J10 HID Lamps and Ballasts

11 HID LAMPS & LPS LAMPS

This Guide will concentrate on two types of High Pressure Discharge (HID) lamps and ballasts = Metal Halide (MH), High-Pressure Sodium (HPS) – and low-pressure discharge Low Pressure Sodium (LPS) lams and ballasts. For the sake of simplicity, all three technologies will be referred to as HID Lamps and Ballasts. Another type of HID lamp, the Mercury-Vapor (MV) lamp will only be covered in a cursory manner. MV lamps are becoming obsolete as the other three HID lamps offer increased efficacy, color rendering and lumen maintenance at a lower cost.

All HID lamps operate on the same principle. Simply out, when the lamp is turned on, a voltage is applied to initiate an arc at an electrode, which discharges and vaporizes mercury and other metal halides. The energized metal atoms emit light and as they cool convect back into the electric arc to continue the process. All HID lamps, require a ballast to produce the arc.

a. Mercury Vapour (MV) Lamps
Use of MV Lamps should be discouraged. They are no more efficient than fluorescent applications in indoor applications, in outdoor applications they should be replaced with one of the other gas discharge lamps.

Applications

  • MV lamps increased in use during the 1940s in industrial and commercial applications due to their longer life and efficacy when compared to standard incandescent lamps. MV lamps are no longer specified for new construction or retrofit due to poor efficacy compared to other HID and fluorescent lamps.
  • • It is economical to replace MV lamps with metal halide or high pressure sodium (HPS) lamps, which have much better luminous efficacy. These direct replacement lamps may improve the efficacy by 70%+.
  • • The disposal of mercury vapour lamps will require special disposal methods because of the mercury inside the lamp.
  • • Local

disposal authorities should be contacted for approved disposal methods.

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b. Metal Halide Lamps

Construction
• The metal halide (MH) lamps are generally similar in construction to the MV lamps.
• They operate on the same principle as all HID lamps.
• The main difference is that the arc tube contains metallic salts (scandium and sodium) in addition to the mercury vapour and argon gas.
• Like all HID sources, MH lamps consist of an arc tube enclosed in an outer bulb.

Typical Construction and Circuit of a MH Lamp

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Note: Pulse Start lamp uses higher open circuit voltage for starting.

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BT :Bulged-tubular
T :Tubular
Numbers indicate maximum diameter in eighths of an inch.

Characteristics

Colour • MH lamps are available in both clear and phosphor-coated versions.
• Clear lamps produce a slightly bluish-white colour and have a CRI far superior to MV lamps.
• Phosphor-coated lamps produce a warmer-looking white light and an improved CRI.
• MH lamps exhibit some colour variation from lamp to lamp and normally change colour throughout their life
Colour rendering index • CRI - 65-70
Colour temperature
Luminous efficacy • The MH lamp is the most efficient source of “white” light available.
• Efficacies range from 50 to 110 lumens per watt.
• MH lamps are more efficient than MV and fluorescent lamps, but less efficient than HPS and low pressure sodium (LPS) lamps.
Lamp life (hours) Rated Average Life
• 6,000 hours (70 W) to 20,000 (400 W).
Lamp watts Available Wattage
• Sizes range from 40 to 1,500 watts.
Lamp lumen
Warm-up time • Warm-up time is about 4 minutes.
Restrike time • Restrike time is about 10-12 minutes standard - 4-7 min. for pulse start.
Lamp cost
Main applications
• Similar to MV lamps.
• MH lamps are effective replacements for MV lamps.
• Large wattages are used for floodlighting, streetlighting, large industrial areas and sports arenas.
• Smaller wattages are used in merchandising areas, assembly spaces, schools and public buildings.
• Clear lamps are used for colour TV broadcasting, colour photography, industrial/commercial lighting.
• Phosphor-coated lamps are used for industrial/commercial indoor lighting, area lighting.
Brands
Major manufacturers carry a variety of metal halide lamps.
Operation • Fixtures with MH lamps should be fully enclosed.
• MH and MV lamps operate under high pressure and very high temperatures and there is a possibility that the arc tube may rupture. When this happens, the outer bulb surrounding the arc tube may break, and particles of extremely hot quartz (from the arc tube) and glass fragments (from the outer bulb) create a risk of personal injury or fire.
• Manufacturer’s instructions must be followed when installing and operating MH lamps.

• MH lamplife and output is dependent on the installation position specidied in the manufacturer’s specifications. Manufacturer’s recommendations must be followed in order to minimize lamp failure.
• Horizontal-burning lamps have the arc tube bowed upward, to follow the natural curve of the arc stream in the horizontal burning position.

Direct Replacement of MV Lamps – MH Lamps
• Some MH lamps are designed as direct replacements for MV lamps and use the existing MV lamp fixtures and ballasts.
• In comparison with the MV lamps, the efficacy may be improved by 70%+, but the rated average life is generally shorter.

Replacement of Incandescent PAR Lamps - Ceramic MH Lamps

• In order to counter the poor colour consistency of metal halide lamps over life, lamp manufacturers have combined the ceramic arc tube from HPS lamps with the gas mix and metals used in Metal Halide lamps to produce Ceramic Metal Halide (CMH) lamps.
• These lamps offer significant advantages over typical Metal Halide lamps and are available in PAR packages to fit smaller recessed and track-mounted luminaires. • These sources and luminaires offer significant savings compared to incandescent lamps typically used in retail (stores) and display lighting.

Comparison

Lamp Wattage Rated Lamp Life (hrs) MBCP? Initial
Lumens Colour
120 W Halogen PAR 38 Flood:
25°, 3,000 7,700 1,800 95 CRI
39 W CMH PAR 30 Flood
(55W with electronic ballast):
30° , 9,000 , 7,400 , 2,300 85 CRI

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c. High Pressure Sodium Lamps

Construction
• High pressure sodium (HPS) lamps are HID lamps that ionize sodium vapour.
• Like all HID sources, HPS lamps consist of an arc tube enclosed in an outer bulb.
• The arc tube contains xenon (starting gas), sodium and mercury.
• The mercury is in the form of an amalgam with the sodium.
• HPS lamps do not have starting electrodes because of the arc tube’s small diameter.
• The arc tube is made of a ceramic that can withstand high temperatures (1,300°C) and resist the corrosive effects of hot sodium.

Typical Construction and Circuit of an HPS Lamp
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Shapes

Shape Codes
B : Bullet
BT : Bulged-tubular
E : Elliptical
PAR : Parabolic aluminized reflector
T : Tubular
Numbers indicate approximate maximum diameter, in eighths of an inch.

Colour • The light colour of HPS lamps is usually described as golden-white.
• HPS lamps are available in either clear or diff use-coated versions.
• Improved colour lamps operating under increased pressure have better colour rendering properties at the expense of lamp life and luminous efficiency.
Colour rendering index
Colour temperature
Luminous efficacy • HPS lamps are the most efficient source of golden-white light.
• HPS lamps are more efficient than MH lamps, but less efficient than Low Pressure Sodium (LPS) lamps.
• Efficacies range approximately from 50 to 140 lumens per watt.
• Efficacy increases with lamp size.
Lamp life (hours) • 24,000 hours for most HPS lamps.
Lamp watts • HPS lamp sizes range from 35 to 1,000 watts.
Lamp lumen
Warm-up time • Warm-up time is three to four minutes.
Restrike time • Restrike time is about one minute—shortest restrike time of all HID sources.
Lamp cost
Main applications
• All applications where colour is less important.
• Clear lamps are used in roadway lighting, floodlighting,
industrial lighting, area lighting, airport lighting.
• Coated lamps are used in area and floodlighting, security lighting, industrial and commercial indoor lighting and parking lots.
Operation • The ballast provides a high-voltage pulse (2,500 V) for one microsecond for lamp start.
• This high-voltage spike establishes the xenon arc between the main electrodes.
• Mercury and sodium then vaporize rapidly and maintain the arc.

Direct Replacement of MV Lamps
• Some HPS lamps are designed as direct replacements for MV lamps and use the existing MV lamp fixtures
and ballasts.
• In comparison with the MV lamps, the efficacy may be improved by 70%+, but the rated average life is
generally shorter.
• Often used in energy conservation retrofits.
• For lamp information, refer to the table below:

d. Low Pressure Sodium Lamps
Construction
• Low pressure sodium (LPS or SOX) lamps are HID lamps, operated at low pressure, in which the arc is carried by ionized sodium vapour.
• LPS lamps are more closely related to fluorescent than HID lamps, since they have a low-pressure, low-intensity discharge source and a linear lamp shape.
• An LPS lamp consists of a U-shaped arc tube enclosed in a clear tubular outer bulb.
• An indium oxide coating on the inside of the outer bulb reflects most of the infrared radiation back to the arc tube.
• The arc tube is enclosed in a vacuum to minimize heat loss.
• The lamp is designed to fully utilize its generated heat.
• The arc tube can maintain an operating temperature of about 2,600°C, resulting in an extremely high luminous efficacy.

Typical Construction

Colour • The light of an LPS lamp has a yellow colour (monochromatic).
• The colour rendition is very low—it turns every colour to either yellow or muddy brown.

Colour rendering index • The CRI value does not apply to this lamp.
Colour temperature
Luminous efficacy • The LPS lamp has the highest efficacy of all light sources.
• Lamp efficacies range from 100 to more than 180 lumens per watt.
• Efficacy increases with lamp size.
• The LPS lamp has the highest efficacy because it emits monochromatic yellow light close to the peak of the eye sensitivity curve.
Lamp life (hours) • SOX 18 - 14,000 hours
• Others - 18,000 hours
Lamp watts LPS lamp sizes range from 18 to 180 watts.

Lamp lumen
Warm-up time • about nine minutes.

Restrike time • less than one minute.
Lamp cost
Main applications
• All applications where colour rendering is not important
• Roadway lighting
• Security lighting
• Area floodlighting
• Warehouses
Operation • At start-up, the current is carried by the starting gas (neon
and argon) producing a red glow.
• As the lamp warms up, sodium is vaporized and the
discharge begins to exhibit the characteristic yellow colour of an LPS lamp.

10 HID LAMP BALLASTS

a. Ballasts General
Like fluorescent lamps, HID lamps are electric discharge lamps. A ballast is required to provide proper starting and operating voltage and current in order to initiate and sustain the arc.
b. Probe Start Ballasts
The standard core and coil HID ballast or probe start ballast consists of a series of electrical coils on a core of steel laminations. The coils are impregnated with a varnish to provide electrical insulation, reduce noise and dissipate heat. Some ballasts for interior use are housed in metal cans and potted with insulating materials.
c. Pulse Start Ballasts
• Pulse start HID Ballasts incorporate a different starting technique which reduces ballast losses and increases lamp performance.
• Pulse start retrofits can be a good measure for existing metal halide installations in schools, industrial and commercial projects.
• A 320 W metal halide pulse start system can replace a 400 W system.
• The pulse start lamp gives less lamp lumen depreciation, better colour consistency over lamp life, and faster hot restrike.
d. Electronic HID Ballasts
Designed primarily for the low wattage Ceramic Metal Halide lamps, the electronic HID ballasts are gradually expanding to higher lamp wattages.
Advantages
• Significantly smaller size and lower weight than core and coil systems.
• More efficient, up to 20% savings over conventional ballasts.
• Square wave output increases lamp life.
• Automatic end-of-life detection; shuts lamp down instead of trying to restart.

J10. HID LAMP BALLASTS
a. Ballasts General
Like fluorescent lamps, HID lamps are electric discharge lamps. A ballast is required to provide proper starting and operating voltage and current in order to initiate and sustain the arc.

b. Probe Start Ballasts
The standard core and coil HID ballast or probe start ballast consists of a series of electrical coils on a core of steel laminations. The coils are impregnated with a varnish to provide electrical insulation, reduce noise and dissipate heat. Some ballasts for interior use are housed in metal cans and potted with insulating materials.

c. Pulse Start Ballasts
o Pulse start HID Ballasts incorporate a different starting technique which reduces ballast losses and increases lamp performance.
o Pulse start retrofits can be a good measure for existing metal halide installations in schools, industrial and commercial projects.
o A 320 W metal halide pulse start system can replace a 400 W system.
o The pulse start lamp gives less lamp lumen depreciation, better colour consistency over lamp life, and faster hot restrike.
d. Electronic HID Ballasts
Designed primarily for the low wattage Ceramic Metal Halide lamps, the electronic HID ballasts are gradually expanding to higher lamp wattages.

Advantages
o Significantly smaller size and lower weight than core and coil systems.
o More efficient, up to 20% savings over conventional ballasts.
o Square wave output increases lamp life.
o Automatic end-of-life detection; shuts lamp down instead of trying to restart.