest value at the maximumlight output level, which was assigned avalue of 100%.
Minimum dimmed level. The lowestdimmed level achieved by the ballast,expressed as a percentage of that ballast’smaximum light output.
Minimum starting temperature. Theminimum ambient temperature at which theballast will reliably start fluorescent lamps.
Operating electrode voltage. The voltagethat the ballast supplies to the lamp elec-trodes while the lamp is operating.
Power factor. The ratio of active power(in watts) to apparent power (in rms volt-amperes).
Relative system efficacy. The ratio ofrelative light output (RLO) to system activepower. For each lamp type, relative systemefficacy was normalized to the highest valueat the maximum light output level, whichwas assigned a relative system efficacyvalue of 100%.
Starting method. All the dimming elec-tronic ballasts in this report use one ofthese starting methods: rapid-start (RS),programmed-start (PS), or controlled rapid-start (CRS).
14 Specifier Reports: Dimming Electronic Ballasts
Table 2. Manufacturer-Supplied Data: Dimming Electronic Ballasts for Linear Fluorescent Lamps
NA = not applicableNS = not supplied°C = 5/9 (°F-32)1 kg = 2.2 lba Catalog numbers in red indicate products tested by NLPIP.b Manufacturer claims that power factor at minimum light output, current THD at minimum light output, and control signal range do not depend
on the ballast alone; they also depend on the control device used.c Operated with the dimming module MP3 (allows dimming to 10%).d Prices are retail for small quantity orders.
XkraM 23S3-ZEV 89.0> AN b 01< AN b 401 02 SP 0.2 – 0.4 0.4 – 8.4
gnithgiLspilihP nortocE T23/3-772-DCE 89.0> AN b 01< AN b 401 02 SP 4.4< 6.3>
NA = not applicableNS = not supplied°C = 5/9 (°F-32)1 kg = 2.2 lba Catalog numbers in red indicate products tested by NLPIP.b Manufacturer claims that power factor at minimum light output, current THD at minimum light output, and control signal range do not depend
on the ballast alone; they also depend on the control device used.c Operated with the dimming module MP3 (allows dimming to 10%).d Prices are retail for small quantity orders.
Specifier Reports: Dimming Electronic Ballasts 17
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on the ballast alone; they also depend on the control device used.c Data were not supplied for this product because the company is no longer in operation.
Specifier Reports: Dimming Electronic Ballasts 19
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NA = not applicableNS = not supplied°C = 5/9 (°F-32)1 kg = 2.2 lba Catalog numbers in red indicate products tested by NLPIP.b Manufacturer claims that power factor at minimum light output, current THD at minimum light output, and control signal range do not depend
on the ballast alone; they also depend on the control device used.c Data were not supplied for this product because the company is no longer in operation.
Specifier Reports: Dimming Electronic Ballasts 21
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352 61 0 6.1< 6.1< 04 – 021 AN SN SN 01 51 041 3 ASC/LU 0 03< 93.0
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22 Specifier Reports: Dimming Electronic Ballasts
Table 4. NLPIP-Measured Data: Dimming Electronic Ballasts for Compact and Linear Fluorescent Lamps
NT = not tested due to unstable light output with amalgam lamps.a Manufacturer-supplied data were not supplied for this product because the company is no longer in operation.
Principal Investigator: Conan O’RourkeTechnical Writer: Julie HarrellTechnical Editor: Alma TaylorProgram Director: Rick CobelloProduction Managers: James Gross,
Susan MaharGraphics and Photography: James Gross,
Susan Mahar
The following people provided technicalreview: P. Banwell, U.S. EnvironmentalProtection Agency; F. Barwig, Iowa EnergyCenter; R. Davis, University of Colorado;D. Grant, Lighting Design Lab; N. Olson,Iowa Energy Center; S. Pigg, Energy Centerof Wisconsin; W. VonNeida, U.S. Environ-mental Protection Agency; and M. Walton,New York State Energy Research andDevelopment Authority. Reviewers are listedto acknowledge their contributions to thefinal publication. Their approval or endorse-ment of this report is not necessarily implied.
Production of this report involvedimportant contributions from manystaff members at the LRC: S. Hayes,K. Heslin, H. Huang, R. Leslie, M. Morgan,N. Narendran, M. Nickleson, M. Rea,S. Sechrist, S. Vasconez, and K. Wilwol.Special acknowledgment to W. Chen,R. Davis, and Y. Ji for their contributionsto this publication.
No portion of this publication or the informa-tion contained herein may be duplicated orexcerpted in any way in other publications,databases, or any other medium withoutexpress written permission of RensselaerPolytechnic Institute. Making copies of all orpart of this publication for any purpose otherthan for undistributed personal use is aviolation of United States copyright laws. It isagainst the law to inaccurately presentinformation extracted from Specifier Reports forproduct publicity purposes.
The products described herein have not beentested for safety. The Lighting Research Centerand Rensselaer Polytechnic Institute make norepresentations whatsoever with regard tosafety of products, in whatever form orcombination used, and the results of testing setforth for your information cannot be regardedas a representation that the products are or arenot safe to use in any specific situation or thatthe particular product you purchase willconform to the results found in this report.
Lighting AnswersT8 Fluorescent Lamps, 1993; Multilayer Polarizer Panels, 1993; Task Lighting forOffices, 1994; Dimming Systems for High-Intensity Discharge Lamps, 1994; Electro-magnetic Interference Involving Fluorescent Lighting Systems, 1995; Power Quality,1995; Thermal Effects in 2'×4' Fluorescent Lighting Systems, 1995; T10 and T9Fluorescent Lamps, 1995; T5FT Lamps and Ballasts, 1996; Controlling Lightingwith Building Automation Systems, 1997
The National Lighting Product Informa-tion Program (NLPIP) was establishedin 1990 and is administered by theLighting Research Center at RensselaerPolytechnic Institute. The LightingResearch Center is a nonprofit educa-tional and research organizationdedicated to the advancement of light-ing knowledge.
NLPIP’s mission is to rapidly provide thebest information available on energy-efficient lighting products. NLPIP strivesto provide complete, current, and valu-able manufacturer-specific performancedata in useful formats to guide lightingdecisions. Priority is given to informationnot available or easily accessible fromother sources.
NLPIP tests lighting products accordingto accepted industry procedures. If pro-cedures are not available or applicable,NLPIP develops interim tests, focusingon those performance issues that areimportant to the lighting specifier andend user. The program does not acceptfunding from manufacturers.
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