Duo circuit

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Duo circuit

A duo connection is a parallel connection of an inductive and a capacitive fluorescent lamp branch. The inductive lamp branch consists of a conventional ballast and fluorescent lamp, the capacitive lamp circuit also has a capacitor that is connected in series with the ballast.

properties

This type of interconnection compensates for the reactive power ( series compensation ), because the capacitor ideally has exactly the capacity that the amounts of the reactive powers of the two branches are equal. This also reduces the stroboscopic effect of the lighting , as the phase shift of the currents in the individual branches of 90 ° to one another means that the light-dark phases of the lamps are also out of phase with one another. One lamp lights up exactly when the other goes out when the current crosses zero.

Capacitor characteristics

Compared to parallel compensation, series compensation places increased demands on the capacitor:

  • Dielectric strength up to 450 V.
  • tight tolerance of capacity (previously 4%, later 2%)

The size of the capacitor should have the value indicated on the choke. With a lamp current of 0.43 A, the required capacity is approximately 3.2 µF for a 36 W fluorescent lamp (or a 2 × 18 W tandem circuit) and approximately 3.2 µF for a 58 W fluorescent lamp (operating current 0.67 A) 5 µF. A disadvantage is the lower preheating power of the lamp cathodes, since the non-linearly increased current due to the beginning of the saturation of the iron core of the choke does not apply when the series-compensated branch is started. The series capacitor is therefore often chosen to be somewhat larger than required, which has a negative effect on the efficiency and the service life of the lamp. However, this can be avoided with electronic starters , which is why the correct capacity can then be used.

Advantages and disadvantages

The series compensation has the following advantages over the parallel compensation:

Others

The duo circuit is often confused with the tandem circuit , in which two fluorescent tubes are operated in series on one ballast. The tandem connection can, however, also be series-compensated, so that a luminaire with, for example, four fluorescent lamps T18, two of which form the capacitive branch, has the same advantages as a duo connection of two tubes.

literature

  • Günter Springer: Expertise in electrical engineering . 18th edition. Europa-Lehrmittel, Wuppertal 1989, ISBN 3-8085-3018-9 .

Web links

Individual evidence

  1. ↑ https://www.elektropraktiker.de/ep-2003-11-870-875.pdf?eID=tx_nawsecuredl&falId=6465&hash=9581058eff351d9248bd2eeda78fcaa2 S. Fassbinder: Reactive power compensation for fluorescent lamps , magazine Elektropraktiker, volume 11 (2003) , Page 872, accessed Nov. 12, 2017
  2. ↑ http://www.frako.com/fileadmin/pdf/Downloads/Handbuch/95-00135_11_13_9066_ Handbuch_blk.pdf Peter Riese: Handbook of reactive power compensation , page 15, accessed on November 12, 2017
  3. ↑ http://new.abb.com/docs/librariesprovider30/abb-stotz-kontakt-striebel-john-vertriebsgesellschaft-mbh/druckschrift-uchten21274C1FFA399DD615A640F0.pdf?sfvrsn=2 ABB company : Technical data control gear for lighting technology, page 8 , accessed on Nov. 12, 2017
  4. ↑ a b c https://www.kupferinstitut.de/fileadmin/user_upload/kupferinstitut.de/de/Documents/Shop/Verlag/Downloads/Anendung/Elektrotechnik/s180a.pdf S. Fassbinder: Optimal selection and mode of operation of ballasts for Fluorescent lamps / reactive power compensation for fluorescent lamps , page 12ff:, accessed on November 12, 2017