Interview Questions in Electrical Engineering - Part - 45
What is the difference between a Choke and a Reactor?
WIRE – A metal conductor that carries electricity along its length
COIL – A structure consisting of something wound in a continuous series of loops
CHOKE – Struggle for breath; have insufficient oxygen intake; Wring the neck of.
REACTOR – An electrical device used to introduce reactance into a circuit.
FLUORESCENCE - GEORGE STOKES – IRISH scientist, from the University of Cambridge, who named the phenomenon "FLUORESCENCE" after fluorite, a mineral, many of whose samples glow strongly due to impurities.
In 1852, in his famous paper on the change of wavelength of light, he described the phenomenon of fluorescence, as exhibited by fluorspar and uranium, materials which he viewed as having the power to convert invisible ultra-violet radiation into radiation of longer wavelengths that are visible
FLUORITE is a colorful mineral, both invisible and ultraviolet light, and the stone has ornamental and lapidary uses.
THERMIONIC EMISSION – The emission of electrons from very hot substances.
FATHER OF FLUORESCENT LAMP
In the year 1926, EDMUND GERMER, [Germany, patented the fluorescent lamp] a German inventor was recognized as the
FATHER OF THE FLUORESCENT LAMP.
The idea of coating the tube of an arc lamp emitting the ultraviolet with fluorescing powder to transform UV into visible light led to the realization of arc discharge emitters with spectral quality competing with incandescent emitters.
Fluorescent lamps work by ionizing mercury vapor in a glass tube.
Glass tubes are usually filled with an inert gas (usually argon) at low pressure.
FLUORESCENT MATERIALS
Zinc Silicate – Green
Calcium Tungstate – Blue
Magnesium Tungstate – Blue white
Zinc Beryllium Silicate – Yellow white
Cadmium Silicate – Yellow pink
Cadmium Borate – Pink
CHOKE or BALLAST - A steel cored copper or aluminium is used to obtain a transient high voltage at the time of starting to initiate the electron movement.
GLOW STARTER - Current operated device - Bimetallic strips are normally open and enclosed in glass bulb - Mixture of Hydrogen and Helium is used to produce glow and it does not consume any power. A 0.05 micro farad capacitor is used to control the RADIO INTERFERENCE.
RADIO INTERFERENCE - Whenever a tube is operated, an arc is produced in the starter; a nearby antenna catches the signal and disturbance in the Radio or Television may be produced. This is called radio interference.
For minimizing this, a capacitor 0.05 micro-farad is connected across the strips of the starter. The capacitor gets charged to the arc, and radio interference is controlled.
REACTOR – Balancing Reactor, current limiting reactor, Filter Reactor, Neutral Earthing Reactor, Parallel Reactor, Shunt Reactor, Smoothing Reactor, Split Reactor, Starting Reactor and Thyristor Controlled Reactor.
OPERATION –Generally, the reactance of the system under fault condition is low and fault currents may rise to a dangerously high value. If no steps are taken to limit the value of these short-circuit currents, not only will the duty required of circuit breakers be excessively heavy, but also damage to lines and other equipment will almost certainly occur.
CURRENT-LIMITING REACTORS are coils used to limit current during fault conditions. Such reactors have large values of inductive reactance and low-ohmic resistance.
AIR-CORED REACTORS -Dry-type and Oil immersed reactor
LOCATION OF REACTORS - In series with each generator, feeder and between busbar.
