Metalized polypropylene film capacitors for discharge lamps|
The so-called fluorescent lamps are discharge lamps available in a number of standards types:
Metal vapour lamps (mercury-sodium)
Metal Halide lamps.
These lamps require a reactor or Ballast, which keeps the current of the electric arc costant, according to the pre-set value. The reactor, being an inductive load, causes an increase of the reactive current with a strong reduction of the power factor, with values even lower than cos 0.5. To bring the power factor back as provided for by the law, it is necessary to connect a suitable capacitor to the feeding circuit. This can be done with two different wiring methods:
SERIES CONNECTION: recommended above all circuits with double lamps, but not used much nowadays. It requires the series connection of the capacitor to the mains;
PARALLEL CONNECTION: it requires the shunt connection to the mains and the parallel connection to the lamp - reactor unit.