Shop OBEX P1 Docs P2 Docs Learn Events
Correcting Power Factor of fluorescent lamps — Parallax Forums

Correcting Power Factor of fluorescent lamps

william chanwilliam chan Posts: 1,326
edited 2008-10-25 01:59 in General Discussion
Let's say I have a typical 36w 4 feet fluorescent light that uses 240v AC.
We all know that the coil ballast will skew the power factor one way which is not desirable.

Should I connect a X2 class capacitor across the power input lines (just before going into the lamp) to reduce the skew?
What should the capacitance value be? Will the correction be worth it?

Thanks.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
www.fd.com.my
www.mercedes.com.my

Comments

  • LeonLeon Posts: 7,620
    edited 2008-10-24 08:57
    I think it will only make a noticeable difference to your bill if you have lots of luminaires, as in an office building or factory. PF correction is then applied to the whole lot.

    Leon

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Amateur radio callsign: G1HSM
    Suzuki SV1000S motorcycle
  • TeslaTesla Posts: 55
    edited 2008-10-24 15:03
    I would not think so. PF only really comes into play in very high power loads because it make the peak amp higher without incease in power(current out of phase with voltage) which can cause undo heating of transformers and wires.

    36watt bulb no worries. Everything in your house for the most part sucks at PF. Most SMPS have a PF of .6 to .4. Shaded pole induction motors again .6 to .4
  • LeonLeon Posts: 7,620
    edited 2008-10-24 16:37
    The main reason for correcting for PF is to reduce electricity bills, it won't affect transformers and wires.

    Leon

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Amateur radio callsign: G1HSM
    Suzuki SV1000S motorcycle
  • william chanwilliam chan Posts: 1,326
    edited 2008-10-24 16:57
    I did not mention that this correction is going to be for house, office or factory.
    But I do know that if the PF for one 36w lamp can be corrected to 1 (or close to 1) using a built in capacitor,
    it will be useful when many such corrected lamps are installed at one location.
    Therefore, I am still interested to find out the optimum capacitance value for 1 lamp and whether the capacitor and coil ballast will oscillate as a LC pair.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    www.fd.com.my
    www.mercedes.com.my

    Post Edited (william chan) : 10/24/2008 5:21:33 PM GMT
  • LeonLeon Posts: 7,620
    edited 2008-10-24 17:45
    In a factory or office, it's cheaper to correct for all the luminaires (and other equipment) on a given phase than using capacitors.

    Leon

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Amateur radio callsign: G1HSM
    Suzuki SV1000S motorcycle
  • TeslaTesla Posts: 55
    edited 2008-10-24 23:25
    Power factor can cause undo heating in wires and transformers because of increase I2R losses. It is the diffrence between apparent power and real power. So if you have something that draws 120v at 10amps apparent power as measured with an amp clamp. Apparent power is 1200watts. If it had a PF of 0.5 then its real power, as measured with a power meter(not multi-tester) would be only 600watts of power. So this extra current that is not doing any work(because some of it out of phase with voltage) is causing I2R losses in the wires and the resistance of the transformer.
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2008-10-25 01:59
    Tesla is absolutely correct.

    Here are a couple of links that might help explain PFC

    www1.eere.energy.gov/industry/bestpractices/pdfs/mc60405.pdf
    www.allaboutcircuits.com/vol_2/chpt_11/4.html

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
Sign In or Register to comment.