Different Type of Lamps for Luminous
March 20, 2011 5 Comments
- Artificial luminous radiation can be produced from electrical energy according to two principles:
- Incandescence: It is the production of light via temperature elevation. The most common example is a filament heated to white state by the circulation of an electrical current. The energy supplied is transformed into heat by the Joule effect and into luminous flux.
- Luminescence: It is the phenomenon of emission by a material of visible or almost visible luminous radiation. A gas (or vapours) subjected to an electrical discharge emits luminous radiation (Electroluminescence of gases). Since this gas does not conduct at normal temperature and pressure, the discharge is produced by generating charged particles which permit ionization of the gas.
- The nature, pressure and temperature of the gas determine the light spectrum. Photoluminescence is the luminescence of a material exposed to visible or almost visible radiation (ultraviolet, infrared).When the substance absorbs ultraviolet radiation and emits visible radiation which stops a short time after energization, this is fluorescence.
- Incandescent lamps are historically the oldest and the most often found in common use. They are based on the principle of a filament rendered incandescent in a vacuum or neutral atmosphere which prevents combustion.
A distinction is made between:
- Standard Incandescent bulbs
- These contain a tungsten filament and are filled with an inert gas (nitrogen and argon or krypton).
- Halogen Incandescent bulbs
- These also contain a tungsten filament, but are filled with a halogen compound and an inert gas (krypton or xenon). This halogen compound is responsible for the phenomenon of filament regeneration, which increases the service life of the lamps and avoids them blackening. It also enables a higher filament temperature and therefore greater luminosity in smaller-size bulbs.
The main disadvantage of incandescent lamps is their significant heat dissipation, resulting in poor luminous efficiency.
- This family covers fluorescent tubes and compact fluorescent lamps. Their technology is usually known as “low-pressure mercury”.
- In fluorescent tubes, an electrical discharge causes electrons to collide with ions of mercury vapor, resulting in ultraviolet radiation due to energization of the mercury atoms.
- The fluorescent material, which covers the inside of the tubes, then transforms this radiation into visible light.
Fluorescent tubes dissipate less heat and have a longer service life than incandescent lamps, but they do need an ignition device called a “starter” and a device to limit the current in the arc after ignition. This device called “ballast” is usually a choke placed in series with the arc.
- Compact fluorescent lamps are based on the same principle as a fluorescent tube. The starter and ballast functions are provided by an electronic circuit (integrated in the lamp) which enables the use of smaller tubes folded back on themselves.
- Fluorescent tube
- HP mercury vapour
- High-pressure sodium
- Low-pressure sodium
- Metal halide
Applications of Bulbs:
|Standard Incandescent bulbs||– Domestic use
– Localized decorative lighting
|– Direct connection without intermediate switchgear
– Reasonable purchase price
– Compact size
– Instantaneous lighting
– Good color rendering
|– Low luminous efficiency and high electricity consumption
– Significant heat dissipation
– Short service life
|Halogen Incandescent bulbs||– Spot lighting
– Intense lighting
|– Direct connection
– Instantaneous efficiency
– Excellent color rendering
|-Average luminous efficiency|
|Fluorescent tube||– Shops, offices, workshops
|– High luminous efficiency
– Average color rendering
|– Low light intensity of single unit
– Sensitive to extreme temperatures
|HP mercury vapor||– Workshops, halls, hangars- Factory floors||– Good luminous efficiency
– Acceptable color rendering
– Compact size
– Long service life
|– Lighting and relighting time
of a few minutes
– Large halls
|– Very good luminous efficiency||– Lighting and relighting time
of a few minutes
|Low-pressure sodium||– Outdoors
– Emergency lighting
|– Good visibility in foggy weather
– Economical to use
|– Long lighting time (5 min.)
– Mediocre color rendering
|Metal halide||– Large areas
– Halls with high ceilings
|– Good luminous efficiency
– Good color rendering
– Long service life
|– Lighting and relighting time
of a few minutes
|LED||– Signaling (3-color traffic lights, “exit” signs and emergency lighting)||– Insensitive to the number of switching
– Low energy consumption
– Low temperature
|– Limited number of colors
– Low brightness of single
Type of HID (High Intensity Discharge) Lamp:
- The term High Intensity Discharge or HID describes lighting systems that produce light through an electrical discharge which typically occurs inside a pressurized arc tube between two electrodes. In general, these systems feature long life, high light output for the size of the lamp and increased efficiency compared to fluorescent and incandescent technologies. HID lamps are named by the type of gas and metal contained within the arc tube. There are five different families of HID: Mercury Vapor, High Pressure Sodium, Quartz Metal Halide, Pulse Start Quartz Metal Halide, and Ceramic Metal Halide.
- HID lamps require a ballast to operate. Typically, the HID ballast (sometimes with the addition of a capacitor and igniters) serves to start and operate the lamp in a controlled manner.
- HID lamps take several minutes to warm-up. Full light output is reached after the arc tube temperature rises and the metal vapours reach final operating pressure. A power interruption or voltage drop will cause the lamp to extinguish. Before the lamp will re-light, it must cool to the point where the lamp’s arc will re strike.
- There are four basic types of lamps considered as HID light sources:
- Mercury vapour,
- Low pressure sodium,
- High pressure sodium and
- Metal halide.
- All are arc discharge lamps. Light is produced by an arc discharge between two electrodes at opposite ends of the arc tube within the lamp.
- Each HID lamp type has its own characteristics that must be individually considered for any lighting application.
(1) High Pressure Sodium
- Efficacy: 80 to 140 lumens per watt.
- Life: A long lamp life of 20,000 to 24,000 hours, and the best lumen maintenance of all HID sources.
- Wattages: 35W to 1000W and the warm-up time is from 2 to 4 minutes.
- Re-strike time: Approximately 1 minute.
- Applications: Roadway lighting
- High pressure sodium and metal halide lamps comprise the majority of HID lighting applications.
- The biggest drawback of high pressure sodium is the yellowish colour light output, but it is acceptable for use in many industrial and outdoor applications (e.g. Roadway lighting).
(2) Low Pressure Sodium
- Low pressure sodium (LPS) lamps are grouped with HID lamps, but in fact do not have a compact, high intensity arc. They are more like a fluorescent lamp with a long stretched-out arc.
- Colour: LPS lamps have no colour rendering index as the colour output is monochromatic yellow.
- Efficacy: 100 to 185 lumens per watt
- Wattages: 18W to 180W
- Life: Average 14,000 to 18,000 hour lifetimes.
- Re-strike time: shortest re-strike time among HID sources only 3 to 12 seconds.
- Applications: LPS has few viable applications beyond street, parking lot and tunnel lighting.
- They have excellent lumen maintenance but the longest warm up times, from 7 to 15 minutes.
(3) Metal Halide
- Efficiency: Efficacy of 60 to 110 lumens per watt
- Warm-up Time: 2 to 5 minutes.
- Re-strike time: 10 to 20 Minutes.
- Wattages: 20W to 1000W
- Life: 6,000 to 20,000 hours.
- Applications: This technology is ideal for Lamp applications requiring truer colour as in fruit, vegetable, Clothing and other accent lighting in retail displays.
- Wattages from 1500W to 2000W are specialty lamps used for sports lighting, and have lamp life ratings of only 3000 to 5000 hours.
- Advantages: The advantage of metal halide lighting is its bright crisp, white light output suitable for commercial, retail, and industrial installations where light quality is important. However, lumen maintenance over the life of the lamps is less than optimal relative to other HID sources.
- The arc tube material for metal halide lamps was quartz until 1995 when ceramic arc tube technology was developed.
- Ceramic arc tubes are now predominantly used in low wattage (20W to 150W) lamps, though new designs up to 400W have emerged in recent years.
- Ceramic arc tubes provide improved Colon consistency over lamp life.
How Lamp starts:
- In cold state mercury vapor and halides are in non-ionized state. Impedance between two electrodes are very high. To overcome this impedance we need to ionize the mercury vapor. A high amplitude pulse in the order of 3.5 KV or more with sufficient energy that can create an initial arc. Minimum limit for amplitude has been specified in IEC60926/927 specification.
- Ignitor pulses continue to support ionization till current through the lamp becomes 90 percent of the rated value or voltage across the lamp 110 percent of rated value. Declared life of lamp is based on one switching per 24 hours.
- In many parts of Asia frequent power supply interruption is very common. For example in eastern India average 5 to 6 power supply interruption observed per 12 hours burning of the lamp per day. So the lamps are also switched on/off 5 to 6 times during their 12 hours burning (Average) per day.
- This causes repeated dissolution /erosion of thorium coated tungsten electrode. This phenomenon is also observed in indoor sports stadium where lamps are repeatedly switched on/off according to sports fixture. to save energy. So we find there are two parameters, which determine the life of Metal Halide and other HID lamp
- (i) Ageing- No of burning hours.
- (ii) Switching- No of switching on/off cycle.
- Till date, data supplied by lamp manufacturer for successful ignition is
- (a)Minimum amplitude of ignitior pulses
- (b) Pulse duration.
- Maximum energy content of ignitor pulse is unrestricted, it has been also not specified in IEC60926/927 specification. Field report from luminaries manufacturers say
- (a) Lamp failures in 18 meter tower(lighting Mast) are less than 6 meter tower ,where as components such as pulse ignitor (internationally certified) ,ballast and lamps and luminaries are same( control gear for the luminaries are at the bottom of the tower)
- (b) 30 percent of Metal Halide Lamps in street light fails in 6 months or early when pulse ignitors used compare to superimposed ignitor( ignitor which can ignite lamp at short distance).
- Metal Halide lamp with long distance ignitor used inbuilt into the luminaries has more failure than ignitor which can ignite lamp at short distance.
What is Dragon Kink:
- Maximum energy which lamp can be successfully subjected is termed as critical energy (Le) Typically 0.75 mJ (may vary depending on discharge tube parameter).
- High amplitude high energy ignition pulses greater than critical energy(Le) causes dissolution / erosion of electrode of Metal Halide(M.H) and Sodium vapor (SON) lamp, this results in increase in minimum ignition energy required to ignite a Metal Halide(M.H) /Sodium vapor (SON) lamp with increase in number of switching ON/OFF operation .
- Higher the energy content of high amplitude pulses of ignitor, rapid is the increase in minimum ignition energy at which HID lamp ignites for subsequent switching on.
- This phenomena of increase in minimum ignition energy required to start Metal Halide(M.H) and Sodium vapor (SON) lamp with increase in no of switching on/off due to impact of high energy pulses of Ignitor is named as “Dragon Kink” effect. This phenomena is more prominent in Metal Halide lamp.
- This phenomenon of increase of ignition energy with no of switching on/off determines switching life of the lamp. However this increase of ignition energy which can start a lamp with increase in no of switching on/off cycles could be almost arrested if lamps are ignited with ignitor pulses reaching lamp has energy content less than critical energy(Le).
- In the summary we can say that we need to develop an ignitor system that takes care of ‘Dragon Kink’effect
- (I) Energy content of igniter pulses across the lamp are adequate for stating but below critical limit (Le) as need to be declared by lamp manufacturer/IEC specification for ensuring availability of total useful life by preventing early switching life failure.
- (II) Useful minimum and maximum distance marked on the ignitor to take into account of Dragon Kink effect so that full switching life of Metal Halide Lamp/other HID lamp is available
GENERAL BALLAST DESCRIPTION:
- HID lamps provide light from an electric discharge or arc and have a negative resistance characteristic that would cause them to draw excessive current leading to instant lamp destruction if operated directly from line voltage.
- The ballast is a power supply for arc discharge lamps. Its purpose in HID lighting is to provide the proper starting voltage to initiate and maintain the lamp arc and to sustain and control lamp current once the arc is established.
- Ballasts and lamps are designed to meet standards for interchange ability between lamps and ballasts of the same type and wattage. A lamp must be operated by the ballast designed for that lamp, as improper matching of lamp and ballast may cause damage to the lamp or ballast or both.
- For many years all HID ballasts were magnetic ballasts operating at the power line frequency of 50 or 60 Hertz to provide proper lamp operation.
- In the past few years electronic ballasts have been developed, primarily for metal halide lamps, using integrated circuits that monitor and control lamp operation. Electronic ballast circuits sense lamp operation characteristics and regulate lamp current to operate the lamp at constant wattage, thus providing a more uniform light output and color rendition throughout lamp life.
- They also sense lamp end of life and other circuit conditions and shut down the ballast when the lamp operating characteristics fail to meet operating specifications
Type of HID (High Intensity Discharge) Ballast:
- HID lamps, like fluorescent lamps require a ballast to provide the proper starting voltage for the lamp and limit the operating current once the lamp is ignited. HID lamps have negative impedance, which means that the lamp draws more current than is required for it to operate. Without ballast, running in this negative impedance condition, the lamp would self-destruct in a very short period of time.
- HID ballasts are classified by the type of circuit they use
- Electromagnetic Ballast (EM):
- Reactor (R).
- High Reactance Autotransformer (HX).
- Constant wattage Autotransformer (CWA)
- Magnetic Regulator.
- Electronic Ballast.
- Further HID ballasts are classified by the type of Power Factor
- High Power Factor (HPF)
- Normal Power Factor (NPF).
(A) Electromagnetic Ballasts (EM)
- Electromagnetic Ballasts use magnetic components to start and regulate the operation of a lamp. Inductors are used as the current limiting component in EM ballasts. Although the inductor is very good at regulating current, it causes a phase shift input of the current waveform creating a non-ideal power factor. Often times a Capacitor is used in Electromagnetic Ballasts to correct
(1) Reactor (R):
- Single coil ballast can be used when the input voltage to a fixture meets the starting and operating voltage requirements of an HID lamp. In this situation, the reactor ballast performs only the current-limiting function since the voltage necessary to initiate the ignitor pulses, and start and sustain the lamp comes directly from the input voltage to the fixture.
- The reactor ballast is electrically in series with the lamp.
- There is no capacitor involved with the operation of the lamp. Because of that, the lamp current crest factor is desirably low, in the 1.4 to 1.5 range.
- Without a capacitor, the reactor ballasts are inherently normal power factor devices (50%). When desired to reduce the ballast input current required during lamp operation, a capacitor may be utilized across the input line to provide high power factor (90%) operation, but the addition of the capacitor will not affect how the ballast operates the lamp.
(2) High Reactance Autotransformer (HX):
- When the input voltage does not meet the starting and operating voltage requirements of the HID lamp, a high reactant auto transformer ballast can be used. In addition to limiting the current to the lamp, an HX ballast transforms the input voltage to the lamp’s required level.
- Two coils, called the primary and secondary, are employed within the ballast. The operating characteristics, such as lamp wattage regulation are similar to the reactor.
- The high reactance auto transformer ballast is also inherently a normal power factor (50%) ballast but can be corrected to a high power factor (90%) with the addition of a capacitor across the primary coil. As with the reactor ballast, the addition of this capacitor does not affect the lamp’s operation.
- Both reactor and high reactance ballasts provide the same degree of lamp wattage regulation. For example, a simple 5% change in line voltage results in a 10-12% change in lamp operating wattage. However, this fair degree of lamp regulation is acceptable for many applications.
- Slightly higher in cost than reactors, but
- less than regulated type ballasts
- Lower ballast losses than regulator types
- Provides good wattage regulation when line voltage is controlled within ± 5%
- Can be used with 120V, 208V, 240V, 277V,and 480V supply.
- High operating current
- Higher starting current
- Poor regulation
(3) Constant Wattage Autotransformer (CWA), “Peak Lead Autotransformer”:
- To correct the higher input current associated with reactor and high reactance ballasts, and to provide a greater level of lamp wattage regulation, the 2-coil CWA ballast was developed.
- It is the most commonly used ballast circuit for medium and high wattage (175W – 2000W) applications and typically represents the best compromise between cost and performance.
- The CWA is a high power factor ballast utilizing a capacitor in series with the lamp rather than across the input. The capacitor works with the core-and-coil to set and regulate the lamp current to the prescribed level.
- The CWA ballast provides greatly improved lamp wattage regulation over reactor and high reactance circuits. A ± 10% line voltage variation will result in a ± 10% change in lamp wattage for metal halide.
- The metal halide and high pressure sodium ballasts also incorporate wave shaping of the open circuit voltage to provide a higher peak voltage than a normal sine wave.
- This peak voltage (along with a high voltage ignition pulse when an ignitor is used) starts the lamp and contributes to the lamp current crest factor (typically 1.60 -1.65).
- With the CWA ballast, input current during lamp starting or open circuit conditions does not exceed the input current when the lamp is normally operating. CWA ballasts are engineered to tolerate 25-30% drops in line voltage before the lamp extinguishes (lamp dropout), thus reducing accidental lamp outages.
(4) Constant Wattage Isolated (CWI):
- The CWI ballast is a two-coil ballast similar to the CWA ballast except that its secondary coil is electrically isolated from the primary coil.
- This isolated design permits the socket screw shell to be grounded for phase-to-phase input voltage applications such as 208, 240 and 480 volt inputs.
- High power factor (over 90%) and low operating current
- Good regulation–permits and responds favorably to line voltage
- Slightly larger in size and weight thanvariations of up to +5% or –10% Reactor Ballast
- Starting current is even lower than operating current
- Costs less than magnetic regulator
- Provides good regulation of lamp wattage, especially in nominal and below normal systems
- Ballast losses are less than for magnetic regulator.
- More expensive than Reactor type ballast
- Available for all standard voltages
(5) Magnetic Regulator
- Magnetically Regulated (Mag Reg) and Regulated Lag (Reg Lag) are another type of EM ballasts. They utilize a magnetic with three separate coils. One coil connects to a capacitor for increased Power Factor and to regulate current into the lamp coil. The lamp coil is isolated from the power supply. This circuit provides very good control over light output. In some ballast designs, large changes in voltage cause very small changes in lamp wattage
- High power factor (over 90%)
- Excellent line voltage regulation, it is responsive to systems that operate
- normally in extremely high or extremely low line voltage situations–in the “near to ± 10%” range
- Low operating current and lower starting current
- Isolated secondary reduces danger of electrical shock
- At nominal voltage, its volts/watts trace is quite like the performance of a Reactor Ballast
- Provides better lamp regulation.
- Most expensive of all types of ballasts
- Heavier and larger than other ballasts
(2) Electronic HID (e HID) Ballasts:
- There are two basic designs for electronic HID ballasts:
- Low frequency square wave (typically used for low-wattage lamps or with ceramic arc tube lamps in the 250W-400W range) and
- High frequency (for medium wattage lamps in the 250W to 400W range).
- Both make use of integrated circuit technology to provide closer regulation and control of lamp operation over a variety of input voltage and lamp aging conditions.
- The integrated circuits in both types of ballasts continuously monitor input line voltage and lamp conditions and regulate lamp power to the rated wattage. If any power line or lamp circuit condition exists that will cause the lamp or ballast to operate beyond their specified limits the ballast shuts down (removes power from the lamp) to prevent improper operation.
- Electronic HID ballasts improve lamp life, lamp lumen maintenance, and system efficiency.
- Integrated circuit control allows most electronic ballasts to operate at multiple input line voltages and, in some cases, operate more than one lamp wattage. The lamps are operated with constant lamp power that provides better light output regulation and more consistent light color over the life of the lamp.
- Some electronic HID ballasts also offer a continuous dimming function that will dim the lamp to 50% (minimum) lamp power using 0-10V (DC) dimming control voltage.
- All functions required to correct power factor, line current harmonics, and to start and control lamp operation are inherent in the ballast.
- The lamp socket must be pulse rated (dependant on lamp type) because there is an ignition pulse supplied to start the lamp.
Component if HID (High Intensity Discharge):
- All HID lamps are negative resistance light sources (this means that once the arc is initiated, the lamp’s resistance continually decreases as current increases; for all practical purposes, the lamp becomes a short circuit). They require a support device (ballast), that limits the lamp and line current when voltage is applied, to prevent the lamp from being destroyed.
- In addition, the ballast provides the lamp with proper voltage to reliably start and operate the lamp throughout its rated service life. If a transformer is integral to the ballast circuit, it modifies the available supply voltage to provide the voltage required for the lamp.
- A distinction must be made between lag circuit and lead circuit ballasts. The lamp current control element of a lag circuit ballast consists of an inductive reactance in series with the lamp. The current control element in lead circuit ballasts consists of both inductive and capacitive reactance in series with the lamp; however, the net reactance of such a circuit is capacitive in mercury and metal halide ballasts, and inductive in high pressure sodium ballasts.
- High pressure sodium (HPS) lamps are greatly different than the mercury or metal halide lamps. Mercury and metal halide lamps maintain a relatively stable voltage drop across the arc tube throughout its life (wattage is also essentially constant) with aging being reflected only in lamp lumen depreciation, decreasing light output.
- The HPS lamp is a dynamic device with performance changing as the lamp ages. The arc tube voltage rises with usage; therefore, the wattage and lumen output change with age.
- All high power factor (HPF) Reactor (R) and High Reactance (HX) ballasts, as well as all Constant Wattage Autotransformer (CWA), Constant Wattage Isolated (CWI) and Regulated Lag ballasts require a capacitor.
- With core and coil and encapsulated core-and-coil units the capacitor is a separate component and must be properly connected electrically.
- The capacitor for outdoor weatherproof, indoor enclosed-can and postline types is already properly connected within the assembly.
- Two types of capacitors are currently in use:
- Dry metalized film and
- Present capacitor technology has allowed all but a few capacitor applications to be dry film. Oil-filled capacitors are used only when dry film technology cannot satisfy capacitor voltage requirements.
Dry Metalized Film Capacitors:
- Available to fill almost all needs for HID ballast applications.
- Advance dry film capacitors typically require only half the space used by oil filled capacitor and do not require additional spacing for safety.
- The compact, light weight, cylindrical non-conductive case and two insulated wires or terminals reduce the required mounting space as compared with oil-filled capacitors.
- The discharge resistors (when required) are installed within the capacitor case. Dry film capacitors are UL Recognized and contain no PCB material.
- The maximum allowed dry film capacitor case temperature is 105°C.
- Contain non-PCB oil and are a UL-Recognized component. Oil-filled capacitors are only supplied with ballasts where the capacitor operating voltage cannot be satisfied by dry film capacitors.
- When required, the capacitor discharge resistor is connected across the capacitor terminals.
- Additional precautions must be taken when an oil filled capacitor is installed.
- Underwriters Laboratories, Inc. (UL) requires clearance of at least 3/8 inch above the terminals to allow for expansion of the capacitor in the event of failure.
- The maximum case temperature for oil-filled capacitors is 90°C.
(3) Ignitors (Starters):
- An ignitor is an electronic component that must be included in the circuitry of all high pressure sodium, low wattage metal halide (35W to 150W) and pulse start metal halide (175W to 1000W) lighting systems. The ignitor provides a pulse of at least 2500 volts peak to initiate the lamp arc.
- When the lighting system is energized, the ignitor provides the required high voltage pulse until the lamp arc is established and automatically stops pulsing once the lamp has started.
- It also furnishes the pulse continuously when the lamp has failed or the socket is empty.
- Ballasts that include an ignitor to start the HID lamp are limited in the distance they may be mounted remotely from the lamp because the ignitor pulse attenuates as the wire length between the ballast and lamp increases.
- For most of these ballast/ignitor combinations, the typical maximum ballast- to-lamp distance is listed in the Atlas as 2 feet. When this distance is exceeded the lamp may not start reliably and a long range ignitor is required.
- Some lighting applications require instant restarting of lamps after a momentary loss of power to the fixtures. When an HID lamp is hot after operation and power is removed and reapplied, it will not restart with a standard ignitor until the lamp sufficiently cools.
- When instant re strike of a hot lamp is required, a special ignitor is necessary that will provide a pulse with much greater peak voltage.
- Some ballast designs require ignitors to start the lamp. Ignitors create a glow discharge in the lamp by providing a voltage high enough to ionize the gas. This glow discharge is created by a 2500 volt pulse. Once the lamp is started, the ignitor stops pulsating automatically.
- Ignitors are designed to last thousands of hours. However, if the lamp has failed, or if the socket is empty, the ignitor will continue pulsing. In these situations, it is important to replace the lamp or turn off the HID fixture to preserve the ignitor’s life.
- Standard Ignitors are supplied with all High Pressure Sodium, Pulse Arc, and Metal Halide ballast requiring ignitors. These ballasts are supplied with the appropriate external ignitor and are to be wired within two feet of the lamp. Sometimes the ignitors can be permanently attached to or built into the ballast.
- Long range Ignitors are used in situations where an ignitor must be mounted further from the lamp than is recommended for a standard ignitor. The maximum lamp to ignitor distance for these ignitors is 50 feet, which may vary depending on the type of lamp, ballast, fixture, and wiring.
- Instant Restrike Ignitors generate multiple pulses to restrike lamp arc without a cool down time, after a brief power interruption has extinguished it. This requires a special lamp and is still subject to warm-up time.
- Automatic Shutoff Ignitors will apply pulses for 10 to 12 minutes and then deactivate if a lamp arc cannot be initiated. This saves the on ignitor life because a standard ignitor will continue to pulse. Resetting the Automatic Shutoff ignitor is accomplished by momentarily interrupting the power to the ballast. They should not be used on unswitched circuits that cannot be reset.
- Shutoff Devices is an Ignitor Accessory that can be used to convert a Standard Ignitor into an Automatic Shutoff Ignitor. The catalog lists all the different Ignitors and accessories.
- It is important to note that ignitors are specifically designed to operate properly with specific ballasts and cannot be interchanged with other ignitors or different brands of ignitors and ballasts.
- The ignitor should always be mounted near the ballast but not on the ballast.
Installation & Testing of HID (High Intensity Discharge):
- Only the input to HID lighting systems is a sine wave. Once the voltage and current is processed through the ballast and lamp, it is changed and is no longer a perfect sine wave. As a result of this transformation, only TRUE RMS volt and amp meters will give proper readings.
- TRUE RMS clamp-on current meters are also available and are most convenient when reading lamp current.
- There are many brands of test meters available. Some indicate RMS and some indicate TRUE RMS on the meter. They are not the same. Only those that have TRUE RMS will read non-sinusoidal waveforms accurately. The RMS meters will give readings 10 to 20% low depending on the shape of the voltage or current waveform.
1) Normal End of Lamp Life
- Most fixtures fail to light properly due to lamps that have reached end of life. Normal end of life indications are low light output, failure to start or lamps cycling off and on these problems can be eliminated by replacing the lamp.
2) Supply Input Measurement:
- Measure the line voltage at input to the fixture to determine if the power supply conforms to the requirements of the lighting system. For constant wattage ballasts (CWA, CWI), the measured line voltage should be within ±10 % of the nameplate rating. For reactor (R) or high reactance (HX) ballasts, the line voltage should be within ±5 % of the nameplate rating.
- Check breakers, fixture fuses, photocells and switches when no voltage reading can be measured. High, low or variable voltage readings may be due to load fluctuations.
- The supply voltage should be measured with the defective fixture connected to the line and power applied to help determine possible voltage supply problems.
3) Open Circuit & Short Circuit Voltage:
- If the proper input voltage is measured, most HID fixture problems can be determined by measuring open circuit voltage and short circuit current.
a) Measuring Open Circuit Voltage
- To determine if the ballast is supplying proper starting voltage to the lamp, an open circuit voltage test is required. The proper test procedure is:
- (1) Measure input voltage (V1) to verify rated input voltage is being applied to the ballast.
- (2) If the ballast has an ignitor [HPS, low wattage MH (35W to 150W) or pulse start MH], the ignitor must be disconnected or disabled with a capacitor (1000 pF or larger) across the voltmeter input to protect the meter from the high voltage ignitor pulse.
- Some ballasts have an integral or built in ignitor. If you are not sure if an ignitor is used put a capacitor across the meter for all open circuit voltage measurements.
- (3) With the lamp out of the socket and the voltage applied to the ballast or the proper tap of the ballast with multiple voltage inputs, read the voltage (V2) between the lamp socket center pin and shell. Some lamp socket shells are split. Make sure connection is being made to the active part. Open circuit voltage must be measured with a TRUE RMS voltmeter to provide an accurate reading.
- (4) Constant wattage (CWA, CWI) ballasts have a capacitor in series with the lamp. If the capacitor is open there will be no open circuit voltage. Measure the voltage on both sides of the capacitor. If the voltage exists on the ballast side but not on the lamp side,
- Change the capacitor and re-measure the open circuit voltage at the lamp socket. If there is still no voltage disconnect the lamp socket from the ballast and measure open circuit voltage again. Once a voltage is measured test the lamp socket for shorts with an Ohm-meter or replace the lamp socket. An ohm-meter test is not conclusive as the test is at low voltage and the failure may be due to the open-circuit voltage.
b) Short Circuit Lamp Current Test
- Do not be concerned about momentarily shorting a magnetic HID ballast output. They will not instantly burn up. An HID ballast is designed to limit current at the specified value range.
- To assure that the ballast is delivering the proper current under lamp starting conditions, a measurement may be taken by connecting an ammeter between the lamp socket center pin and the socket shell with rated voltage applied to the ballast. If available, a lamp socket adapter may be used as described in the open circuit voltage test.
- (1) Energize ballast with proper rated input voltage.
- (2) Measure current with ammeter at A1 and A2 as shown in the diagram shown below.
- (3) Readings must be within test limits. A clamp-on TRUE RMS ammeter may also be used to perform this test by placing an 18 gauge wire between the lamp and common leads of the ballast. When using a clamp-on ammeter for this measurement, be certain the meter is not near the ballast magnetic field or any steel object that may affect the reading.
- The short circuit current test will also determine a defective capacitor in constant wattage circuits. A shorted capacitor will result in high short circuit current, while an open capacitor or low value capacitor will result in no or low short circuit current.
4) Capacitor Testing and Ballast Performance
- Disconnect the capacitor from the circuit and discharge it by shorting the terminals or wires together.
- Check the capacitor with an ohmmeter set to the highest resistance scale
- If the meter indicates a very low resistance then gradually increases, the capacitor does not require replacement.
- If the meter indicates a very high initial resistance that does not change, it is open and should be replaced
If the meter indicates a very low resistance that does not increase, the capacitor is shorted and should be replaced.
- The ohmmeter method of testing capacitors will only determine open or shorted capacitors. The capacitance value can be tested by many available portable TRUE RMS meters having that capability, though a test using a dedicated capacitance meter is more conclusive.
- The capacitance value will affect lamp performance of Constant Wattage ballasts in ways that cannot be determined by the ohmmeter method.
- A capacitor may look good visually, but should be tested for capacitance value or replaced.
- The capacitor in a reactor or high reactance ballast circuits will only affect the ballast power factor and not ballast operation.
- Capacitor failure in these circuits will cause line supply current changes possibly causing circuit breakers to activate or fixture fuse failures.
5) Ballast Continuity Checks
- Continuity of Primary Coil
1) Disconnect the ballast from power source and discharge the capacitor by shorting its terminals or wires together.
2) Check for continuity of ballast primary coil between the voltage input leads.
- Continuity of Secondary Coil
1) Disconnect the ballast from power source and discharge the capacitor by shorting its terminals or wires together.
2) Check for continuity of ballast secondary coil between lamp and common leads
6) Ignitor Testing
- Ignitors are used as a lamp starting aid with all high pressure sodium; low wattage metal halide and pulse start lamps.
- Measurement of the starting pulse characteristics of an ignitor is beyond the capability of instruments available in the field. In laboratory tests, an oscilloscope equipped with a high voltage probe is used to measure pulse height and width. In the field, some simple tests may be performed to determine if the ignitor is operable.
- It is first assumed that the lamp has already been replaced with a known operable lamp.
- Replace the ignitor with a known operable ignitor. If the lamp starts, the previous ignitor was either mis-wired or Inoperative.
- If the lamp does not light check the open circuit voltage and short circuit secondary current
7) Further Magnetic Ballast Checks
- Probable Causes of Inoperable Ballasts
- Normal ballast end-of-life failure
- Operating incorrect lamps. Use of higher or lower wattage lamps than rated for the ballast may cause premature ballast end-of-life.
- Overheating due to heat from the fixture or high ambient temperatures causing the ballast temperature to exceed the Specified temperature.
- Voltage surge from lightening or power source malfunction.
- Mis-wired, pinched or shorted wires.
- Shorted or open capacitor.
- Incorrect capacitor for the ballast.
- Capacitor not connected to the ballast correctly.
- Probable Causes of Shorted or Open Capacitors
1) Normal capacitor end-of-life failure.
2) Overheated due to heat in the fixture or ambient temperature.
3) Capacitor mounted too close to ballast.
4) Incorrect voltage or capacitor value for ballast.
5) Mechanical damage such as over-tightened capacitor clamp.
- Electronic HID Ballasts
- Electronic HID ballasts present special troubleshooting challenges. The previously discussed procedures cannot be used to test electronic HID circuits. Electronic integrated circuit control limits reliable testing that can be performed in the field.
- An energized electronic HID ballast will attempt lamp ignition by producing high voltage pulses for a specified time period, usually between 10 and 30 minutes. Consult the ballast label for specific times.
- Unlike magnetic HID ballasts, momentary shorting either output lead of an electronic HID ballast to ground or each other.
Fluorescent Ballast / Lamp Troubleshooting:
Lamps will not operate.
|Check if there is power to the fixture.|
|Be sure lamp is properly seated in socket.|
|Reseat or change starter (preheat only)|
|Check wiring connections.|
Slow or erratic Starting
|Check ground (fixture must be grounded for reliable starting)|
|Check ballast label for correct lamp.|
|Check wiring connections.|
|Check for low supply voltage.|
|Be sure lamp is properly seated in socket.|
|Tighten loose components.|
|Install ballasts of the proper sound rating.|
|Replace faulty ballast(s). Normal operation should resume.|
|Note: All fluorescent ballasts emit some noise|
Lamp flickering and or swirling
|New lamps with less than 100 hours of service can exhibit this|
|Lamp to cold|
|Improper fixture design or ballast application|
|High circuit voltage|
|Improper wiring or installation|
|Poor lamp maintenance|
|Incorrect type of lamps|
|Incorrect number of lamps|
|High ambient temperature|
HID Ballast / Lamp Troubleshooting
1) Normal End of Lamp Life
- Normal end of life is important to understand for troubleshooting. It occurs when the lamp has aged to the point that the arc can no longer be sustained. End of life can be induced prematurely when lamps are operated at improper voltages, temperatures and positions.
- Mercury and metal halide lamps tend to emit low light output at end of life and starting will become intermittent. There will also be significant blackening on the arc tube located at the center of the lamp. High pressure sodium lamps retain their light output at the end of life, however, starting becomes intermittent at first and then impossible.
- There will be some blackening on the end of the arc tube located in the center of the lamp.
- Verify average rated lamp life as published by the lamp manufacturer and compare it to the actual life of the lamps in the system. Remember that the average rated life is not the same as the minimum life expectancy. The average rated life means that for a population of lamps, the average lamp lasted this long. When a system of lamps installed at the same time reaches the average rated life, we can expect half of the population of lamps to have failed. It is always important to be aware of the operation of the system when evaluating lamp life. For example, is the system operated round the clock either intentionally or as the result of faulty controls?
2) Lamps Will Not Start
- Check to see if lamp is loose in the socket. Check for arcing (blackening) at the center contact button and retighten lamp until it is properly seated. Tightening too much may cause lamp breakage.
- Check to see if lamp has failed or is damaged. Visually inspect for loose, broken internal parts or broken bulb wall.
- Visually inspect for separation of the lamp base. Check for looseness or for significant discoloration of the bulb wall near the base.
- Test the lamp in an adjacent fixture that is operating properly.
- Check to assure that the voltage at the fixture is not too low.
- Check the nameplate rating for the ballast. The voltage should be within 5% for reactor and high reactance ballasts, and within 10% for all others
3) Lamp Cycling (starting and shutting off repeatedly)
- Lamp cycling is a common end of life failure mode for high pressure sodium lamps.
- Check the capacitor: Verify the capacitor has the correct microfarad (uF) value as specified on the ballast. Inspect the capacitor for a swollen or ruptured case. Disconnect the capacitor and discharge it by shorting across its terminals with a piece of insulated wire. Use an If the resistance starts low and gradually increases, the capacitor is good. Any other reading indicates either an open or short circuit condition and the capacitor is bad.
- Check the ballast: If it is an older system, it could be simply the normal end of ballast life. Replace the ballast, capacitor (if present) and ignitor (if present). If the ballast is located in an extremely high ambient temperature, it can overheat the ballast or other parts. Check for discoloration of the ballast or other parts. Also check for failed capacitor (see above).Check the ballast open circuit voltage.
4) Short Lamp Life
- Verify the correct ballast type and wattage, and correct capacitor value.
- Check the input voltage and verify that it does not exceed 10% ballast input voltage shown on the label.
- Inspect the capacitor for a swollen or ruptured case.
- Check the lamp specification for “base up” or “base down” position specifics. Use the specified lamp only in the current orientation.
- Replace with a known good lamp.
5) Fuses Blow or Circuit Breakers or Circuit Breakers Open On Lamp Start Up
- Overloaded Circuit – Rewire to accommodate starting current of lamp/ballast combination.
- High Momentary Transient Current – Can be caused by reactor or autotransformer ballasts which draw high initial currents. Use current protective devices incorporating time delay elements. If these fail, change ballast as its characteristics will affect lamp life.
5 Step Guide to Fault Finding in Reactor Type Circuits:
- If metal halide, disconnect neutral wire from ignitor.
- Check all electrical connections.
- Remove lamp.
- Check voltage at choke output is equal to mains.
- If no voltage, check the continuity of choke by measuring resistance against a known good choke. Depending upon wattage, this reading should be from 2-50Ω.
- If reading is infinity, choke is faulty. Replace.
- Check voltage at lamp holder. Must equal mains voltage.
- If OK, replace neutral wire in ignitor and replace lamp. If lamp does not fire – faulty ignitor. Replace.