Lighting - Lamps 

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edisonBulbPatent
Electric Lamp Patent by Edison, 1880
Image Source: ourdocuments.gov
Lamps are the essential part of any luminaire. These are the light generating components. Since the advent of electrical lighting in the middle of the 19th century, multiple types of lamps have been developed. Over the years lamp technology continues to evolve offering increases in performance and efficiencies.

Lamp Types

Filament Lamps

Electricity heats a filament until it is incandescent (around 2800 K).

  • General Lighting Service Lamp, GLS - designed for general lighting service with tungsten filament surrounded by inert gas and enclosed in a glass bulb.
  • Tungsten-halogen, TH - use of halogen vapour allows a higher operating temperature and increased efficacy

Discharge Lamps

Ionisation of a gas (or metallic vapour), initially by the application of an high voltage pulse followed by charged particles colliding with atoms. This causes radiation to be given off.

  • Low pressure lamps - have relatively long distances between collisions allow charged particles to build up sufficient speed to cause excitation
  • High pressure lamps - an increase in the number of collisions (due to a denser arrangement of atoms) causes sufficient heat to raise the temperature of the gas
  • Fluorescence - low pressure mercury discharge produces ultra-violet radiation, converted to visible light by fluorescent or phosphor coating

Sarters (Ballasts)
Discharge lamps require starters to enable a high voltage to be applied to the lamp during starting , while limiting the current flowing once the gas has become ionised.  Possible starters include:

  • Resistance - can limit current flowing, not used due to large heat dissipation
  • Reactance - can limit current flowing, commonly used
  • Capacitance - can limit current flowing, only used on rare occasions
  • Ignitor - generates series of high voltage pulses,  staring of lamps at voltages higher than mains
  • Reactance autotransformer - provides higher than mains stating voltage, limits operation current
  • Glow starter - closes or opens the pre-heating circuit of a fluorescent tube
  • Electronic starter - device for fluorescent tubes to provide necessary pre-heating of the electrodes

Modern Technology

Recent drives to create more efficient and environmentally friendly lamp technology has see much research and development in the fields of LED and Induction Lamps.

  • LED (Light Emitting Diode) - electric current flowing through a semi-conductor junction cause light to be emitted.
  • Induction Lamp a high frequency electromagnetic field is injected is used to excite mercury, producing UV radiation and phosphor coating converts to visible light

Summary of Lamp Characteristics



Lamp


Description

Watts
W

Efficacy
lm W-1
Life (hours) 
1000's
Colour
Typical
Application
CCT RG Class
Filament
GLS

General lighting service

25 to 1000

8 to 18

1 to 2

2800

1A Warm Home

TH

Tungsten halogen

25 to 1500

18 to 24

2 to 4

2900 1A Warm Display
Tubular Fluorescent

T5

15 mm diameter 4 to 80 37 to 94 1 to 4 2800 to 6500 1A,1B,2,3 All

Factory, office & shops

T8 26 mm diameter 18 to 70 75 to 93 1 to 1.5 As above As above All  
T12 38 mm diameter       As above As above All  
Sodium

SOX

Low pressure

10 to 135

100 to 200

6 to 20

None     Roads

SON

High pressure

50 to 1000

70 to 130

6 to 24

2000 to 2200 2,4 Warm Industry
Mercury
MBF High pressure

50 to 1500

35 to 55

5 to 24

3800 3 Intermediate Industry
MBTF High pressure blended (MBF+filament)

50 to 1500

           
Metal halide
MBI High pressure discharge

70 to 1000

65 to 85

5 to 12

5200 2 Intermediate Industry, commerce

If your looking for a good (more detailed) comparison of technical parameters across all lamps, the Thorn Technical Handbook is a good resource (freely available online)

Typical Currents & Recommended Fuse/MCB Ratings

  Current (A) Fuse/MCB (A) for No.Lamps
Watt μF Start Run 1 2 3 4 5 6

SOX

18

     

4

4

4

4

4

4

SOX

35

     

4

4

4

4

4

4

SOX

55

     

4

4

4

4

4

4

SOX

90

     

4

4

4

4

6

6

SOX

135

     

4

10

10

16

20

25

SON

50

 

0.35

0.3

4

4

4

4

4

4

SON

70

 

0.55

0.4

4

4

4

6

6

10

SON

100

 

0.7

0.52

4

4

4

6

10

10

SON

150

 

0.7

0.8

4

6

10

10

16

16

SON

250

 

1.5

1.3

10

16

16

20

20

20

SON

400

 

3.0

2.15

16

20

20

25

25

32

SON

1000

 

6.0

5.4

20

25

32

40

50

63

MBF

50

6

0.32

0.3

4

4

4

4

4

4

MBF

80

8

0.5

0.4

4

4

4

4

6

6

MBF

125

8

1.1

0.7

4

4

6

10

10

10

MBF

250

13

2.2

1.33

10

16

16

20

20

20

MBF

400

20

4.0

2.2

16

20

20

25

25

25

MBF

700

20

6.5

3.5

16

20

25

32

32

40

MBF

1000

50

9.0

5.5

20

25

32

40

50

63

MBI

150

20

0.76

0.76

4

6

10

10

16

16

MBI

250

30

1.5

1.3

10

16

16

20

20

20

MBI

400

25

3.5

2.0

16

20

20

25

25

25



Steven McFadyen's avatar Steven McFadyen

Steven has over twenty five years experience working on some of the largest construction projects. He has a deep technical understanding of electrical engineering and is keen to share this knowledge. About the author

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