Module 2 Light Sources and Ballasts

Fundamentals of Lighting

Module 2: Learning Objectives

Welcome to the second module in Lighting Fundamentals. After successfully completing Module 2, students will:

• Understand the basic operation and performance characteristics of electric light sources

• Understand how discharge light sources operate as part of a lamp/ballast system

• Be able to identify commonly used electric light sources and understand where and how they are applied

Ready to begin? Let’s start with…..

Brief History of Light Sources

1900 --- 1950 --- 2000 ---

1880 Thomas Edison patents a carbon

filament vacuum incandescent lamp.

1910 The first gas discharge source,

“NEON”, is invented. 1930s Mercury Vapor (MV), Low Pressure

Sodium (LPS), and the first fluorescent sources are developed.

1960s High Pressure Sodium (HPS),

Metal Halide (MH) & color-corrected MV lamps introduced.

1970s Color-improved HPS and MH. High

CRI fluorescent lamps. Electronic fluorescent ballasts developed.

1980s CFL, T10 & T8 fluorescent lamps

introduced. LED & Electroluminescent exit signs. Energy-efficient magnetic fluorescent ballasts.

1990s High-CRI HPS, Ceramic MH,

Induction, Sulfur, T5 & T2, and reduced mercury fluorescent lamps, electronic HID ballasts introduced. High output blue LED developed

2000s Large scale market acceptance of

CFLs; proliferation of “white” LEDs and colored LEDs for general illumination and signage;

The Incandescent Lamp

Fluorescent 60 - 109 LPW

Mercury 40 - 58 LPW

Metal Halide 67 - 115 LPW

High Pressure Sodium 71 - 145 LPW

Lumens Per Watt - Including Ballast

0 20 40 80 100 12060 140 160 180 200

Low Pressure Sodium 100 - 180 LPW

Incandescent/Halogen 10 - 30 LPW

Lamp Efficacy

Incandescent Lamps

Definition: an incandescent lamp (generally known as a “filament lamp”) produces light using the principle of incandescence – when a tungsten filament is sufficiently heated by passing electric current through it, it will glow and emit light.

Types: there are two general families of filament lamps: incandescent and halogen (more on halogen a little later).

Filament lamps are still the most common light source. They are available in a myriad of shapes, sizes, light output, and cost. Anybody for a flame-shaped yellow bug light?

Advantages

• Low initial cost

• High CRI

• Instant on

• Not ambient temperature

sensitive

• No ballast

• Large variety of shapes, sizes,

bases, wattages

• Ease of dimming

• Wattage Interchangeability

Disadvantages

• Lowest efficacy (10-20 lpw)

• High infrared output (heat)

• Short life (750-1000 hours)

• Voltage sensitivity

• Environmental impact

Incandescent Advantages & Disadvantages

Tungsten Filament

SupportsStem PressFuse, within the

Base

Envelope (Bulb)

Gas

lead-in wires

Construction

PS A G A-15-19 P S

Linear2-base

C-7 S-11 B10 F T

R ER PAR 38Med. Skt.

PAR 46, 56, 64 PAR 38, 46Med. Side Prong

PAR 46, 56, 64Screw Term.

Lamp Shapes

Lamp Size Designations

Mortality Curves

0 40 60 80 100 120 140 160 1800

20

40

60

80

100

Percent Survivors

Percent Rated Life

Lamp Life

50% Survivors

Tungsten Halogen Lamps

Tungsten Halogen Lamps

Tungsten Halogen lamps

• An extension of the incandescent family

•Often called “quartz halogen” or just “halogen” lamps

•They have a more complex construction in order to increase life, efficacy, and color temperature (“whiter” light).

•Many halogen lamps are a “lamp within a lamp” – a small halogen “capsule” is mounted in a reflector

•Halogen lamps can be either line voltage (120V) or low voltage (12V).

The Tungsten Halogen Cycle

The filament is affected by the halogen cycle

“Tungsten Spikes”

The filament is affected by the halogen cycle

“Tungsten Spikes”

Halogen Gasses:IodineChlorineFluorineBromine

Regenerative cycle puts thetungsten back onto the filament

Halogen

Materials - StrengthPure quartz or hard glass bulb is strong and has a high melting point

Standard Incandescent

• Large Surface Area to Minimize Bulb Blackening

• 750 - 1000 Hour Life

• Atmospheric Pressure

Halogen

• Compact, High Pressure Capsule

• High Density Fill Gases

• Halogen Cycle

Standard Incandescent vs. Halogen

Types of Halogen Lamps

Line Voltage

PAR 20, 30, and 38

Halogen “A” lamps

Double-ended

Bayonet base

Low Voltage

Bi-pin Halogen

MR-11 and MR-16

AR-70, AR-111

PAR Halogen A-lamps

Double-ended

Bayonet base

Bi-pin

MR-16

AR-111

More types of halogen lamps

PAR30 Long Neck

PAR30 PAR20

PAR38

DEQ

MR 16

Advantages of Tungsten Halogen Lamps

• Higher Efficacy: 15-30 lpw

(compared to incandescent)

• High Luminaire Efficiency

• 2X – 3X Life vs. Standard

Incandescent

• Excellent Optical Control

• Whiter Light: 3000K

• Easily Dimmable

• Wide variety of shapes and

sizes

Halogen PAR Technology "A Lamp Within a Lamp"

Medium Skirted Base

Reflector

Lens Bondedor Flame Sealed

Halogen Capsule

Common Line Voltage Halogen Lamp

Approx. 19 Layersof

Optical Coating

Infra-red Radiation(Heat)

Light

Glass Substrate

MR-16 Low Voltage Lamp

Dichroic reflector coatings

Low voltage halogen capsule (usually 12V)

Bi-Pin base

Advantages of Low Voltage

• Smaller filaments provide improved beam control

• Typically longer life than line voltage lamps

• Some types have higher color temperature

• Lamps are smaller in size

Filament Wire Diameter as a Factor of Design Voltage

100 Watts

12 Volt

120 Volt

220 Volt

Low Voltages Use Thicker,More Rugged Filaments

Human Hair35 m Diameter

270 m Diameter

70 m Diameter

45 m Diameter

Tungsten Halogen Filaments

60.0

65.0

70.0

75.0

80.0

85.0

90.0

95.0

100.0

105.0

0 20 40 60 80 100 120

Percent Rated Life

Per

cen

t In

itia

l L

um

ens

Metal Halide

Incandescent

Fluorescent

Lumen Maintenance

Tungsten Halogen

IR (Infra-Red) Halogen Lamps

Halogen IR lamps have increased efficacy

over standard halogen

– IR-reflective coating on OUTSIDE of bulb

– Reflects IR energy (better known as

“heat”) back onto the filament

– Bulb is shaped to maximize reflected IR

back onto the filament

– Filament reaches operating temperature

at lower current (and therefore less

power) than standard halogen

82% Infrared Heat

Lamp dynamics IR coating

18% Visible Light

Can Halogen Lamps be dimmed?

• Halogen and Dimming

– The halogen cycle only works when the inside wall of the capsule is above 250º C. If you dim a halogen lamp too low, the cycle stops and the inside of the capsule becomes gray. To fix the problem, just operate at full power for a short while and the capsule will be “cleaned”.

Spectral Characteristics

•Filament lamps have a “continuous” spectrum

•By definition, for warm sources, the CRI is 100

•Strong in red/orange

•Weak in blue

Fluorescent Lamps

Lamp Efficacy

Fluorescent 60 - 109 LPW

Mercury 40 - 58 LPW

Metal Halide 67 - 115 LPW

High Pressure Sodium 71 - 145 LPW

Lumens Per Watt - Including Ballast

0 20 40 80 100 12060 140 160 180 200

Low Pressure Sodium 100 - 180 LPW

Incandescent 10 - 30 LPW

Fluorescent Advantages and Disadvantages

Advantages

•High efficacy

•Long life

•Good CRI

•Variety of Color Temperatures

•Low cost per lumen

•Wide array of fixture types

•Low glare source

•Dimmable

Disadvantages

•Requires a ballast

•Difficult to focus – not a point source

•System cost (lamp and ballast) higher than filament sources

•Fixtures are large

•Temperature sensitivity

•Life affected by switching cycles

Construction & Operation

Phosphor Visible Light

Hot CathodeElectron

Mercury Atom

Ultraviolet Radiation

Bulb

Base

Argon

General Categories of Fluorescent Lamps

Linear fluorescent

• Most common for general lighting

Compact fluorescent

• Commonly used as replacement for incandescent

Electrodeless lamps

• More recent development – used as replacement for some HID lamps

Phosphor Coatings

Phosphor

• A substance that converts one wavelength to another

• Typically, inorganic compounds that “fluoresce” when exposed to 254 nm

radiation

• Typically blended to produce various colors or versions of “white”

“Halo” phosphors

• Calcium halophosphate compounds

• Inexpensive

Phosphor Coatings

“Tri” phosphors

• Also called “rare earth” phosphors

• Many are compounds of “rare earth” elements

• Expensive

Lamp Circuits

There are several types of fluorescent lamp circuits:

•Preheat

• Oldest type; not in common use today

•Rapid Start

• Mostly used in T12, T12 HO, and T12 VHO systems; not energy efficient

•Instant Start

• Most popular for T8 systems

• Low cost and energy efficient

•Programmed Start

• “Softest” starting method; allows frequent switching and long life

Fluorescent Lamp Identification

Example: 4-foot T8 lamp

F32T8/735F = Fluorescent

32 = Nominal Lamp Wattage

T = Tubular

8 = Bulb diameter in eighths of an inch

7 = 700 series phosphor – CRI between 70 and 79

35 = 3500K CCT

Lamp Lumen Depreciation*

* Also known as “lumen maintenance”

5060708090

100

0 20 40 60 80 100

Percent of Average Rated Life

Per

cent

of I

nitia

l Lu

men

sT8 (265 mA)

T12 (425 mA)

T12 (430 mA)

T12 (800 mA)

T12 (1500 mA)

IES LLD factor is at 40% of rated life

Lamp Life

•Average rated life can vary from 6000 hours for some compact fluorescent lamps to 24,000 hours for some T8 lamps.

•Lamp life is based on a burn cycle of 3 hours on and 20 minutes off.

•With longer “on” cycles, life can be as high as 36,000 hours for some T8 lamps.

•As with incandescent, average rated life is based on 50% survivors of a large sample size.

Lamp type Life,

hours Compact fluorescent

Screw base

6,000

Compact fluorescent

Pin base

10,000

F40 CW/RS 20,000

F96T12/HO 12,000

F32T8 RE 24,000

F96T8/HO 18,000

F28T5 20,000

Electrodeless

Fluorescent

60,000+

Starting Cycles

Per

cen

t o

f R

ated

Lif

e

100

150

200

0 5 10 15 20Hours per Start

ANSI cycle - 3 hours on, 20 minutes off

Effect of Starting Frequency on Lamp Life

Temperature Effects

0102030405060708090

100110

5 10 15 20 25 30 35 40 45 50 55AMBIENT TEMPERATURE oC

RE

LA

TIV

E L

IGH

T O

UT

PU

T

T5

T8

T8/T5 LUMEN OUTPUT VS. TEMPERATURE

Spectral Characteristics of Fluorescent Lamps

Most contemporary fluorescent lamps (tri-phosphor types) have a “discontinuous” or “line” color spectrum

Different ratios of the red, green, and blue phosphor produce the variety of CCTs

CCT typically 3000K – 4100K

CRI typically 70-86

Electrodeless Fluorescent Lamps

Developed in the 1990’s

Design eliminates one failure mode of standard fluorescent lamps: the cathode

Operates on the principle of induction

Life from 15,000 hours (self-ballasted) to 60,000 hours.

Life based on lumen maintenance and/or ballast life

Cost higher than for standard fluorescent

Used in areas where lighting maintenance cost is high – low-bay industrial, street lighting, signage, tunnel/bridge, etc.

Fluorescent Lamp Ballasts

Fluorescent Lamp Ballasts

•Provide necessary electrical conditions to start and operate lamps

•Two general categories – electromagnetic (or just “magnetic”) and electronic

•Almost all new fluorescent fixtures today employ electronic ballasts

•Lamps and ballasts are generally matched to ensure electrical compatibility

CoilsMade of wound

copper oraluminum wire.

Thermal Switch(Class P)

CoreConsists of stacked steel plates laminatedtogether. With the coils, transforms thecurrent to control the lamps.

CapacitorFor power factor correction, phasedisplacement and current limiting. Foundonly in high power factor ballasts.

Electronic Ballast

Electro-magnetic Ballast

0

20

40

60

80

100

120

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

2014

2015

Magnetic

Electronic

North American Linear Fluorescent Ballast Market Transformation

SourceUS Census – 2005

Characteristics of Fluorescent Lamp Ballasts

Electromagnetic

•Simple construction; few components

•Large and heavy

•Low energy efficiency

•Typically only operate 1 or 2 lamps

•Potentially noticeable flicker

•Potentially audible noise

•Mostly found in older T12 fixtures and outdoor applications

•Difficult to integrate into automated control systems

•Market decreasing rapidly

Electronic

•Greater number of components

•Smaller and lighter than magnetic

•More energy efficient – lower losses and operates lamp more efficiently

•No flicker due to high frequency operation

•Used in majority of new T8, T5, and CF fixtures

•Variety of operation – rapid start, instant start, programmed start, dimmable

•Can operate up to 4 lamps

•Parallel operation

•Easily integrated into control systems

•Available with several different ballast factors

•Universal input voltage

•Cost effective

Ballast Factor

Definition:

Ratio of lamp lumens when operated on a commercial ballast (actual lumens) to the lamp lumens when operated on a reference ballast (catalog lumens)

B.F. = lamp lumens on commercial ballast lamp lumens on reference ballast

Ballast Factor Ranges:

Can vary from 0.60 to 1.28, but normally listed as 0.78 (“Low”), 0.88 (“Normal”), and 1.20 (“High”).

Application Examples:

For retrofit from T12 to T8 lamps, ballast factor can be used to “tune” the light levels relative to the original level. If original level is too high, low ballast factor ballast can be used to increase energy savings (rather than de-lamp).

For new fixtures, high ballast factor ballast might allow use of 2-lamp fixture rather than 3-lamp fixture.

System Efficacy

For discharge light sources, there are actually two efficacy metrics:

•Lamp efficacy – as we have learned, nominal lamp lumens per nominal lamp watts. However, when the power losses and operating characteristics of the ballast are considered (type of circuit and ballast factor), then a second, more useful metric is used:

•System efficacy – actual lamp lumens per total system wattage. The actual lamp lumens in this case includes adjustment for ballast factor. Total system wattage is defined as the input watts to the ballast which includes lamp operating wattage and ballast power losses.

High Intensity Discharge (HID) Lamps

Lamp Efficacy

Fluorescent 60 - 109 LPW

Mercury 40 - 58 LPW

Metal Halide 67 - 115 LPW

High Pressure Sodium 71 - 145 LPW

Lumens Per Watt - Including Ballast

0 20 40 80 100 12060 140 160 180 200

Low Pressure Sodium 100 - 180 LPW

Incandescent 10 - 30 LPW

Types of HID lamps

Mercury

•Old technology; soon obsolete for general lighting

Metal Halide (MH)

•Popular choice for “white” light source•Used both for interior and exterior

High Pressure Sodium (HPS)

•Used mainly for outdoor street and area lighting•Higher efficacy than MH

Low Pressure Sodium (LPS)

•Highest efficacy of all HID sources•Monochromatic yellow

Mercury Lamps

• Oldest HID technology

• Lowest efficacy of HID types

– Not much better than halogen

• Poor – Fair CRI

• High CCT

• Poor lumen maintenance

• Strong color shift as they age – turns green!

• Basically obsolete due to recent legislation banning mercury ballasts

– Allows replacement lamps, but no new fixtures

Metal Halide Lamps

Enhanced version of the mercury lamp

Elements are added to the arc tube to improve performance (e.g., sodium, scandium, along with argon gas)

Most complex of the HID sources

Popularity growing due to variety of types, wattages, color temperatures, etc.

MH Advantages and Disadvantages

Advantages

High light output (“white” light)

High efficacy

Long life (6,000 – 20,000 hours)

Virtual point source for good optical control

Premium types available with good color (80-95 CRI) and improved lumen maintenance (due to pulse start, ceramic arc tube)

Large range of wattages (39W – 1500W)

Dimmability (although limited)

Disadvantages

Some color shift over life

Possible color inconsistency lamp to lamp

Sensitive to burning position

Higher cost

Some MH types and certain applications should be group relamped.

Limited dimmability

Limited availability of electronic ballasts (costly if available)

Arc Tube

• Light source• Quartz or PCA (Polycrystalline Alumina)

– Electrodes, radiating elements, gas fill

Mount

• Supports/Centers arc tube in Outer Jacket (aka: bulb)

• Provides electrical path to arc tube• Frame, straps, getter, resistor, bi-metal

switch, etc.

– Stainless steel, nickel plated steel

Stem

• Allows for hermetic seal of outer bulb• Hard Glass (Borosilicate)• Provides electrical path to Mount

– Flare, lead wires and exhaust tube

Key Lamp Components

Outer Jacket (OJ) - Envelope

• Provides clean/temp controlled environment for arc tube

• Filters out UV

• Hard Glass (borosilicate)

• Sizes – BT56, BT37, BT28, ET18, E17, PAR38, T6, etc.

– Letter refers to bulb shape

– Number refers to bulb diameter in “eighths of an inch”

Base

• Provide electrical path from socket to stem lead wires

• Brass or Nickel plated brass

• Glass or ceramic insulator

Key Lamp Components (cont.)

BT56 ET18

ED17E17 PAR38 PAR30LN PAR20

ET23.5BT37 BT28

T6/G12

Outer Jacket Shapes

MH Lumen Maintenance

0

2,500

5,000

7,500

10,000

12,500

15,000

17,500

20,000

22,500

25,000

0 5000 10000 15000 20000

Operating Hours

Lu

men

s

Standard MH

Premium MH

High Pressure Sodium

Most efficient of the popular lamp types

Contain mostly sodium and small amount of mercury plus xenon gas

Used almost exclusively for outdoor lighting – roadway, security, flood lighting, façade, airport

Various types available – “ECO”, non-cycling, high CRI, standby

Characteristics of High Pressure Sodium Lamps

•Highest efficacy of popular lamp types – up to 140 lpw

•Arc tube of translucent alumina (ceramic) contains sodium, small amount of mercury, and xenon gas

•Light is “yellow-orange”

•CCT = 2100K; CRI ~ 22

•Up to 140,000 lumens

•Lamp cycles at end of life (non-cycling types available)

•“ECO” types with low mercury, lead-free designs

Dome Mount Supports

Base

Stem

Outer Jacket

Frame

Getter

Starting Aid

Alumina Arc Tube

Low Pressure Sodium Lamps

Highest efficacy light source: up to 200 lpw

Monochromatic yellow light @ 589nm

Used where color rendering is not of primary importance:

Roadway lighting, tunnel lighting, security lighting, lighting near observatories

HID Ballasts

Most HID ballasts are magnetic

Electronic types available for some lower wattage lamps, mainly 20W – 400W MH

Newer magnetic types (for pulse start MH) use a special starting component called an “ignitor”

Electronic ballasts have an integral ignitor

HPS magnetic ballasts have always used ignitors

Magnetic ballasts are available in a variety of types for outdoor use, remote mounting, and mounting inside of poles

Characteristics of HID Ballasts

Magnetic

•Large and heavy

•Fair to good lamp power regulation

•Available in myriad of types for many applications

Electronic

•Smaller and lighter than magnetic

•Can have very good power regulation

•Do not increase lamp efficiency (as in fluorescent)

•Not high frequency

•Can provide improved lumen maintenance and reduced color shift, therefore potentially longer life

•Not available in higher wattages; more expensive than magnetic types

The Light Emitting Diode (LED)

LED Light Sources

•Generically known as Solid State Lighting (SSL)

•Depending on type, can emit IR, UV, or light

•LEDs and luminaires are available from numerous manufacturers, not just the traditional lighting companies

•The lighting market for LEDs is still very small, but growing

•New product development more akin to electronics industry than to lighting industry

•Product life cycles are short (12 – 18 months)

LED Construction and Operation

•Consists of a multi-layer, semiconductor material

•N-type layer of material has excess electrons (negative charge)

•P-type layer has a deficiency of electrons, the absence of which are called “holes” (positive charge)

•The active layer is not a separately applied layer – it forms at the junction of the p and n material

•With the application of an external DC voltage, the electrons and holes combine at this active layer

•When an electron fills a “hole” at the active layer, it drops to a lower energy state; the energy it loses in doing so is given up in the form of a photon

LED Packages

•LED chips are packaged with various configurations

• Simple twin lead (original method)

• Flat package (SMD) with single LED

• Flat package with multiple LED chips

LED Packaging Considerations

•Optical

• Light extraction from the chip (key factor in determining efficacy)

• Total light output of the package

– Primary and secondary optical components

•Electrical

• Physical connection of lead wires to chip

• Power leads into the package

•Thermal

• Heat extraction from the p-n junction

• Heat transfer to an external heat sink

White Light from LEDs

• Since the introduction of the blue LED in the mid-90’s, white light from LED’s became possible

• Several ways to produce white light1. Mix the light from discrete red, green, and blue LEDs

2. Use a blue LED to excite a yellow phosphor coating

3. Use a UV or violet LED to excite a multi-component phosphor

• Easiest method from a cost and simplicity standpoint is #2 above.

• CCT, lumens, and CRI are fixed for #2 and #3.

• To dynamically adjust CCT, lumens, and CRI, discrete R, G, and B LEDs are necessary

Application Issues

LED life ratings

• Based on 70% lumen maintenance point, not mortality

• Different maintenance requirements for various applications

• IES LM-79 and LM-80 have been adopted to define LED life and lumen maintenance

Thermal design

• Proper heat sinking required to achieve rated life

• Auxiliary forced cooling may be required (air or water)

Optical performance

• Secondary optics can be selected for various beam spreads

Ambient conditions

• While an LED’s light output is not as temperature sensitive as fluorescent, high ambient temperatures must be taken into account when heat sinking

• Humidity and dirt conditions must also be considered

Other Light Sources

Cold Cathode (“Neon”)

• Special type of low pressure discharge using robust electrodes• Can be pure gas discharge or phosphor-coated with mercury discharge• Typically used in sign or linear decorative applications (check out the food

court at your shopping mall)

Electroluminescent

• Uses phosphors directly excited by an electric field• Typically used for instrument panel or cell phone keypad backlighting,

signage, or decorative effects

Organic Light Emitting Diode (OLED)

• Special type of LED using polymers (plastics) for the light emitting layer• Used in displays for cell phones, MP3 players, and now small video screens

Daylight

• Can be used to supplement or replace electric lighting• Needs to be integrated into the architectural and lighting design for buildings

to properly take advantage of it for energy savings

Module 2: Quiz Time!

Congratulations – you have concluded Module 2.

Now, it’s time for the quiz.

Good luck!