DATA BANK
 
 
 
 

Figure 8.7. Types of halogen lamps.

LLLLinear halogen lamps have a slim tubular bulb and recessed single-contact lamp caps (R7s), one at each end of the lamp. Wattages range from 100 to 2000 watts./p>

Figure 8.8. Linear Halogen Lamp./p> p>LLinear halogen lamps are also available as Halogen-]R lamps with the bulb coated with a patented GE POW-IR film. This is an infra-red reflecting material that directs heat back on to the filament and reduces the amount of electrical energy required to produce a given level of light output. See Figure 8.9. Available in 225 and 375W ratings.

Figure 8.9. Halogen-IR linear lamp./p> p>Most mains voltage single-ended halogen lamps also have an outer bulb. There are three main shapes:

  • HaloGlobe
  • HaloBTT
  • Halo T

HHHaloGlobe and HaloBTT can be operated in any position, but Halo T is horizontal burning only. These lamps can be used in open luminaires.

Figure 8.10. Single-ended halogen lamps./p> p>Halogen PAR lamps are lamps within lamps. A small halogen capsule is mounted and sealed inside a PAR bulb as shown in Figure 8.11, and thus the advantages of halogen efficacy and long life are combined with beam control from the PAR shape.

Precise ConstantColor Lamps
Precise lamps as shown in Figure 8.12 are very small. They are available in two sizes:

  • 35mm reflector - called MR 11
  • 50mm reflector - called MR 16.

The lamps are rated at 12 volts and need a transformer to reduce the normal 240V to 12V. Wattages range from 12 to 75W and the range of beam spreads is from 7 to 55 degrees.

TThe lamp caps are all 2 pin (GU4 for MR 11 and GU5.3 for MR 16). They are available as open reflectors or with a front cover glass. The life of MR11 lamps is 3500 hours (2000 hours for 12W). The life of MR16 lamps is 4000 hours for all ratings except 50W which has 5000 hours life. The open reflector version should be used in enclosed luminaires.

Figure 8.12. Precise ConstantColor lamps./p>

GE's exclusive ConstantColor dichroic coating provides consistent colour quality and long life.

  • Consistent white light.
  • No discoloration at the beam edges.
  • No discoloration of the reflector.
  • No fringe colours.
  • No lumen loss due to coating discoloration.
  • 50W versions have 6000 hour life.
  • Cool beam with over 60% of IR radiation transmitted backwards through the reflector.
Special Lamp Types
Described above are the main types of halogen lamps used for general lighting. There is a wide range of halogen lamps for special applications such as auto lamps, projector lamps, heating lamps, and stage/studio lamps.

Additional Advantages of Halogen Lamps
Halogen lamps offer a number of economic and quality advantages:

  • Provide excellent colour rendering.
  • Light is whiter than that of conventional incandescent lamps.
  • Continuous spectrum with particular emphasis on warm colours.
  • Unmatched in precise light control from small, lightweight luminaires.
  • Small luminaires because of small lamp size and no ballast required. (Low volt versions do require a transformer.)
  • Luminaires are easy to install.
  • Halogen lamps deliver full light output at the flick of a switch.
  • No warm-up required.
  • Simple dimming control is possible.

Halogen Lamp Applications
Halogen lamps are ideal for a wide range of applications from airports to TV studios as can be seen from the following list:

    Airfields
    Radiant Heating
    Department Stores
    Slide Projectors
    Security Lighting
    Vehicle Lamps
    Display Cases
    Theatres
    Supermarkets
    Shop Windows
    Dentistry
    Traffic Signals
    Garden Lighting
    Lighthouses
    TV and Film Studios
    Operating Theatres
     

Dental spotlights  are typical of optical devices and instruments that use halogen lamps. Some use low voltage lamps with smaller filaments to approximate a point source of light. Low voltage lamps have higher lamp efficacy and better beam control. However, low voltage lamps require a transformer.

Downlights often use single-ended capsule lamps or low voltage reflectors. Small unobtrusive luminaires are possible because of the compact lamp proportions. See Figure 8.14. Downlighting is found in offices, stores, lobbies, restaurants, theatres, hotels and homes.

 


ANSI Specification
This is a three letter random code from American National Standards Institute e.g. EZX. It describes the lamp exactly. If a characteristic of the lamp is significantly changed, such as beam angle or wattage, it is a new lamp and is given a different ANSI code.

LIF Reference
This is a single letter followed by numbers from Lighting Industry Federation e.g.

  • Al/ projector lamps
     
  • K/ floodlighting lamps
     
  • T/ theatre lamps
     
  • M/ miscellaneous lamps

It describes the lamp exactly. If a characteristic of the lamp is significantly changed, such as beam angle or wattage, it is a new lamp and is given a different LIF code.

The LIF is the (British) Lighting Industry Federation.
Both these reference systems are used industry-wide so the customer has a clear indication of compatibility between manufacturers products.

Other order codes are similar to incandescent lamps but the information sequence changes, e.g. G95/150/ES/230.W is a 230V 150W HaloGlobe with White bulb and ES cap.

 

FLUORESCENT LAMPS
There are six different categories of fluorescent lamps:
1. Standard Bi-pin (T8 and Tl2)
2. Miniature (T5)
3. Mod-U-Line
4. Circline
55. The Biax range - Biax, Biax D, T, Q and 2D



Figure 2.15. Fluorescent lamp categories.br>
Fluorescent Tube Diameter
This is measured in eighths of an inch and has the prefix "T" so T8 is a tube of one inch in diameter. Customers may quote metric measurements. 16mm is T5, 26mm is T8 and 38mm is T12.

Apart from the standard types mentioned above there are special types from America, some of which are imported into Europe:

  • Watt-Miser
  • Slimline
  • High Output
  • Powergroove
  • Tl0

These usually require non-European standard control gear and so demand is limited to equipment imported from North America with lighting already built in. A significant proportion of these lamps is not available direct from GE in Europe.

 

Fluorescent Lamp Caps
FFor the straight tubes there are just two caps for the three lamp diameters.



Figure 2.16. Fluorescent lamp caps.br>
Note that the pin spacing is the same for T8 and Tl2 lamps so in most cases lamps of the same length are interchangeable. Some modern luminaires may not accept T12 lamps if the lampholders are designed to position a T8 lamp very close to the luminaire body or louvre. Old luminaires may also be incompatible electrically.

Other fluorescent lamp caps include:

  • Single pin - used on Slimline lamps (not interchangeable with the European TLX lamp)
     
  • Four pin - used on Circline, Biax and Biax 2D
     
  • TTwo pin - used on Biax and Biax 2D


Figure 2.17. Other fluorescent lamp caps.br>
Wattage Rating
Fluorescent lamps are rated in watts much the same as incandescent lamps. The standard fluorescent range is from 4 to 125W and is a more limited range than other lamp types.

Voltage Rating
Fluorescent lamps do NOT have a voltage rating. Each fluorescent luminaire contains a ballast that provides the correct voltage to the lamp for the connected supply voltage.

Lamp Shape and unlit appearance.
All fluorescent lamps have a smooth tubular shape with an internal phosphor coating. Blacklight Ultra Violet lamps are made of Woods glass and have an almost black appearance when not operating. Gold or Radar Red tubes (both obsolete) have additional filters so look Yellow or Red even when not operating. All other tube colours look the same white colour until the lamp is switched on.

 

Lamp Dimensions
A fluorescent lamp has two important dimensions:

  • Tube diameter
  • Overall length

IIn Europe the dimensions are measured in millimetres but the "T" reference is commonly used. When tube diameter is part of the order code, eighths of an inch are used, but for most lamps the diameter is obvious from the wattage.



Figure 2.18. Fluorescent tube dimensions./strong>

Lamp Finishes Fluorescent lamp finishes consist primarily of different phosphor coatings which cover a broad range of colours. There are four main families of "White" fluorescent lamps.
Standard Colours
These are older types of phosphor which have lower efficacy, poorer lumen maintenance and worse colour rendering. They should only be used to match existing installed lamps and where lamp cost is more important than efficiency or quality.

Because of the language complication of describing the colours of these lamps there is a two digit reference used in Europe, but note the numbers are NOT an indicator of any performance characteristic.

Initial Lumens
The light output claim for fluorescent lamps is described as initial lumens and is measured after 100 hours burning, which allows new lamps to stabilise. Light output is measured at 25 degrees Celsius in accordance with IEC 81 and 901. The new long T5 lamps are measured at 35 degrees Celsius.
 

Lamp Life
The life of a fluorescent lamp varies with:
  • The number of times the lamp is started.
  • How the lamp is started.
  • How it is operated after starting.

The longer the time of operation per start, the longer the lamp life. Standard rated average life assumes 3 hours operation per start.

Fluorescent Lamp Parts
Basically, a fluorescent lamp is made up of five components. See Figure 5.1.
  1. GLASS TUBE, coated on the inside with fluorescent powders called PHOSPHORS.
  2. Two ELECTRODES (or cathodes) coated with EMITTER, supported by a glass mount structure, and sealed at the ends of the tube.
  3. FILLING GAS - usually a low pressure of Argon or Krypton/Argon mixture.
  4. Small amount of MERCURY (less than 20 mg), which vaporises during the lamp operation.
  5. LLAMP CAP cemented to each end of the tube to connect the lamp to the lighting circuit.



Figure 5.1.br>
Fluorescent Lamp Operation
When the circuit is energised, electricity heats the cathodes. See Figure 5.2. The cathodes are coated with material which, when heated, emits electrons. The electrons establish an electric arc between the cathodes at opposite ends of the tube. The electrons collide with the mercury atoms, causing mercury to emit invisible ultra-violet radiation. The ultra-violet is absorbed by the phosphor coating on the tube and re-radiated as visible light.

& 

Figure 5.2. Principles of fluorescent lamp operation./strong>

Fluorescent Lamp Shapes
Fluorescent lamps have a limited range of shapes. Most common is the straight tube in various diameters. See figure 5.3. The diameter may be quoted in mm, but the universal term is "T" for tube followed by the diameter in eighths of an inch e.g. 26mm is T8. Most T12 lamps are now being replaced by more energy efficient T8 lamps of the same length but reduced power.

& 



Figure 5.3. Fluorescent tube diameters./strong>

U-shaped fluorescent tubes offer an alternative configuration, being shorter and with the lamp cap(s) at one end. See Figure 5.4.. Mod-U-Line tubes can fit into 600 mm x 600 mm ceiling luminaire, compared with 600 mm x 1200 mm luminaire for straight tubes. The biaxial shape has a single lamp cap with either two or four pins - GE trademark BIAX. More information on these lamps is given in the Compact Fluorescent Lamp section.



Figure 5.4. U-shape fluorescent lamps./strong>

Circular fluorescent lamps give another option. See Figure 5.5 . These have a four pin cap and are available in three different diameters.



Figure 5.5. Circline range.br>
Fluorescent Lamp Caps
There are three different types of lamp cap:
  • Single pin
  • Bi-pin
  • Four pin

Bi-pin is the most common and for straight tubes there are just two versions. See FFigure 5.6.



Figure 5.6. Bi-pin lamp caps./b>

Single contact caps are used for Slimline tubes which have a special starting circuit. Four pin caps are used on Mod-U-Line and Circline lamps.

& 



 

Figure 5.7. Other fluorescent lamp caps./strong>

Fluorescent lamp design is called HOT CATHODE, and requires a second or so before the lamp lights.  To provide the initial warm-up there is a device called a STARTER, which first connects the cathodes in series to allow preheating, and then switches the voltage across the two electrodes. The most common form of Starter is a small cylindrical component containing a glow switch.

All hot cathode lamps have bi-pin or four-pin caps.

Instant start circuits used to be a popular way to give quicker starting with no initial flickering. However, electronic starting methods are now replacing such control gear because they are more efficient and incorporate additional safety features.

The SLIMLINE lamp does not preheat the cathodes and requires special control gear from America, which has no starter. SLIMLINE has single pin caps. SLIMLINE lamps cannot be used on starter or instant start circuits.

Fluorescent Lamp Circuit Operation

Figure 5.8 sshows the basic fluorescent lamp circuit. The circuit must contain a ballast to limit the current and a starter to provide the pre-heat conditions. Initially the starter switch closes so the two cathodes are connected in series. Current flows and the cathodes heat up emitting electrons. After a short time the starter switch opens so voltage is applied across the tube. If sufficient electrons are available an arc is struck and the starter plays no further part until the next starting operation. If there are insufficient electrons, the tube will flicker, fail to start, and the starter will repeat the heating of the cathodes. The ballast limits the current to a safe and appropriate level for the power of lamp. Without the ballast, the current would increase to a high level and the lamp would destroy itself.



Figure 5.8. Fluorescent lamp circuit.br>
 

Operating Characteristics
Five operating characteristics of fluorescent lamps are:

  1. EFFICACY - defines light output per unit of power input.
  2. LUMEN MAINTENANCE - defines the decreasing light output as the lamp ages.
  3. MORTALITY - defines average lamp life expectancy.
  4. COLOUR RENDERING - defines how fluorescent lamps display the colours of objects.
  5. ENVIRONMENTAL CONSIDERATIONS - defines how fluorescent lamps respond to extremes in their operating conditions.

FFluorescent Lamp Efficacy

 

Lamp Efficacy = Lumens (light output)
                       Watts (power consumed)

                    = Lumens per Watt (L/W)  

Fluorescent lamp efficacy is 3-7 times higher than incandescent:

  • 100W gls 13.5 L/W
  • 1500mm 58W 47-93 L/W

Fluorescent lamp efficacy is dependent upon the lamp colour, lamp length, ambient temperature, and frequency of the supply voltage.

Lamp efficacy varies by lamp colour:

  • Polylux XL 840 gives 93 L/W
  • Polylux Deluxe 940 gives 65 L/W
  • Cool White gives 81 L/W Polylux XL provides the best L/W and operating efficiency.

Both lamp length and current affect efficacy:

 

Polylux XL 835      
2400mm 100W     94 L/W
1800mm 70W     94 L/W
1500mm 58W     93 L/W
1200mm 36W     96 L/W
600mm 18W     81 L/W


Lamp efficacy and output is affected by extremes in ambient temperature. See Figure 5.9. Fluorescent lamps are relatively sensitive to ambient temperature because they are low pressure lamps. Optimum lamp operating temperature is 5-25 degrees Celsius. Above this limit the efficacy falls by approx. 1 % for every degree rise. Below this limit the efficacy fails by approx. 5% for every degree fall. Fluorescent lamps should be protected from draughts that can reduce lamp wall temperature and light output.

& 



Figure 5.9. Lamp efficacy and ambient temperature



Figure 5.10 shows how the frequency of supply voltage affects light output.br>
Frequencies of 30kHz improve light output by up to 10%. This is why the use of high frequency electronic ballasts is becoming popular. Additional benefits are the high frequency eliminates any irritating flicker, is better starting, and the ballasts are lighter. Different size and shape configurations are easy to arrange with the electronic components. These features are of particular benefit to aircraft, marine and emergency lighting applications.

Lumen Maintenance
Light output decreases as the fluorescent lamp ages.
Phosphors deteriorate and produce less light.
Blackening at the ends of the lamp blocks light.
Light output decreases even if the lamps do not burn out. See FFigure 5.11.



Figure 5.11. Lumen maintenance over time./strong>

Mean lumens is an American measure taken at 40% of rated lamp life. In UK lighting levels are based upon maintained illumination and it is necessary to determine the minimum lighting level in the installation when replacement of lamps is due, taking into account all possible reasons for deterioration. This is not a set figure and will vary according to the operating conditions at each location.

 

Fluorescent Lamp Mortality

Lamp mortality defines how long the average lamp is expected to last. It is expressed as RATED AVERAGE LIFE in hours of operation. See FFigure 5.12.



Figure 5.12. Lamp mortality curve./b>

Average rated lamp life is when 50% of the large sample batch tested have failed and 50% are still operational. This is different to the time when the lamps are replaced, which is usually well before 50% failures occur from a batch.
Several factors affect fluorescent lamp life. Longer burning hours per start will extend lamp life. Lamp life is shortened by improper lamp current, improper voltage to the ballast, or improper cathode heating.
Average rated lamp life is based upon 3 hours per start for all fluorescent lamps. See Figure 5.13. Increasing burning hours per start from 3 to 12 hours increases lamp life, by 50%.



Figure 5.13. Typical life increase vs. burning hours per startbr>
Overvoltage to the ballast will cause high tube current shortens lamp and ballast life. It also causes preheat lamps to start like instant start lamps - shortens lamp life.

Undervoltage to the ballast causes low tube current - makes lamps flicker, causes uncertain starting and reduces light output. Undervoltage to the ballast can cause preheat starters to recycle - shortens starter and lamp life.

Colour Rendering
Colour rendering defines how the light from the lamp affects the colours of objects being illuminated. Fluorescent lamp colour depends upon the phosphors within the lamp. Fluorescent lamps offer a range of colour rendering performance, but will not match incandescent lamps.
& 



Figure 5.14. Colour rendering.br>
Fluorescent lighting is often considered a "neutral" or "cool" appearance when compared with incandescent light. Special GE fluorescent lamps provide specific colours for plants, aquaria,- photocopiers, and germicidal applications.

Environmental Considerations
Fluorescent lamps are affected by extremes in ambient temperature. They operate best in the range 5-25 (35 for High Output T5) degrees Celsius. Below this there is a rapid drop in light output and difficulty in starting.
High humidity causes electrical leakage along the lamp surface - lowers the starting voltage provided by the ballast. Lamps are pre-coated with silicone to break up the moisture film and prevent such leakage.

Fluorescent Lamp Advantages
  1. Fluorescent lamps are 3-7 times more efficient than incandescent lamps.
  2. Power consumption for equal light output is much less than for an incandescent lamp.
  3. Rated lamp life is between 5,000 and 18,000 hours, depending on style, approximately five to eighteen times longer than typical incandescent lamp life.
  4. Lamps can be selected for desired colour rendering purpose e.g. aquaria.
  5. Available with wattage ratings from 4 to 125W. (There are 215W High Output and Powergroove lamps but these will not operate on conventional European control gear.)
  6. Low surface brightness provides better visual comfort and diffused lighting.
  7. Optional dimmable ballasts are available. Lamp colour does not significantly change when dimmed. Power consumed is proportional to light output.

Fluorescent Lamp Disadvantages

  1. Variations in supply voltage affect lamp light output and starting.
  2. Required external equipment (ballast) consumes energy, adds to equipment cost. For retro- fits, establishes lamp size and wattages that can be used.
  3. Lamp frequency flicker can cause discomfort to some people.
  4. Operation on a range of supply voltages requires different control gear components or more expensive tapped ballasts.
  5. Ballasts may produce irritating 100HZ humming sound - only reliable solution is to replace ballast.
  6. Lamps are large for the amount of light produced - HID and incandescent lamps are much more compact.
  7. Radio frequency interference from lamps may disturb communications equipment at close range. Note there are new EMC (Electro Magnetic Compatibility) Regulations due to come into force for the EU.
  8. Distracting lamp flashing can occur with a glow starter attempting to strike a failed lamp.
  9. Stroboscopic effects can make rotating machinery appear stationary which could be a potentially dangerous situation.

 
Compact Fluorescent Lamps

Overview
Compact fluorescent lamps resulted from research into energy saving lighting. The goal was to develop smaller, more efficient light sources with greater lumen output per watt. One solution was to re-design the fluorescent lamp and its cap. Two basic designs have emerged. See Figure 6.1.. The internal construction and function of all variants is very similar to linear (straight) fluorescent lamps.

  1. Biaxial: the tube is reduced to half its length with two 90 degree bends. This shape is similar to Mod-U-Line but narrower. BIAX is the GE trade name for the biaxial design of fluorescent lamp.
  2. SSquare planar: the tube is made into a square shape with the lamp cap in the centre. This is a more complex shape with both 90 and 180 degree bends. This shape is called 2D (two dimensional) and is a unique GE product. Both types bring the ends of the tube together in one lamp cap.

Figure 6.1. Compact fluorescent lamps./p>

There are seven CFL product lines:

 

STYLE WATTAGE RANGE
BIAX S 5-11W
BIAX D 10-26W
BIAX T 13-32W
BIAX Q 42W
BIAX L 18-55W
BIAX2D 10-55W
GLOBE 111-20W

Figure 6.2. Complete CFL range. /font>

Biax S Lamps Low wattage lamps were the first GE Biax introductions, and are available with either two or four pin caps. Argon is the tube filling gas. See Figure 6.3.

Figure 6.3./p>

The two pin versions have an internal starter built into the cap and are not dimmable. The four pin versions require external starting and are suitable for dimming and emergency lighting. Both versions require a separate ballast as for a conventional fluorescent lamp. Biax S lamps have a rated average life of 10,000 hours based upon 3 hours per start. All compact fluorescent lamps feature Polylux phosphors so have excellent colour rendering (Ra 82). The colours range from 2700K to 4000K.

Primary applications for Biax S (and Biax D, Biax T, Biax Q, and 2D) are to replace less efficient incandescent lamps in:

  • downlights
  • entrance and security lighting
  • task lighting
  • wall washing.

Primary applications for Biax L lamps are to replace linear fluorescent tube and low wattage HID lamps in:

  • uplights
  • recessed louvered ceiling luminaires
  • accent lighting.

Four primary advantages of Biax S lamps:

  1. Energy saving: much higher efficacy than incandescent lamps.
  2. Long life.
  3. Choice of colour temperature.
  4. Design flexibility: more light with less unwanted heat.

Biax L Lamps
All are four pin and are dimmable.

They use remote control gear which can be either a conventional ballast and starter or the high frequency electronic type. High frequency ballasts must be used with the 40W and 55W lamps Rated lamp life is 10,000 hours based upon 3 hours per start.

 
& 

Figure 6.4. Biax L lamp./p>

There are many applications for Biax L lamps:

  • Task lighting.
  • Security lighting.
  • Uplighting.
  • General lighting in recessed and asymmetric luminaires.

Four Primary advantages of Biax L lamps.

  1. Significant energy saving over incandescent lamps.
  2. Excellent colour rendering.
  3. Design flexibility - more light from a smaller size of lamp.
  4. Higher wattage versions can be used as alternatives to low wattage discharge lamps.

Double (D), Triple (T) and Quad (Q) Biax Lamps
These are more complex versions of the Biax S and L configuration, with either two or three 180 degree bends applied to one tube.

TThe main advantage is the further reduction in size for the same power. In Figure 6.5 Biax S, Double Biax, Biax T and Biax Q lamps of the same wattage rating are compared. The highest wattage 2D, T and Q lamps can also be used where low wattage metal halide or mercury lamps may have been specified before.

Figure 6.5. Size comparison./p>

CFL Adaptor Systems
CFL Adaptor systems modify the standard Compact Fluorescent lamp for use in standard incandescent sockets. The lamp simply plugs into the adaptor and complete assembly is inserted into the incandescent socket (E27 or B22).

There are also adaptors where the lamp is not replaceable. In some situation this form can be mofe convenient for maintenance.

A 15W Double Biax, for example, can replace a standard 60W gls lamp and provide the same amount of light. Lighting energy costs are reduced by over 70%.

Electronic adaptors improve lamp efficacy, are lighter in weight and operate at high frequency.

Electronic Biax SA and 2D adaptors have connectors so the compact fluorescent lamp can be replaced and the adaptor reused. Adaptor life is approximately 32,000 hours.

Life / economics
To maximise the power saving and long life features of CFL lamps when used to replace existing gls bulbs, they are best used where the lamp will be on for relatively long periods. Inappropriate use, such as with domestic presence detectors (P.I.R.'s) or similar equipment, may shorten the life significantly and additional power savings will be minimal.
HIGH INTENSITY DISCHARGE (HID) LAMPS
This family of lamps includes:
  • high pressure sodium
  • metal halide
  • hhigh pressure mercury





Figure 2.22. High intensity discharge lamps.br>
Low Pressure Sodium Lamps
Low pressure sodium lamps, although similar to high pressure sodium lamps, are not really HID lamps, and are more closely related to fluorescent tubes. They are manufactured under the SOX and SOX-E product names. Because of their monochromatic yellow colour their use is mainly restricted to roadway lighting. However the narrow customer base should not be underestimated, as they are a valuable contribution to discharge lamp sales.
 

High Intensity Discharge Lamps

Operating Principles

High Intensity Discharge" is often shortened to "HID" or "Discharge". HID lamps give out light from an intense electrical arc or “discharge” between two electrodes. See Figure 9.1.

TThe process is similar to the fluorescent lamp, except that the light comes from the arc itself, and not from the phosphor coating on the tube wall. Some discharge lamps do have phosphor coated bulbs but this is only to provide supplementary colour and / or increase the apparent size of the source to reduce glare.

Figure 9.1. HID lamp operation./p>

Figure 9.2 shows the basic parts of Kolorlux and Metal Halide lamps:

  1. Outer bulb of heat resistant glass; small amount of nitrogen fill gas at a very low pressure.
  2. Quartz arc tube; fill gas of argon; small amount of mercury and other metals, depending upon the lamp type.
  3. Starting electrode (not for some metal halide lamps).
  4. Two main electrodes and supporting structure.
  5. CCap to connect lamp to the power circuit.

Figure 9.2. Mercury and Metal Halide lamp construction. !----- CONTENT ------------->

Starting and operating principles of Kolorlux and Multi-Vapor lamps are shown in Figure 9.3:
  • When the circuit is energised, a small arc forms between the starting electrode and adjacent main electrode.
  • The arc ionises the fill gas and metallic vapour.
  • When enough ions are present in the arc tube, the main arc strikes between the two main electrodes (resistance drops sufficiently).
  • Current to starting electrode stops as the resistance is higher than that between the main electrodes.
  • Main arc radiates intense light.

HHID lamps require several minutes to "warm-up" and reach stable operation. During this period the heat from the arc vaporises the metal(s) in the arc tube and the vapour pressure increases. If switched off, the lamp requires several minutes cooling before the arc can re-strike.

Figure 9.3. Kolorlux and Multi-Vapor lamps starting operation./p>

Note that metal halide lamps without a starting electrode start in the same manner as Lucalox lamps described later in this section. Like fluorescent lamps, HID lamps require an external ballast. This supplies sufficient starting current and voltage to allow the arc to strike and to stabilise after warm-up. In stable operation the ballast limits the lamp current to control the arc discharge and to prevent the lamp from self-destructing. The ballast is specific to each lamp type and power rating and is for a single supply voltage unless provided with input connections (taps) to select an alternative voltage.

Types of HID Lamps
There are four main ranges of GE HID lamps:

  • Kolorlux mercury lamps
  • Multi-Vapor and Kolorarc metal halide lamps
  • Lucalox high pressure sodium lamps
  • SOX low pressure sodium lamps

The first three have similar general construction and operating principles. SOX lamps are more akin to fluorescent tubes only without the phosphor coating and using sodium in place of mercury.

Kolorlux Lamps

TThe Kolorlux lamp (high pressure Mercury), shown in Figure 9.4, was one of the first HID lamp types to appear on the market in 1930s. The outer bulb stabilises and maintains the necessary high temperature around the arc tube and also absorbs the potentially hazardous UV radiation coming from the arc. Nitrogen gas within the outer bulb protects the metal parts from oxidation. The bulb is phosphor coated to generate some red light that is added to the light from the arc tube, improving the colour rendering and appearance of the lamp. The light direct from the arc is mainly blue and green.

Figure 9.4. Kolorlux lamp construction./p>

IInside the arc tube the starting gas is Argon. See Figure 9.5. Mercury ions support the arc after the lamp starts. The main electrodes are double layers of tungsten wire with rare earth oxides for long life and good lumen maintenance. The starting resistor limits the current to a low value for starting. After the lamp starts the current bypasses the resistor and starting electrode as soon as the resistance between the main electrodes fails to below that of the starting resistor.

Figure 9.5. Kolorlux lamp starting system./p>

Kolorlux lamps offer distinct advantages over incandescent lamps - see Figure 9.6.

  • High lumen output per watt
  • Cool colour appearance
  • Long life
  • Low operating cost
MERCURY

Figure 9.6. Comparison of mercury and incandescent lamps./p>

Example:
A 250W Kolorlux Deluxe lamp uses 45% less energy and produces 59% more light than a 500W incandescent lamp. The life of the mercury lamp is twenty times longer (20,000 hours).

MeMercury lamps are available with elliptical and reflector bulb shapes; the wattage range is from 50W to1000W. See Figure 9.7. Most popular are 125W to 400W lamps for general lighting.

Figure 9.7. Typical mercury lamps.p>

Kolorlux lamps are widely used for:

  • Lighting residential streets
  • Industrial interior and exterior situations
  • Amenity lighting

The reflector lamps are used in dirty atmospheres where conventional luminaries reflectors would soon deteriorate.
Multi-Vapor Lamps

FiFigure 9.8 shows how Multi-Vapor metal halide lamps are similar to mercury lamps. The chief difference is that the arc tube contains metal halides in addition to mercury. The outer bulb is of the same materials and functions as in the mercury lamp. Both clear and phosphor coated versions are available. The main electrodes are similar to those of mercury lamps except there is no emission coating and they are larger. The starting electrode is the same except there is a bimetallic switch that shorts the starter circuit to the main electrode after the lamp starts. The arc tube is slightly smaller than in the mercury lamp. The ends have a white reflective coating to control the arc temperature and metal vaporisation. Also the ends are moulded to a precise parabolic shape. The arc tube support is "frameless" to prevent magnetic interference with the metal halides. Most Multi-Vapor lamps require special metal halide ballasts, and compatibility between lamp and control gear should always be checked.

Figure 9.8. Multi-Vapor lamp construction.p>

MuMulti-Vapor lamps operate on the same general principles as mercury lamps. See Figure 9.9. The addition of metal halides into the arc tube affects the light output and improves the colour characteristics. The metal halides vaporise into halogen and metal in the central core of the arc (hottest area). The additional metals radiate more light than mercury and at desirable colour wave-lengths. It is the combination of several metals that produces white light and the number and proportion of the metallic constituents can vary this colour. As the metals and halogen move out of the central arc towards the tube walls they recombine at the cooler temperature. This halogen cycle repeats.

Figure 9.9. Multi-Vapor lamp operation. ----- CONTENT ------------->

Multi-Vapor lamps offer greater light output than comparable mercury lamps, typically 50% to 100% more lumens per watt. Consequently less wattage is required for a given lighting level and less power is consumed.

MuMulti-Vapor lamps come from USA and the different supply voltage to Europe has caused different types of control gear to be developed. Multi-Vapor lamps must be operated with the correct American type control gear and not with the standard types of Metal Halide gear used in Europe. One or two European gear manufacturers do produce suitable ballasts for American lamp designs. Multi-Vapor lamps are not suitable for operation with European specification Mercury ballasts. Multi-Vapor lamps provide good colour uniformity from lamp to lamp and better colour rendering than Kolorlux lamps. See Figure 9.10. They are visually cooler than Kolorlux lamps and closest to Cool White fluorescent tubes. The phosphor coated versions offer even better colour rendering.

Figure 9.10. Multi-Vapor colour characteristics.p>

Multi-Vapor lamps are sensitive to burning position with vertical (± ±l5°) preferred for most. See Figure 9.11.

With the standard cylindrical arc tube:

  • Horizontal burning creates a hot upper wall as the arc bows upwards.
  • Hot wall interferes with the halogen cycle reducing light output. Also the arc tube can be weakened.

SpSpecial "configured" arc tubes follow the bow of the arc and permit horizontal burning. Always check burning position when ordering as there are separate products for horizontal and vertical positions. Correct axial orientation of the lamp is ensured by the use of a “pegged” cap. Standard Edison screw sockets cannot be used.

Figure 9.11. Multi-Vapor burning position. ----- CONTENT ------------->

Most Multi-Vapor lamps are available from 175W to 1000W. Rated life is from 6,000 to 20,000 hours, depending on model and burning position. See Table 1.

Table 1. Multi-Vapor wattage and rated life.

 

Wattage     Rated Average Life
  Vertical     Horizontal    
175 10,000 6,000
250 10,000 10,000
400 20,000 15,000
1000 12,000 12,000

BuBulb shapes are mainly elliptical but some are bulged-tubular.

Figure 9.12. Multi-Vapor bulb shapes.p>

European Metal Halide Lamps
Kolorarc, Arcstream and Sportlight are general groupings of metal halide lamps designed in Europe (excepting MXR) and suitable for normal European control gear. These lamps do not use a starting electrode but are started by an ignitor (explained in the Lucalox section).

Kolorarc
Kolorarc lamps are rated at 400W and have tubular, clear elliptical and phosphor coated bulbs. The burning positions are restricted and this should be checked with each order. Lamp life varies from 10,000 hours to 14,000 hours.

Kolorarc lamps have CCTs ranging from 4000 to 6000K and the colour rendering Ra from 65 to 90. All lamps have KRC as the description prefix.

Arcstream lamps
The GE Arcstream range includes all Metal Halide lamps, from 70 to 400 watts rating, which will run on compliant High Pressure Sodium ignitor / ballast control gear. Recent developments include the increasing use of UV control quartz on the compact lamps to limit the amount of UV emission.

The Arcstream Constant Colour CMH lamps incorporate new arc tube technology, which, rather than Quartz, uses the same material for the arc tube as High Pressure Sodium lamps.. This improves colour stability dramatically and improves life. All style descriptions are prefixed with ARC with the exception of CMH and the 100 Watt MXR lamp.

Arcstream Single Ended Metal Halide Lamps
70W and 150W compact single-ended tubular metal halide lamps have quartz outer bulbs that reduce lamp size for use with compact spotlight luminaires. They must be used in enclosed luminaires with protection against UV radiation from the lamp. Rendering average is Ra80 and there is a choice of colour temperature 3000K or 4000K. The 250W and 400W tubular E40 capped lamps, can also be retro fitted into existing High Pressure Sodium luminaires, which must be enclosed. Colours available are 4200K, Ra70 and 6000K, Ra 90.

Elliptical 250W clear and diffuse lamps run on 250W Sodium ballasts but ignitor compatibility must be checked.

Arcstream Double-Ended Metal Halide Lamps
ThThese are also high performance lamps for display lighting and floodlighting. The range is 70, 150 and 250W. The outer tubular bulb is made of quartz and so external UV protection is essential. These lamps are warm to neutral colour appearance with three colour temperatures 3000K, 3500K and 4300K, and give good colour rendering (Ra75). Special instant hot re-strike control gear with a very high starting pulse (20kV or more) is available but it is important to check the luminaire is suitable for such high voltages.

Figure 9.13. European metal halide lamps.p>

Sportlight.
The Sportlight range has CSI sealed beam, double ended and single ended lamps rated at 750 Watts and over, designed for exterior floodlighting including TV outdoor broadcasting. They are also used for major sports arenas. All types use control gear specific to the style, supply voltage and wattage. CSI lamps are rated at 1000W and double ended lamps range from 750W to 2000W. Special versions of Sportlight lamps are available for hot re-strike. All style descriptions are prefixed with SPL with the exception of the PAR 64 lamp, prefixed CSI.

Blended Light
Blended light lamps do not require ballasts. They can convert 240V incandescent lamp sockets to mercury by simple lamp replacement. The longer life of the mercury lamp saves replacement labour costs and is an excellent replacement for hard-to-get-at incandescent lamps. The range is from 160W to 500W and all bulbs have the standard Kolorlux phosphor coating. The lamps contain a tungsten filament which acts as the ballast for the mercury arc tube.

Low Pressure Sodium Lamps SOX
All the light produced from sodium lamps comes from vaporised Sodium contained in an arc tube. If the sodium pressure in the arc tube is very low then all the radiation from the discharge appears as yellow light. As the human eye has its maximum sensitivity in this region, yellow lamps can be very efficient. To obtain the low pressure a large arc tube is required which is similar to a compact fluorescent tube but made of a special ply glass with a sodium resistant internal skin. The U shaped arc tube is contained in a glass outer vacuum jacket, with a clear coating which reflects internal infra red energy, to maintain the correct operating temperature. Low pressure sodium lamps are called SOX and the wattages range from 18W to 180W.

The larger versions achieve an efficacy of almost 200 lumens per watt and are the most efficient light source available. However, the yellow colour makes it unsuitable for general interior lighting and their main use is for lighting trunk roads, tunnels, underpasses and for security lighting. SOX lamps require their own control gear with a ballast and ignitor or special ballast only. Because of the quantity of sodium contained in these lamps transportation and disposal must be in an approved manner. Also SOX lamps cannot be used in or above hazardous zones in case fire results from an accidental lamp breakage. Although the lamps have only specific applications the volume of sales is a significant part of the discharge lamp market.

 
Lighting Colour Colour is an important aspect in quality lighting. For example:
  • Products must appear the same in the shop as when the customers use them at home.
  • Colour can be used to create the appropriate mood in restaurants and work places.
  • Colour consistency is necessary for quality control in printing, dyeing, painting, etc.

ThThe primary colours are red, green and blue. Blending these three colours can produce any colour. The colour output of lamps is shown by a Spectral Energy Distribution Curve (SEDC) which shows how much of each colour is emitted. Each colour is defined by its wavelength (measured in nanometres).

Figure 10.1. Colours and wavelength in nanometres.p>

White light is an approximately equal mixture of all the colours in the spectrum, such as natural daylight. The colour mixture of daylight is revealed when we see a rainbow. White light can also be made from the three primary colours, or even two complementary (opposite) colours.

The human eye cannot detect the colour constituents, only the total appearance. It is therefore possible to see two "white" lights that look the same although they are made up from different colour constituents.

The human eye is most sensitive to the yellow-green part of the spectrum so visually efficient light sources tend to concentrate their output in this waveband.

The eye is least sensitive to red and violet, but these colours are needed to provide good colour rendering.

&n 

Figure 10.2. Spectral sensitivity of the eye.p>

The colour sensitivity of the eye changes at very low lighting levels, however for normal artificial lighting photopic vision applies.

The brain can modify the image received by the eye and this is called colour consistency. When the colour of light changes the image seen by the eye changes. However for familiar objects the brain knows they have not actually changed colour and thus adjusts the visual signal.

This effect minimises the changes in daylight and the local effects of reflected light. If you stand in a green field your face will be greener but this will not be noticed unless your photograph is taken. The camera and film records the actual situation and this will be apparent when looking at the photograph.

Colour Rendering
The eye and mind like to see colours appear natural and normal and that requires a light source with good colour rendering.

Such a lamp requires the presence of all colours in a continuous spectrum. See Figure 10.3 (page 6).

The spectral distribution curves give an indication of how a light source will make objects appear. In general:

  • Incandescent and tungsten halogen lamps produce continuous spectra.
  • Fluorescent lamps produce low level continuous spectra but are dominated by one or more peaks.
  • HID lamps produce light in discrete bands or lines.

Lamps with continuous spectra generally produce less distortion of viewed colours and create better colour rendering.

Lamps with selective spectra generally intensify certain colours and reduce others so produce a distorted colour image, which is poor colour rendering.

The two lamps shown in Figure 10.4 (page 6) are made up of different colour constituents but their "white" colour appearance would be very similar.

Specifying Lamp Colour
Two measures are needed to describe lamp colour completely:
Chromaticity (colour appearance) and colour rendering.

There are two ways used to describe chromaticity:

  1. CIE chromaticity co-ordinates. See Figure 10.5 (page 6).
  2. Correlated colour temperature or Kelvin scale. This only applies to incandescent lamps or lamps whose colour coordinates fall on or very near the "black body" locus. This line is indicated on
Figure 10.5 (page 6), and shows how a theoretical black body emits light when heated and how the colour changes as the temperature increases. Kelvin is the temperature scale used.

Colour rendering is more difficult to define but in common use is the Colour Rendering Index (CRI) or Ra. This indicates the amount of colour distortion of a number of specified colour samples (see Figure 10.6 page 6) compared with a standard such as an incandescent lamp. The scale is 0-100 where the higher the value the better the colour rendering.

Note that chromaticity and colour rendering are independent of each other and therefore both performance characteristics need to be considered separately.

However these numerical systems have limitations and visual assessment of the light source illuminating the object is the best form of colour judgement.

Chromaticity refers to the visual "warmth" or "coolness" of colour. CIE chromaticity diagram is a chart with x, y axes to locate every colour.

A mixture of all colours appears white in the centre of the diagram that is roughly triangular in shape with the primary colours red, green and blue forming the corners.

The diagram can be used to compare different colours and will indicate the relative appearance by their positions.

Chromaticity - Kelvin Scale
Temperature chromaticity defines incandescent light source colour in Kelvins (K). As objects get hotter and start to give off light (become incandescent), the colour of the emitted light goes from deep red, red, to yellow, to white, to blue-white and this can be measured on Kelvin temperature scale as chromaticity (see heavy line on Figure 10.5, page 6).

Non incandescent light sources (all discharge lamps including fluorescent) are given Correlated Colour Temperature (CCT) values - as if they emitted light at a Kelvin temperature of their rating, but this is only an approximation and of limited value when comparing the colour appearance of light sources.

Colour Rendering Index (CRI) is an indication of how well a light source renders the colour of objects in a natural or familiar way. The system uses a pallet of pastel colours to visually compare colour shift to an "ideal" light source with the same Colour Temperature. An "ideal" light source has CRI of 100.

High CRI numbers indicate light sources which will make people and objects look natural and normal. But CRI alone does not indicate whether a lamp is suitable for a given task. For example both incandescent lamps ands natural daylight have CRI of 99+, but incandescent is weak in blue. Daylight may be too cold for an intimate restaurant setting as at low lighting levels acceptable "white" light becomes warmer in appearance i.e. a higher red content.

CRI comparison is valid only when comparing sources with the same chromaticity - light sources with different chromaticities may have similar CRI rating but will render colours differently. CRI is not a perfect measure of colour, but is the only internationally recognised indicator of colour rendering ability.

Fluorescent Lamp Colours
The light from fluorescent lamps depends upon the phosphor:

  • Standard Colours (White, Warm White, etc.) provide only moderate colour rendering.
  • Tri-phosphor and Multi-phosphor (Polylux XL) give good to excellent colour rendering.

Special colour lamps are available for aquaria, plant enhancement, etc.

Colour Selection Rules of Thumb
For low lighting levels use warm sources (Polylux XL 827 or 830). For higher lighting levels use cooler colours (Polylux XL 835 or 840).

For general commercial applications Polylux XL should be recommended in place of standard colours because of the combined advantages of longer life, better colour rendering and lamp efficacy.

Colour Rendering Rules of Thumb
For good colour and the best efficacy, Polylux XL should be the first choice. For very good colour use Polylux Deluxe lamps.

For applications where extremely good colour rendering is the overriding factor, such as matching of photographic prints, fabrics and other dyed goods, only fluorescent lamps Northlight (colour 55) and Artificial Daylight (AD) can be used. These lamps have poor light output and have to be changed frequently as light output and light quality reduces rapidly. Only Artificial Daylight meets all the requirements of BS950 (Colour Matching).

Colour Application Notes
Choose paint, furniture and fabrics under the light source to be used in the space.
High intensity discharge lamps can be matched to some fluorescent lamp colours.

  • Multi-Vapor and Kolorarc - Polylux XL 840 and Cool White.
  • Halarc - Polylux 835.
  • Arcstream - Polylux XL 830 and 840.

For landscape lighting and foliage, green copper roofs or statues use mercury vapour lamps that will accentuate the blue and green colours.

For high ceiling stores, sports arenas and industrial areas use Multi-Vapor, Kolorarc or Sportlight lamps.

For general floodlighting, security lighting and car parks where colour is not critical use Lucalox as such lighting operates for long periods and efficacy is important to keep down running costs.

 
N.N.B. The printed colours reproduced here are approximations for use with the module content only p>

 

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