"Choke ballast" (inductor) used in older lighting. This example is from a tanning bed. Requires a lamp starter (below) and capacitor.

Lamp starter, required with some inductor type ballasts. Connects both ends of the lamp together to "preheat" the lamp ends for 1 second before lighting.

An electrical ballast (sometimes called control gear) is a device intended to limit the amount of current in an electric circuit. Electric current is the flow (movement of Electric charge. The SI unit of electric current is the Ampere.

Ballasts vary greatly in complexity. They can be as simple as a series resistor as commonly used with small neon lamps. |- align = "center"| |width = "25"| | |- align = "center"| || Potentiometer |- align = "center"| | | |- align = "center"| Resistor| | A neon lamp is a Gas discharge Lamp containing primarily Neon gas at low Pressure. For higher-power installations, too much energy would be wasted in a resistive ballast, so alternatives are used that depend upon the reactance of inductors, capacitors, or both. An inductor is a passive electrical component designed to provide Inductance in a circuit A capacitor is a passive electrical component that can store Energy in the Electric field between a pair of conductors Finally, ballasts can be as complex as the computerized, remote-controlled electronic ballasts used with fluorescent lamps. A fluorescent lamp or fluorescent tube is a Gas-discharge lamp that uses Electricity to excite mercury Vapor.

Necessity for current limiting

Ballasts are used where a load does not regulate its own current consumption well enough. These are most often used when an electrical circuit or device presents a negative (differential) resistance to the supply. Negative resistance (or negative differential resistance (NDR or differential negative resistance (DNR is a property of Electrical circuit elements composed If such a device were connected to a constant-voltage power supply, it would draw an increasing amount of current until it was destroyed or caused the power supply to fail. Electrical tension (or voltage after its SI unit, the Volt) is the difference of electrical potential between two points of an electrical To prevent this, a ballast provides a positive resistance or reactance that limits the ultimate current to an appropriate level. Electrical resistance is a ratio of the degree to which an object opposes an Electric current through it measured in Ohms Its reciprocal quantity is In this way, the 'ballast' provides for the proper operation of the negative resistance device by appearing to be a legitimate, stable resistance in the circuit.

Examples of such negative-resistance devices are gas-discharge lamps. Gas discharge lamps are a family of artificial light sources that generate light by sending an Electrical discharge through an ionized gas i

Ballasts can also be used simply to deliberately reduce the current in an ordinary, positive-resistance circuit.

Prior to the advent of solid-state ignition, automobile ignition systems commonly included a ballast resistor to regulate the voltage applied to the ignition system. An ignition system is a system for igniting a fuel-air mixture

Although LEDs are positive resistance devices, they have insufficient resistance to regulate their current consumption when operated from a voltage controlled source, so ballasts are used to control the current flow through the LED. Because the power dissipation is minuscule, simple resistor ballasts are normally used.

Resistors

The term ballast resistor primarily refers to a resistor which compensates for normal or incidental changes in the physical state of a system. |- align = "center"| |width = "25"| | |- align = "center"| || Potentiometer |- align = "center"| | | |- align = "center"| Resistor| | It may be a fixed or variable resistor.

Fixed resistors

For simple, low-powered loads such as a neon lamp or LED, a fixed resistor is commonly used. Because the resistance of the ballast resistor is large it dominates the current in the circuit, even in the face of negative resistance introduced by the neon lamp. Negative resistance (or negative differential resistance (NDR or differential negative resistance (DNR is a property of Electrical circuit elements composed

The term also refers to an automobile engine component that lowers the supply voltage to the ignition system after the engine has been started. The internal combustion engine is an engine in which the Combustion of Fuel and an Oxidizer (typically air occurs in a confined space called a Electrical tension (or voltage after its SI unit, the Volt) is the difference of electrical potential between two points of an electrical An ignition system is a system for igniting a fuel-air mixture Because cranking the engine causes a very heavy load on the battery, the system voltage can drop quite low during cranking. In electronics a battery is a combination of two or more Electrochemical cells which store chemical Energy which can be converted into electrical energy To allow the engine to start, the ignition system must be designed to operate on this lower voltage. But once cranking is completed, the normal operating voltage is regained; this voltage would overload the ignition system. To avoid this problem, a ballast resistor is inserted in series with the supply voltage feeding the ignition system. Occasionally, this ballast resistor will fail and the classic symptom of this failure is that the engine runs while being cranked (while the resistor is bypassed) but stalls immediately when cranking ceases (and the resistor is re-connected in the circuit).

Modern electronic ignition systems do not require a ballast resistor as they are flexible enough to operate on the low cranking voltage or the ordinary operating voltage.

In some old AC/DC receivers (universal sets), the vacuum tube heaters are connected in series. The All American Five was a mass-produced superheterodyne Radio receiver with five Vacuum tubes first designed and produced in the USA in the This article is about the electronic device not an evacuated pipe used for experiments in Free-fall. Since the voltage drop across all the filaments in series is sometimes less than the full mains voltage, it was often necessary to get rid of the excess voltage. A ballast resistor was often used for this purpose, as it was cheap and worked with both ac and dc.

Self-variable resistors

Some ballast resistors have the property of increasing in resistance as current through them increases, and decreasing in resistance as current decreases. Electrical resistance is a ratio of the degree to which an object opposes an Electric current through it measured in Ohms Its reciprocal quantity is Physically, some such devices are often built quite like incandescent lamps. The incandescent light bulb, incandescent lamp or incandescent light globe is a source of electric Light that works by Incandescence, (a general Like the tungsten filament of an ordinary incandescent lamp, if current increases, the ballast resistor gets hotter, its resistance goes up, and its voltage drop increases. Tungsten (ˈtʌŋstən also known as wolfram (/ˈwʊlfrəm/ is a Chemical element that has the symbol W and Atomic number 74 Electric current is the flow (movement of Electric charge. The SI unit of electric current is the Ampere. If current decreases, the ballast resistor gets colder, its resistance drops, and the voltage drop decreases. Electric current is the flow (movement of Electric charge. The SI unit of electric current is the Ampere. Voltage drop is the reduction in Voltage in an Electrical circuit between the source and load Therefore the ballast resistor reduces variations in current, despite variations in applied voltage or changes in the rest of an electric circuit. These devices are sometimes termed barretters. The hot wire barretter was a demodulating detector invented in 1902 by Reginald Fessenden that found limited use in early Radio receivers In effect it was

This property can lead to more precise current control than merely choosing an appropriate fixed resistor. The power lost in the resistive ballast is also reduced because a smaller portion of the overall power is dropped in the ballast compared to what might be required with a fixed resistor.

In times past, household clothes dryers sometimes incorporated a germicidal lamp in series with an ordinary incandescent lamp; the incandescent lamp operated as the ballast for the germicidal lamp. A clothes dryer or tumble dryer is a household appliance that is used to remove the moisture from a load of Clothing and other Textiles, generally A germicidal lamp is a special type of lamp which produces Ultraviolet light (UVC A commonly used light in the home in the 1960s in 220-240V countries was a circleline tube ballasted by an under-run regular mains filament lamp. Self ballasted mercury-vapor lamps incorporate ordinary tungsten filaments within the overall envelope of the lamp to act as the ballast, and it supplements the otherwise lacking red area of the light spectrum produced.

Reactive ballasts

Several typical magnetic ballasts for fluorescent lamps. A fluorescent lamp or fluorescent tube is a Gas-discharge lamp that uses Electricity to excite mercury Vapor. The top is a high-power factor, lead-lag ballast for two 30-40W lamps. The middle is a low power factor ballast for a single 30-40W lamp while the bottom ballast is a simple inductor used with a 15W preheat lamp.

Because of the power that would be lost, resistors are not used as ballasts for lamps of more than about two watts. Instead, a reactance is used. In an ideal or theoretically perfect reactance, no power would be lost while limiting the current; realistically, losses due to resistance can only be minimized, not eliminated entirely.

An inductor is very common in line-frequency ballasts to provide the proper starting and operating electrical condition to power a fluorescent lamp, neon lamp, or high intensity discharge (HID) lamp. An inductor is a passive electrical component designed to provide Inductance in a circuit A fluorescent lamp or fluorescent tube is a Gas-discharge lamp that uses Electricity to excite mercury Vapor. A neon lamp is a Gas discharge Lamp containing primarily Neon gas at low Pressure. A High-intensity discharge (HID lamp is a type of electrical lamp which produces light by means of an electric arc between Tungsten Electrodes (Because of the use of the inductor, such ballasts are usually called magnetic ballasts. ) The inductor has two benefits:

1. Its reactance limits the power available to the lamp with only minimal power losses in the inductor
2. The voltage spike produced when current through the inductor is rapidly interrupted is used in some circuits to first strike the arc in the lamp. In electrical engineering spikes are fast short duration electrical transients in voltage ( voltage spikes) current ( current spike) or transferred energy

A disadvantage of the inductor is that current is shifted out of phase with the voltage, producing a poor power factor. The power factor of an AC electric power system is defined as the Ratio of the real power to the apparent power, and is a number between 0 and In more expensive ballasts, a capacitor is often paired with the inductor to correct the power factor. A capacitor is a passive electrical component that can store Energy in the Electric field between a pair of conductors In ballasts that control two or more lamps, line-frequency ballasts commonly use different phase relationships between the multiple lamps. This not only mitigates the flicker of the individual lamps, it also helps maintain a high power factor. These ballasts are often called lead-lag ballasts because the current in one lamp leads the mains phase and the current in the other lamp lags the mains phase.

In most parts of the world, the mains voltage is sufficient to strike and maintain an arc in the lamp. In the USA, the mains voltage is not sufficient for the larger lamps so an autotransformer is used to step up the voltage. The United States of America —commonly referred to as the An autotransformer (sometimes called autoformer) is an electrical Transformer with only one winding. The autotransformer is designed with enough leakage inductance so that the current is appropriately limited. Leakage inductance is that property of an electrical Transformer that causes a winding to appear to have some inductance in series with the mutually-coupled

Because of the large inductors and capacitors that must be used, reactive ballasts operated at line frequency tend to be large and heavy. They commonly also produce acoustic noise (line-frequency hum). is a one volume manga created by Tsutomu Nihei as a prequel to his ten-volume work Blame!.

Prior to 1980 in the United States, PCB-based oils were used as dielectric in the capacitors contained in many ballasts (see transformer oil). Polychlorinated biphenyls ( PCB s are a class of Organic compounds with 1 to 10 Chlorine atoms attached to Biphenyl which is a molecule composed Transformer oil is usually a highly- refined Mineral oil that is stable at high temperatures and has excellent electrical insulating properties

Fluorescent lighting practices and terminology differ between USA and Europe, and some of this section does not currently apply worldwide.

Electronic ballasts

Electronic ballast of a compact fluorescent lamp

An electronic lamp ballast uses solid state electronic circuitry to provide the proper starting and operating electrical condition to power one or more fluorescent lamps and more recently HID lamps. Solid-state Electronic components devices and systems are based entirely on the Semiconductor, such as Transistors Microprocessor chips and An electronic circuit is a closed path formed by the interconnection of Electronic components through which an Electric current can flow A High-intensity discharge (HID lamp is a type of electrical lamp which produces light by means of an electric arc between Tungsten Electrodes Electronic ballasts usually change the frequency of the power from the standard mains (e. g. , 60 Hz in U. S. ) frequency to 20,000 Hz or higher, substantially eliminating the stroboscopic effect of flicker (100 or 120 Hz, twice the line frequency) associated with fluorescent lighting (see photosensitive epilepsy). Temporal aliasing is the term applied to a visual Phenomenon also known as the stroboscopic effect. Photosensitive epilepsy is a form of Epilepsy in which Seizures are triggered by visual stimuli that form patterns in time or space such as flashing lights bold In addition, because more gas remains ionized in the arc stream, the lamps actually operate at about 9% higher efficacy above approximately 10 kHz. Lamp efficacy increases sharply at about 10 kHz and continues to improve until approximately 20 kHz. ^[1] Because of the higher efficiency of the ballast itself and the improvement of lamp efficacy by operating at a higher frequency electronic ballasts offer higher system efficacy. In addition, the higher operating frequency means that it is often practical to use a capacitor as the current-limiting reactance rather than the inductor required at line frequencies. Capacitors tend to be much lower in loss than inductors, allowing them to more closely approach an "ideal reactance".

Electronic ballasts are often based on the SMPS topology, first rectifying the input power and then chopping it at a high frequency. A switched-mode power supply, switching-mode power supply or SMPS, is an electronic Power supply unit (PSU that incorporates a switching regulator Advanced electronic ballasts may allow dimming via pulse-width modulation and remote control and monitoring via networks such as LonWorks, DALI, DMX-512, DSI or simple analog control using a 0-10V DC brightness control signal. Pulse-width modulation (PWM of a signal or power source involves the Modulation of its Duty cycle, to either convey information over a LonWorks is a networking platform specifically created to address the unique performance reliability installation and maintenance needs of Control applications The platform The Digital Addressable Lighting Interface ( DALI) is a Digital protocol for the controlling of Lighting in buildings such as Electrical DMX512-A is an EIA-485 based Communications protocol that is most commonly used to control Stage lighting and effects Digital Signal Interface ( DSI) is a protocol for the controlling of lighting in buildings (initially Electrical ballasts. Direct current ( DC) is the unidirectional flow of Electric charge.

Efficacy

Efficacy is the correct term and is the term used in this industry. Efficacy means "capacity or power to produce a desired effect" while "efficiency" refers to the ratio of power input vs power output. Since "lumen" is a measure of perceived light or the "desired effect" and not that of optical output of the lamp, term efficacy is used. A 60 W fluorescent lamp with red phosphor producing 30 W of optical power and the same power green phosphor lamp producing 30W of optical power would both have an efficiency of 50%, however the green lamp would have a higher efficacy due to the sensitivity of our eyes, as one watt of green light has greater luminous flux than one watt of red light. In photometry, luminous flux or luminous power is the measure of the perceived power of Light.

Two different fluorescent lamps of the same power could be giving off the same amount of photometric power within the visible spectrum, but could have different efficacy depending on the way it conforms to the way our eyes respond. The modern polychromatic lamps are designed on this concept. White light is made by blending individual color phosphors that matches the sensitivity of our eyes instead of emitting light in broad spectrum including where our eyes are not so sensitive.

Instant start

Starts lamps without heating the cathodes at all by using a high voltage (around 600 V). It is the most energy efficient type, but gives the least number of starts from a lamp as emissive oxides are blasted from the cold cathode surfaces each time the lamp is started. This is the best type for installations where lamps are not turned on and off very often.

Rapid start

Applies voltage and heats the cathodes simultaneously. Provides superior lamp life and more cycle life, but uses slightly more energy as the cathodes in each end of the lamp continue to consume heating power as the lamp operates.

Programmed start

More advanced version of rapid start. Applies power to the filaments first, then after a short delay to allow the cathodes to preheat, applies voltage to the lamps to strike an arc. Gives the best life and most starts from lamps. This is the preferred type of ballast for applications with very frequent power cycling such as vision examination rooms and restrooms with a motion detector switch.

References

http://www.worldwise.com/recfluorlig.html http://earth911.org/blog/2007/06/16/hazardous-fluorescent-lamp-ballasts/

See also

• Compact fluorescent lamp (CFL)
• Fluorescent lamp
• High-intensity discharge lamp (HID)
• Mercury-vapor lamp
• Neon lamp
• Sodium lamp

External links

• NEMA - National Electrical Manufacturers Association