With primer and reactance
It is an operating system that is falling into disuse since the appearance of electronic devices that perform the same function in a better way and with less energy consumption. It is described, however, because many luminaires of this type still exist and will continue to exist for quite some time, although new ones are rarely installed now. The European Union, promoting energy savings, requires that the ballasts of these luminaires be more efficient every day, and that can only be achieved with electronic ballasts. Regulation (EC) No. 245/2009 of the commission of March 18, 2009 provided for the total prohibition of this type of ballast, and even some of the less efficient electronic ones, starting in 2017,[4] but in regulation 347/2010[5] it has limited said provision to the prohibition of the least efficient models.
In the figure above, apart from the lamp itself, two fundamental elements are distinguished: the "starter" (also called "starter" or "splitter") and the "reactance" or "ballast", which provides inductive reactance. In some Spanish-speaking countries its English synonyms starter and ballast are still used.
The primer, splitter or starter is formed by a small glass ampoule that contains gases at low pressure (neon, argon and mercury gas) and inside which there is a contact formed by a bimetallic sheet folded in a "U". In parallel with this contact there is a capacitor "Condenser (electrical)") intended for the double effect of acting as a spark absorber or spark arrester, and absorbing radio frequency radiation that could interfere with radio, TV or communications receivers. The presence of this capacitor is not essential for the operation of the fluorescent tube, but it helps a lot to increase the useful life of the contact of the bimetallic pair when it is subjected to work with high currents and high voltages. Both the starter and the luminaire shorten their useful life the more times they are turned on, for this reason it is recommended to use fluorescent lighting in continuous regimes and not as intermittent lighting.
The element that provides inductive reactance is called "ballast" or "ballast", although in some countries it is incorrectly called "reactance", which is actually the name of the electrical quantity it provides, not the element. Technically, it is a reactor that is made up of a coil of enameled copper wire, wound on a core of iron or electrical steel sheets. The term ballast should not be confused with its namesake, the material used in the construction of railroad tracks.
When the supply voltage is applied, the gases contained in the primer bulb are ionized, thereby increasing their temperature enough for the bimetallic sheet to deform, make contact, closing the circuit, which will cause the filaments "Filament (electricity)") at the ends of the tube to become red hot, and this begins the ionization of the gases in the vicinity of the filaments. When the contact closes, the primer turns off and its gases cool down again, so a couple of seconds later the contact opens again. This opening results in the magnetic field created in the inductive reactance abruptly disappearing, which results, in accordance with Faraday's law of induction,[6] in the generation of a high voltage peak (self-induction) that finishes ionizing the gases. A conductive plasma is formed inside the entire fluorescent tube and, therefore, a current of electrons passes through it that interacts with the Hg, Ar and Ne atoms, exciting them, which will emit light when de-excited, mainly in the ultraviolet (UV) region.
The potential difference applied to the filaments and the tube is pulsating, because the electrical voltage that powers the circuit is alternating current of 50 Hz (in Europe,...) or 60 Hz (in the USA, Japan,...). The filaments have thermal inertia, but the plasma does not, which produces a rapid flicker in the emitted light, which can bother some people, produce headaches and even seizures for those who suffer from epilepsy. This phenomenon is minimized by arranging the tubes in groups, each tube fed from different phases and with stroboscopic dispersion grids. This effect is eliminated with modern electronic ballasts.
The filaments, when heated, release electrons that, together with the self-induction peak, ionize the gases that fill the tube; A plasma "Plasma (state of matter)") is thus formed that conducts electricity. This plasma excites the mercury vapor atoms which, when de-excited, emit visible and ultraviolet light. These filaments are coated with a type of powder called TRIPLECARBONATE, this is used to promote the jump of electrons between the cathode and the anode and each time the fluorescent tube is energized, a small amount of the filament is released, which forms the black spot that is seen in the fluorescents when they are close to reaching their useful life. Once the triplecarbonate in the filaments has been exhausted, there is no way for the electron jump to occur and therefore the fluorescent tube leaves function, even though all other parts of the tube are in perfect condition. That is why the use of this technology is not recommended in places where it is constantly turned on and off.
The interior coating of the lamp has the function of filtering and converting ultraviolet light into visible light. The coloration of the light emitted by the lamp depends on the material of that internal coating. The tube material, common glass, helps reduce UV light that could escape outside the luminaire.
Fluorescent lamps are devices with a negative slope of their electrical resistance, with respect to the electrical voltage. This means that the greater the current that passes through them, the greater the degree of ionization of the gas and, therefore, the less resistance it opposes to the passage of said current. Thus, if the lamp is directly connected to a practically constant voltage source, such as that supplied by the electrical network, the intensity will tend to very high values, and the lamp will be destroyed in a few seconds. To avoid this, it is always connected through a current limiting element to keep it within its working limits. This limiting element, in the case of the installation in Figure 1, is the ballast that provides inductive reluctance, which will absorb the difference between the supply voltage and the working voltage of the tube.
Finally, the decrease in the internal resistance of the tube once it is turned on, makes the voltage between the terminals of the primer insufficient to ionize the gas contained in its ampoule and therefore the metallic contact remains inactive when the tube is on.
Until around 1975, electricity supply to homes through alternating current and direct current, both of 220 volts, coexisted in Argentina. Due to this, in this country a type of ballast for direct current was invented around 1950 that took advantage of the negative resistance of the ionized gases of the luminaire to generate an oscillation by relaxation of a frequency of a few kHz. The primer or starter effect was achieved with a noisy system of vibrating contacts that stopped as soon as the tube ignited. Its drawback was that the polarity had to be reversed from time to time so that the wear of the luminaire was the same on both filaments.
The fluorescent tube-ballast-primer assembly has reactive elements (coil and capacitors) that consume and give off reactive power respectively (the coil is consumed by the capacitors and given away). A capacitor is often sandwiched between the input terminals to allow the power factor of the device to be close to 1. This type of compensation is called "parallel compensation" because of this arrangement.
The following calculation allows us to know the value (in peak or nanofarads) of the capacitor that must be inserted, since if one with a value greater than necessary is placed, the current and its consumption will increase, so it is important to find the ideal one.
where:.
Example: If a tube is 18 W, with f = 50 Hz, V = 230 V (AC) and with final power factors of 0.85 and initial power factors of 0.226, the capacitor to be used must be 4 μF (microfarads).
With electronic ballast
There is currently another type of ballast or reactor, the electronic ballast, which consists of an electronic circuit and a small coil with a ferrite core "Ferrite (ferromagnetic ceramic)"). This ballast, unlike the inductive ballast, connects to the fluorescent without a starter and achieves instantaneous starts of the lamp and without noticeable flickering, or in other models, softer starts. In reality, it is not a reactor in the strict sense of the term, but rather an electronic circuit with semiconductors that generates:
Both processes add their effects to ionize the gases and thus produce the conductive plasma that will generate UV radiation. As a general rule, tubes that use electronic ballast have significantly higher lighting performance and a much longer average life than those that use inductive ballast.
Its connections are very simple:
As said at the beginning, the "phosphorus" mentioned in the drawing below is not the chemical element so called, but a chemical compound, which usually does not contain phosphorus.