Students: Please check the lightolier.com site for refresher information on Light Sources (lamps) such as incandescent, halogen, fluorescent, compact fluorescent, and HID and ballast information. Lessons 3, 4, 5, 6, and 10 need to be reviewed. Most of the information has been discussed in class. However, take the quiz provided at the end of each lesson to reinforce your learning and also help you with exam 2.
HIGH INTENSITY
DISCHARGE LAMPS:
High Intensity Discharge (HID) Lamps
- consist of Mercury, Metal Halide, and High Pressure Sodium….
- consist of an inner arc tube that contains gas vapors and electrodes,
and
- an outer jacket or bulb made of heat resistant glass.
- The outer bulb protects the arc tube, absorbs ultraviolet radiation
from the arc and maintains a nearly constant temperature
inside the lamp for proper operation.
- The outer bulb may be clear or phosphor coated.
- Light is produced when a high intensity electric discharge takes place
in the gas vapor (fluorescent lamps use a low intensity
arc).
- All HID lamps require some sort of ballasting.
TYPES OF HID LAMPS
MERCURY
- These lamps produce a blue-green light.
- When phosphor coating is used on the interior of the outer glass jacket,
mercury lamps improve in both color quality and
efficacy.
- Some mercury lamps have a ballast built into their base, thus eliminating
the need for auxiliary equipment. However, these self-ballasted
lamps have shorter lamp life and lower efficacies than
standard mercury lamps.
METAL HALIDE
These lamps use various metallic salts, as well as mercury in the arc,
- producing more light per watt and better color than Mercury.
- Since the source of light, the arc, is relatively small, metal halide
allows for good optical control.
- There is usually some color variation from lamp to lamp both initially
and over time;
- however, with new arc tube designs, the use of phosphors, or other metallic
salts, improvements can be achieved in both color and lamp efficacy.
- Metal halide lamps usually have shorter life ratings relative
to mercury and high-pressure sodium lamps.
HIGH PRESSURE SODIUM (HPS)
- Of all lamps in the HID family of light sources, HPS lamps are
the most efficacious.
- Additionally, they have a thin, ceramic arc tube which, because of its
size, allows for very good optical control.
- Sodium is the major chemical component and the reason why the lamp produces
a yellowish color of light.
- There are three types of HPS light sources; standard, deluxe, and white
high-pressure sodium.
- The deluxe HPS and white HPS lamps have better CRIs but lower LPWs relative
to the standard lamp.
BALLAST'S AND STARTERS
- All HID lamps require ballasts to deliver the proper voltage and regulate
the current flow within the arc tube.
- Some Metal Halide lamps employ a starting electrode within the lamp
to initiate the arc.
IGNITION & WARM-UP
- It is not possible to instantly ignite a cold HID lamp to full brilliance.
- All HID lamps employ a mixture of gases and metals in the arc tube.
As power is applied, temperatures and pressure build
gradually, causing vapors of the metals to enter into
the arc and release light energy.
- Igniting the arc sometimes takes a few seconds and the duration of the
warm-up period varies depending on lamp type, ranging
from 2 to 10 minutes (During this period, the lamp will
exhibit different colors as the various metals vaporize).
BALLAST
-
All
gas discharge lamps, including fluorescent lamps, require a ballast to
operate.
- The ballast provides a high initial voltage to initiate the discharge,
then rapidly limits the lamp current to safely sustain
the discharge.
- Ballasts are designed to optimally
operate specific lamp types;
- however, some ballasts will adequately operate more than one type of
lamp. In these cases, optimum lamp performance is generally
not achieved under all conditions.
- Less than optimum conditions may affect the lamp's starting characteristics,
light output, and operating life.
BALLAST FACTOR
The ballast factor is a measure of the actual lumen output for a specific
lamp on a commercial ballast relative to the rated lumen output for that
same lamp measured on a reference ballast under ANSI test conditions (open
air at 25C [77F]). You will find this information in all ballast manufacturers'
literature.
LAMP-BALLAST SYSTEM EFFICACY
The efficiency of a fluorescent system depends on the lamp-ballast combination.
Similarly, lamp efficacy is affected by ballast technology; the same lamp
will perform differently when operated by a magnetic ballast than it will
when operated by an electronic ballast.
FLUORESCENT BALLAST
CIRCUIT TYPE AND OPERATING MODE:
- Fluorescent ballasts are manufactured for three primary types of fluorescent
lamps: preheat, rapid start, and instant start.
ELECTRONIC BALLASTS
(SOLID STATE)
- Electronic high-frequency ballasts increase system efficacy, which leads
to increased energy efficiency while lowering operating costs.
- Electronic ballasts take incoming 60 Hz power and convert it to high-frequency
(20 to 40 kHz).
- Electronic ballasts are more efficient than magnetic ballasts in the
operation of fluorescent lamps.
- Operating at higher frequencies electronic ballasts reduce end losses
resulting in an overall system efficacy increase of
15% to 20%.
- Dimming capabilities
MAGNETIC BALLASTS
(ELECTROMECHANICAL)
- Manetic ballasts operate at 60 Hz power
- Noisy and less efficient
- No dimming capabilities
ADJUSTABLE OUTPUT/ELECTRONIC
DIMMING BALLASTS
Electronic dimming ballasts permit the light output of a lamp to
be continuously controlled over a range of approximately 10% to 100% of
full light output. A low voltage signal (usually between 0 and
10 volts) to the ballast output circuit modifies the current to the lamp.
Electronic dimming ballasts are equipped with feedback circuits that maintain
electrode voltage when the lamp current is reduced. This allows
the lamp to be dimmed over a wide range without reducing lamp life.
AUDIBLE NOISE
- One characteristic of magnetic ballasts operating at 60 Hz is
the generation of audible noise. This is due to the vibration
of the steel laminations.
- The best ballasts use high-quality materials and workmanship
to reduce noise.
- Noise is rated A, B, C, or D in decreasing order of preference.
- “A” sound rated ballast is the least noisy. “D” rated ballasts are the
noisiest.
- All electronic ballasts have an “A” rating.
HID BALLASTS
- HID lamps require ballasts to regulate current and deliver the proper
voltage to the arc. .
- Ballasts for HID lamps may be incorporated into the body of a luminaire
as a core and coil or encased in their own metal compartment.
This becomes useful where separation of the ballast from the housing is
desirable.
- A few electronic ballasts are now available for HID lamps (Their primary
benefit is a more precise management of the lamp's arc tube wattage
over life; thus resulting in more consistent color and longer lamp life)