H8 Fluorescent Lamps And Ballasts

a. General
o For typical construction of a fluorescent lamp, see the figure below.
o A fluorescent lamp is a low-pressure mercury electric discharge lamp.
o A fluorescent lamp consists of a glass tube filled with a mixture of argon gas and mercury vapour at low pressure.
o When current flows through the ionized gas between the electrodes, it emits ultraviolet (UV) radiation from the mercury arc.
o The UV radiation is converted to visible light by a fluorescent coating on the inside of the tube.
o The lamp is connected to the power source through a ballast, which provides the necessary starting voltage and operating current.
Typical Construction of a Linear Fluorescent Lamp Basic Types of Fluorescent Lamps


o Preheat lamps
o Instant start lamps
o Rapid start lamps
Preheat Lamps
o The cathodes of the lamp are preheated electrically for a few seconds before a high voltage is applied to start the lamp.
o The preheating is accomplished by the use of an automatic switch, called a “starter”, which applies current to the cathodes for sufficient time to heat them.
o The preheat lamps have a bi-pin (double-pin) base at each end.
o Preheat lamps operate normally in a preheat circuit (preheat ballast, starter, lamp and lamp holders).
o Preheat lamps can also be used in rapid start circuits.
o Preheat lamps are not widely used today
Instant Start Lamps
o The instant start lamp requires a high starting voltage, which is supplied by the ballast.
o Since there is no preheating of the cathodes, there is no need for a starter.
o Electrode heating is provided by the arc once it has been established.
o The instant start lamps have a single-pin base at each end of the bulb.
o A few instant start lamps have bi-pin bases, with the pins connected together inside the base.
o Instant start lamps operate normally only in an instant start circuit (instant start ballast, lamp and lamp holders).
Rapid Start Lamps
o The ballast quickly heats the cathodes causing sufficient ionization in the lamp for the arc to strike.
o The cathodes may or may not be continuously heated after lamp starting, depending on ballast design.
o Rapid start lamps start almost instantly (in one or two seconds).
o No starter is required - eliminating the time delay of preheat systems.
o Less voltage is required for starting than with instant start lamps, thus using smaller, more efficient ballasts.
o The rapid start lamps have a bi-pin (double-pin) base at each end.
o Rapid start lamps can also be used for dimming and flashing applications.
o Rapid start lamps operate normally only in a rapid start circuit (rapid start ballast, lamp, and lamp holders).
o Rapid start lamps are the most widely used fluorescent lamps.
Types of Rapid Start Lamps
o Linear fluorescent lamps – new types, both T8 and T5 sizes
o Linear fluorescents (430 mA for F40) - old types, primarily T12 size
o Energy saving fluorescents, primarily T12 size
o U-shaped fluorescents, in both T8 and T12 sizes
o Circular lamps, in T9 and T5 sizes
o High output lamps, available in T12, T8 and T5 sizes
o Very high output lamps (1500 mA), primarily T12 size
o Lamp diameters range from 5/8˝ to 2.5˝
Fluorescent Lamps

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T-5 miniature bi-pin (5/8˝ diameter)
T-12 medium bi-pin (11/2˝ diameter)
Medium bi-pin (11/2˝ diameter)
T-12 recessed double contact (11/2˝ diameter)
T-6 single-pin (3/4˝ diameter) SLIMLINE
T-6 single-pin (3/4˝ diameter) SLIMLINE
T-12 single-pin (11/2˝ diameter) SLIMLINE
T4, T-5
T-17 mogul bi-pin (21/8˝ diameter)
T-8 medium bi-pin (1˝ diameter)
High Output and Very High Output
Compact Fluorescent
U-Shape Circular

Lamp Designations
Bi-pin lamps (preheat, instant start, rapid start)
• Identified by wattage, bulb diameter and colour.
• Example: F40TI2/CW/ES
F : Fluorescent lamp
40 : Wattage (34 W for ES types)
T : Tubular bulb shape
12 : Maximum tube diameter - in eighths of an inch
(12/8 = 1.5˝)
CW : Cool white colour
Example: F32 T8/41K
F : Fluorescent lamp
32 : Wattage (32 W)
T : Tubular bulb shape
8 : Maximum tube diameter - in eighths of an inch
(8 x 1/8 = 1˝)
41K : 4,100 K, Cool white colour
Single-pin lamps (instant start)
• Identified by length and colour rather than wattage because they can operate at more than one wattage.
• Example: F96T12/WW
F : Fluorescent lamp
96 : Lamp length in inches
T : Tubular bulb shape
12 : Maximum tube diameter - in eighths of an
inch (12/8 = 1.5˝)
WW : Warm white colour
Lamp Lengths
Some typical lamp lengths are:
• F20 lamp - 24˝ (2´)
• F30 lamp - 36˝ (3´)
• F32 T8 lamp - 48˝ (4´) – becoming the industry standard
• F40 lamp - 48˝ (4´)
• F96 lamp - 96˝ (8´)
Colour Codes
(e.g., 841 = 80% CRI and 4100 Kelvin)
C50 : Chroma. 50 (5,000K, CR190+) 90+ 5000
C75 : Chroma 75 (7,500K, CR190+) 90+ 7500
CW : Cool White 62 4200
CWX : Cool White Deluxe 87 4100
D : Daylight 76 6500
LW : Lite White 48 4150
N : Natural 86 3600
SP : Spectrum Series 70+ varies
SPX : Spectrum Series Deluxe 80+ varies
WW : Warm White 52 3000
WWX : Warm White Deluxe 74 2950
741 : T8 Cool lamp colour 70+ 4100
735 : T8 Neutral lamp colour 70+ 3500
730 : T8 Warm lamp colour 70+ 3000
841 : T5 & T8 Cool lamp colour 85+ 4100
835 : T5 & T8 Neutral lamp colour 85+ 3500
830 : T5 & T8 Warm lamp colour 85+ 3000
Deluxe : Means better CRI, but with older style T12 lamps, also lower efficacy

Lamp Type Code
The lamp type code follows the colour code.
Lamp type codes are listed below.
• IS : Instant Start
• RS : Rapid Start
• HO : High Output
• VHO : Very High Output
• U : U-shaped
• WM : WattMiser (General Electric)
• SS : Super Saver
• EW : Econowatt (Philips)
General - A fluorescent luminaire consists of:
a ballast, usually shared by two lamps,
fixture and lense or louvers
Lamp Configuration - Linear, U-shape, circular or compact
Lamp Watts - 7 W to 215 W
Ballast Watts - varies according to type,
electromagnetic or electronic, and
Ballast Factor
Rated Average Life - 20,000 hours for typical F32T8 lamps
- 24,000 hour T8 lamps are available
- 20-24 times the life of a typical incandescent
Luminous Efficacy - 40 to 100 lumens per watt

Lamp Lumen - 70% to 90%
Depreciation Factor (LLD)
Colour Temperature - 2,700 K to 7,500 K
- Wide range of colour temperatures
Index (CRI)
Colour Rendering - 62 to 94
Warm-up Time - Instant
- Sensitive to extremes of temperature
- Slower than incandescent
Restrike Time - Immediate
Lamp Cost - Low
- Energy-saving and energy-efficient
lamps more expensive
Main Applications - Offices, commercial

Fluorescent Lamps
Rated Initial
Lamp Lumens Colour
Lamp Lamp Including Ballast Life Initial per Temp
Designation Watts 1 Lamp (2 Lamp) (hours) Lumens Watt Deg K CRI
Energy Saving, Rapid Start, Bi-Pin Base
F4OT12/…. /RS/….EW, SS or WM
CW 34 47 (81) 20,000 2,775 59.0 4,100 62
CWX 34 47 (81) 20,000 1,925 41.0 4,100 87
WW 34 47 (81) 20,000 2,825 60.1 3,000 52
D 34 47 (81) 20,000 2,350 50.0 6,500 75
LW 34 47 (81) 20,000 2,925 62.2 4,160 48
3OU 34 47 (81) 20,000 2,925 62.2 3,000 85
35U 34 47 (81) 20,000 2,925 62.2 3,500 85
41U 34 47 (81) 20,000 2,925 62.2 4,100 85
5OU 34 47 (81) 20,000 2,925 62.2 5,000 85
SPEC30 34 47 (81) 20,000 2,925 62.2 3,000 70
SPEC35 34 47 (81) 20,000 2,925 62.2 3,500 73
SPEC41 34 47 (81) 20,000 2,925 62.2 4,100 70
Notes: • Refer to lamp manufacturers for colours other than shown here.
• Rated Average Life for fluorescent lamps is based on three hours per start.
• Mean Lumens for fluorescent lamps are listed at 40% of lamp life.
See Also • Lamp manufacturers’ catalogues.

Rated Initial Mean
Including Lamp Lumens Lumens Colour
Lamp Lamp Ballast Life Initial per Mean per Temp
Designation Watts 1 Lamp (2 Lamp) (hrs) Lumens Watt Lumens Watt Deg K CRI LLD
Compact Fluorescent
7W + 7 10 10,000 400 40.0 2,700 81 0.80
9W + 9 10 10,000 600 60.0 2,700 81 0.80
13W + 13 17 10,000 900 52.9 2,700 81 0.80
Circlite (retrofit for incandescent)
FCA22/SW + 22 22 10,000 870 39.5
FCA44/SW + 44 44 7,500 1,750 39.8
Rapid Start Circline
FC8/CW/RS + 1 22 27 12.000 1,050 38.9 805 29.8 4,300 62 0.72
FC12/CW/RS + 32 44 12,000 1,800 40.9 1,465 33.3 4,300 62 0.82
FC16/CW/RS + 40 56 12,000 2,500 44.6 1,910 34.1 4,300 62 0.77
Instant Start, 200 milliamp, Single Pin Base
F72T8/CW 38 55 (100) 7,500 3,100 56.4 2,700 49.1 4,300 62 0.83
F96T8/CW 50 70 (130) 7,500 4,200 60.0 3,860 55.1 4,300 62 0.89
Instant Start, 430 milliamp, Single Pin Base
F48Tl2/CW 39 65 (104) 9,000 3,000 46.2 2,760 42.5 4,3DO 62 0.82
F48TI2/LW 30 55 (84) 9,000 2,675 48.6 2,460 44.7 4,100 49 0.82
F72Tl2/CW 55 80 (150) 12,000 4,600 57.5 4,320 52.9 4,300 62 0.89
F96T12/CW 75 97 (172) 12,000 6,300 64.9 5,8DO 59.8 4,300 49 0.89
F96TI2/LW 60 82 (142) 12,000 6.000 73.2 5,430 66.2 4,100 49 0.89
Rapid Start, 430 milliamp, Bi-pin Base
F30T12/CW/RS 30 46 (76) 18,000 2,300 50.0 2,010 43.7 4,300 62 0.81
cool white 40 53 (93) 20,000 3,150 59.4 2.715 51.2 4,300 62 0.84
cool while 40 53 (93) 20,000 2,220 41.5 1,800 34.0 4,200 87 0.84
warm white 40 53 (93) 20,000 3,200 60.4 2,715 51.2 3,000 52 0.84
warm white 40 53 (93) 20,000 2,150 40.6 1,765 33.3 3,100 73 0.84
daylight 40 53 (93) 20,000 2,600 49.1 2,245 42.4 6,500 75 0.84

Rated Initial Mean
Including Lamp Lumens Lumens Colour
Lamp Lamp Ballast Life Initial per Mean per Temp
Designation Watts 1 Lamp (2 Lamp) (hrs) Lumens Watt Lumens Watt Deg K CRI LLD
lite white 35 48 (83) 20,000 3,050 63.5 4,160 48 0.84
lite white deluxe 34 47 (81) 20,000 3.050 64.9 4,100 67 0.84
full spectrum 5000 40 53 (93) 20,000 2,200 41.5 1,850 34.9 5.000 92 0.84
full spectrum 7500 40 53 (93) 20,000 2,000 37.7 1,685 31.8 7,500 94 0.84
prime colour 3000 40 53 (93) 20,000 3,400 64.2 3,000 85 0.84
prime colour 4000 40 53 (93) 20,000 3,400 64.2 4,000 85 0.84
*indicates low power factor ballast only available
Rapid Start T8, Bi-pin Base
F032/730 32 30 (59) 20,000 2,800 93.0 2,520 84.0 3,000 75 0.90
F032/830 32 30 (59) 20,000 2,950 98.0 2,714 90.0 3,000 82 0.92
F032/830 6 30 (59) 24,000 2,900 96.6 2,755 91.8 3,000 85 0.95
F032/830/XP 30 (59) 24,000 3,000 100 2,850 95.0 3,000 85 0.95
Hiqh Output Rapid Start, 800 milliamp, Recessed Double Contact Base
F48TI2/CW/HO 60 85 (146) 12,000 4,300 50.6 3,740 44.0 4,300 62 0.82
F72Tl2/CW/HO 85 106 (200) 12,000 6,650 62.7 5,785 54.6 4,300 62 0.82
F96Tl2/CW/HO 110 140 (252) 12,000 9,200 65.7 8,005 57.2 4,300 62 0.82
F96TI2/LW/HO 95 119 (231) 12,000 9,100 76.5 7,915 66.5 4,160 48 0.82
F96Tl2/LWX/HO 95 119 (231) 12,000 9,100 76.5 4,100 67 0.82
Very High Output Rapid Start, 1500 milliamp, Recessed Double Contact Base
F48TI2/CW/VH0 110 146 (252) 10,000 6,250 42.8 4,750 32.5 4,300 62 0.69
F72Tl2/CW/VHO 165 213 (326) 10,000 9,900 46.5 7,920 37.2 4,300 62 0.72
F96Tl2/CW/VHO 215 260 (450) 10,000 14,500 55.8 11,600 44.6 4,300 62 0.72
F96PG17/CW 215 260 (450) 12,000 16,000 61.5 12,800 49.2 4,300 62 0.69
F96PG17/LW 185 230 (390) 12,000 14,900 64.8 11,325 49.2 4,160 48 0.69
*indicates low power factor ballast only available
Notes: Some lamps listed here are no longer commercially available, notably the full output F40/CW lamp; they are
included here for comparison only.

b. Premium T-8 Lamps
Lamp manufacturers now offer premium grade T-8 lamps for special applications where exceptional colour, longer life and improved lumen output are required.
Standard F32 T-8 Lamp: 20,000 hrs, 82 CRI, 2,950 initial lumens, 98.3 initial lm/W
Premium F32 T-8 Lamp: 30,000 hrs, 86 CRI, 3,100 initial lumens, 103.3 initial lm/W
c. Low-Wattage T-8 Lamps
Lamp manufacturers now offer reduced output or low-wattage T-8 lamps for increased savings on retrofit projects, or for new construction.
Standard F32 T-8 Lamp: 20,000 hrs, 82 CRI, 2,950 initial lumens, up to 80 lm/W depending on ballast
Low-Wattage F28 T-8 Lamp: 24,000 hrs, 82 CRI, 2,562 initial lumens, up to 93 lm/W, depending on ballast
• These lamps have some limitations, for example, they cannot be dimmed, and don’t operate in cool temperatures (<60˚F)
• Some operate on programmed start ballasts and all operate in instant start ballasts.
d. T-5 and T5-HO Fluorescent Lamps
• Lamp manufacturers now offer T-5 fluorescent lamps in both standard and High Output (HO) versions.
• The smaller diameter tube yields a more compact lumen package, which is easier to control.
• T-5 fluorescent lamps are available in various lengths and wattages from 14 W to 80 W, and in a circline version in 22 W, 40 W, and 55 W.
• T-5 lamps are nominal length lamps, which means that they cannot be retrofit into fixtures using standard T-12 or T-8 lamps. Therefore, they are generally used for re-design or new construction projects.
• T-5 fluorescent lamps require the use of electronic ballasts and unique sockets.
• T-5 lamps are driving miniaturization and can be used in indirect applications.
• T5-HO is an increasingly popular fluorescent lamp; primarily used in normal to high bay applications, big box retail, warehouse and distribution centres, industrial applications and gymnasiums. T5-HO are also dimmable and operate on instant start ballasts.
• T5 and T5-HO have maximum light output at higher ambient temperatures.
Standard T-5 Lamps: 14 W, 24˝ (nom), 20,000 hrs, 82 CRI, 1,350 initial lumens
21 W, 36˝ (nom), 20,000 hrs, 82 CRI, 2, 100 initial lumens
28 W, 48˝ (nom), 20,000 hrs, 82 CRI, 2,900 initial lumens
35 W, 60˝ (nom), 20,000 hrs, 82 CRI, 3,650 initial lumens
High Output T-5 Lamps: 24 W, 24˝ (nom), 20,000 hrs, 82 CRI, 2,000 initial lumens
39 W, 36˝ (nom), 20,000 hrs, 82 CRI, 3,500 initial lumens
54 W, 48˝ (nom), 20,000 hrs, 82 CRI, 5,000 initial lumens
e. Fluorescent Fixture Reflectors
General Description
Fluorescent fixture reflectors are sheets of aluminum placed inside fluorescent fixtures, which divert light directed toward the ceiling down toward the work area.
• Illustration of a recessed reflector for a 2´ x 4´ fixture, with removal of two lamps.

Before Installation of the Reflector:


After Installation of the Reflector:


Physical Data
• There are three basic types of reflectors:
- Anodized aluminum or steel reflectors – in which the surface is painted with a highly reflective
electrostatic or powder-epoxy finish.
- Anodized aluminum reflectors - in which the aluminum surface is treated (polished) electrochemically.
- Silver film reflectors - in which a thin film of silver is laminated to an aluminum substrate.
• The reflector finish can be high gloss paint, specular (mirror-like), semi-specular, or diff use (matt).
• The reflector shape is specially designed to optimize light distribution (custom-designed by the supplier).
• Reflectors are made in the following sizes:
- Single reflectors - 4´ or 8´ long, one-lamp use
- Double reflectors - 4´ or 8´ long, two-lamp use
- Recessed reflectors - for 2´ x 2´ or 2´ x 4´
Technical Data
• The average total reflectivity for anodized aluminum reflectors is about 90% to 91%.
• The average total reflectivity for silver film reflectors is about 94% to 97%.
• Life expectancy of a silver film reflector is about 15 years.
• Life expectancy of an anodized aluminum reflector is about 20 years.
• Reflectors are used for lighting energy conservation.
• Reflectors are used for fixture retrofitting or in new energy efficient fixtures.
• A typical application is the installation of a recessed reflector in a 2´ x 4´ fixture, with removal of two of the
four tubes.
• In most instances, it is necessary to re-centre the two remaining lamps in the fixture to avoid dark spots.
• The reflector creates the image of a lamp in the place of the removed lamp; this allows delamping without creating dark spots.
• The light output of a retrofitted fixture with half the lamps removed typically decreases by about 35%, depending on reflector material and design.
• Cleaning and relamping at the same time increases light output by 5% to 20%.
• Costs depend on the type, size and design of the reflector.
• Reduces lighting power consumption;
• Improves luminous efficacy in the work area;
• Reduces cooling load, in the case of delamping;
• Extends ballast and lamp life by decreasing operating temperature;
• Fewer lamps and fixtures are required;
• Reduces maintenance costs.
• May have long payback period;
• Not cost-effective if fixtures of different size and type are involved;
• May create a ‘cave effect’ in some situations, causing walls to appear dark at the top because the light is focused downwards.
• Has clear benefits from a lighting efficiency point of view.
• Should be compared to other lighting conservation measures.

a. General
A ballast is a device used with a gas discharge lamp to provide the necessary starting and operating electrical conditions.
o The ballast supplies the right voltage to start and operate the lamp.
o The ballast limits current to a gas discharge lamp during operation - the resistance of a gas discharge lamp becomes negligible once the arc has been struck.
o The ballast prevents any voltage or current fluctuations caused by the arc discharge from reflecting into the line circuit.
o The ballast compensates for the low power factor characteristic of the arc discharge.
Ballast Construction
o A simple standard ballast is a core and coil assembly.
o The core is made of laminated transformer steel.
o The coil consists of copper or aluminum wire which is wound around the core.
o The core-coil assembly is impregnated with a nonconductor to provide electrical insulation and aid in heat dissipation.
Capacitors may be included in the ballast circuit to assist in providing sufficient voltage, start the lamp, and/or correct power factor.
o Some ballasts are housed inside the lighting fixture.

Simple Ballast Illustrations

Typical Wiring Diagrams

Ballast Losses
o A ballast, as an electric circuit, has electric energy losses.
o Ballast losses are obtained from catalogues of ballast manufacturers.
o Energy efficient ballasts have lower losses.
o Basic types of ballasts based on ballast construction and efficiency are:
- Energy efficient ballasts (core-coil magnetic);
- Electronic ballasts (solid-state);
- Standard magnetic ballast (core-coil design).
- Ballasts are also classified by the type and function of their electric circuit.
- Note that electro-magnetic fluorescent ballasts are gradually being removed from the marketplace by energy regulations.
- Each ballast is designed to be used with a specific type and size (wattage) of lamp.
- The lamp type and size compatible with the ballast are listed on the ballast label.
o Ballasts should meet ANSI (American National Standards Institute) specifications for proper lamp performance. The Canadian standard for ballast efficiency is CAN/CSA-C654-M91 Fluorescent Lamp Ballast Efficacy Measurements.
o The CBMA (Certified Ballast Manufacturers Association) label indicates that the ballast has been tested and meets ANSI specifications.
o The UL (Underwriters Laboratories) label indicates that the ballast has been tested and meets UL safety criteria (US standard) as well as the Canadian CAN/CSA-C654-M91 criteria.
o The CSA (Canadian Standards Association) label indicates that the ballast has been tested and meets CSA safety criteria.
o Under the North American Free Trade Agreement, both UL and CSA can certify electrical products for sale in both countries.
Thermal Protection
o The NEC (US National Electrical Code) and the Canadian Electrical Code require that all indoor ballasts must be thermally protected.
o This is accomplished by a thermal switch in the ballast which turns power off above a maximum temperature (1050˚C approximately).
o Ballasts meeting this standard for protection are designated Class P.
o A cycling ballast, which turns power off and on, indicates an overheating problem.
Sound Ratings
o All core-coil ballasts produce a sound commonly described as a “hum”.
o Manufacturers give the ballasts a sound rating from A to F
o An A ballast produces the least hum, and should be used in quiet areas (offices, homes).
o An F ballast produces the most audible hum, and may be used in places where noise is acceptable (factories, outdoors).
Ballast Life
o Most ballasts are designed for about 50,000 hours under standard conditions.
o If ballast and lamp heat is not dissipated properly ballast life is reduced.
o An 8-10˚C increase over rated temperature on the case will cut ballast life in half.
o Ballasts are rated typically for 75˚C. 90˚C ballasts are a special design called “Extreme Temp”. Some manufacturers list 8˚C instead of 10˚C.
o Similarly, a 100˚C decrease will approximately double ballast life.
b. Electronic Ballasts for Gas Discharge Lamps
Typical Circuit Component Diagram


o Some ballasts have fewer components.
o Some ballasts have components to reduce total harmonic distortion, improve power factor and provide thermal protection.
General Description
o A rapid start ballast starts one or more gas discharge lamps by first heating the electrodes of the lamps to the proper electron emission temperature before initiating the arc.
o An instant start ballast does not preheat the electrodes but initiates the arc by a higher starting voltage.
o A modified start ballast starts the lamp in the same way as the rapid start ballast. It then reduces or cuts off the electrode heating voltage after the lamp arc has stabilized.
o Both types of ballast stabilize the arc by limiting the current to proper levels.
o Older technology (i.e., electromagnetic) ballasts are made of laminated cores wound with copper or luminum wires; some have capacitors to control voltage and/or to correct power factor.
o Electromagnetic ballasts operate the lamps at line frequency, 60 Hz.
o Electronic ballasts for fluorescent lamps have electronic or solid-state components.
o Electronic ballasts operate the lamps at a high current frequency, typically from 25-50 kHz.
o Electronic ballasts in both the rapid start, instant start and ‘program start’ modes are available.
o Operation of rapid start lamps by instant start or modified start ballasts can potentially shorten lamp life if combined with other control technologies such as occupancy sensors.
Refer to the ballast and lamp manufacturers’ data.
o In comparison with the electromagnetic ballast, the electronic ballast weighs less, operates at lower temperatures and at a lower noise level, and is more energy efficient, but costs more.
o It is essential to match the electrical characteristics of both lamps and ballasts.
Technical Data
o Models are available for one-lamp, two-lamp, three-lamp or four-lamp fixtures.
o Available in 120 volts, 277 volts and 347 volts. Some ballasts are now available for universal voltage, i.e., 120 V to 277 V, and less common voltages such as 240 V.
o Ballast specification is based on: number of lamps, lamp type (F32T8/841 or other) and line voltage.
o Example: two-lamp F32T8/841 120V electronic ballast.
o Some electronic ballasts are dimmable.
o The efficacy of electronic ballasts is 21% to 43% better than electromagnetic ballasts.
o Total harmonic distortion (THD) indicates the strength of electromagnetic noise generated.
o Lower ballast temperature means lower electrical losses and a smaller cooling load.
Total Harmonic Distortion
o Harmonics are frequencies that are integral multiples of the fundamental frequency.
o For a 60 Hz fundamental frequency, the second harmonic is 120 Hz, and the third is 180 Hz.
o Harmonics can be present in voltage and/or current.
o Harmonics occur whenever the wave shape is distorted from a pure sine wave.
o Electric utilities supply voltage and current very close to the sinusoidal wave form.
o If the user’s load is nonlinear, drawing short pulses of current within each sine wave cycle, the sinusoidal current wave shape will be distorted and a harmonic current will be present.
o The characteristics of the nonlinear load determine the form of the distortion, the magnitude of each harmonic and the corresponding harmonic current.
o Total current is a combination of the fundamental frequency and a contribution from each of the harmonics.
o THD in the current is the root mean square (rms) of all the harmonic currents as a percentage of the fundamental current, and is defined as follows:
THD = _sum of squares of rms magnitudes of all harmonics* X 100% rms magnitude of fundamental

  • Does not include the fundamental.

o IEEE Standard 519-1981 refers to the Distortion Factor (DF) which equals the THD. However, THD is the preferred term in this guide as it is more descriptive.
o Most electromagnetic ballasts have THD between 18% and 35%.
o Electronic ballasts generate less than 32% THD. Most of them are below 20%. Some are below 10%.
o Due to higher efficiency, the T8 electronic ballast system typically draws 30% less current than the conventional electromagnetic ballast system.
Electromagnetic Interference (EMI) or Radio Frequency Interference (RFI)
o EMI/RFI may cause interference with communication equipment, such as radio, TV, computer.
o Fluorescent lamps energized by electromagnetic or electronic ballasts radiate EMI directly into the air.
o EMI from the lamps may feed back to the line conductors via the ballasts.
o EMI at the electronic ballast fundamental frequency and its harmonics propagate from the ballast’s electronic circuits to the line conductors. This EMI may interfere with other electrical equipment on the same distribution network.
o EMI may radiate from the line conductor into the air.
o EMI may be radiated from the high frequency electronic components of the electronic ballast.
o In the US, electronic ballasts must comply with Federal Communications Commission Part 18, Subpart C, Class A for industrial and commercial applications, or Class B for residential applications. As yet no Canadian standard has been set.
Power Factor
o Power factor can be calculated by two methods:
- Wattage (W), voltage (V) and current (I)
- Wattage (W) and reactive power (VAR).
o If calculated correctly – the results should be the same using both methods.
o A low power factor will increase the kVA demand component of your electricity bill for a given lighting load
Rated Average Life
o Ballasts are designed to operate for about 50,000 hours.
o Lower ballast operating temperature reduces air-conditioning load.
o The early models had lower reliability than the present ballasts.
o When used with light sensors, dimmable electronic ballasts can reduce the lighting load by providing just the required light level, if other light sources exist.
o Similarly, an energy management and control system uses dimmable ballasts to partially shed the lighting load.