Connect with us

cfl's , poor Power Factor and your power meter

Discussion in 'Hobby Electronics' started by tuppy, Apr 10, 2009.

Scroll to continue with content
  1. tuppy

    tuppy Guest

    With all the fuss over powerfactor correction (or lack of) with CFL
    lamps and with some cfls with poor powerfactor (like 0.4) the actual
    power usage can be double the stated Watt rating.
    I didn't really care as my powermeter measures Kilowatts , ie its not
    a VA meter but doing a little more reasearch I realise we are paying
    for the poor power factor. What a scam!

    Take a look at your power meter; I think it measures apparent power
    thought its actually called KWH meter that is contradictory to one
    another KVAH meter is apparent power while KWH is real power, if you
    look upon the construction of the meter itself it acts like a simple
    induction motor running both is current and in voltage, the line
    current is usually the total current you use in your household, P=VA ,
    this is actually the formula for apparent power in an AC circuits,
    because P=VA X power factor is the formula for real power in AC
    circuits and I don't see any provisions of power factor reading in the
    KWH meter that makes me conclude that indeed the meter used in our
    homes measures apparent power not real power. :) though it states KWH
    meter on the nameplate.
  2. Phil Allison

    Phil Allison Guest

    "tuppy the troll "
    ** Inrush surge is a FAR bigger issue with CFLs than the distorted current
    wave issue.

    ** Utter BOLLOCKS !!

    The stated power consumption in watts for CFLs IS the REAL power

    ** More BOLLOCKS.

    Domestic power meters ARE watt meters.

    ** Totally false.

    ...... Phil
  3. Davo

    Davo Guest

    From Wiki

    Electromechanical meters
    The most common type of electricity meter is the Thomson or
    electromechanical induction watt-hour meter, invented by Elihu Thomson
    in 1888.
    The electromechanical induction meter operates by counting the
    evolutions of an aluminium disc which is made to rotate at a speed
    proportional to the power. The number of revolutions is thus
    proportional to the energy usage. It consumes a small amount of power,
    typically around 2 watts.
    The metallic disc is acted upon by two coils. One coil is connected in
    such a way that it produces a magnetic flux in proportion to the voltage
    and the other produces a magnetic flux in proportion to the current. The
    field of the voltage coil is delayed by 90 degrees using a lag coil.
    [1]This produces eddy currents in the disc and the effect is such that a
    force is exerted on the disc in proportion to the product of the
    instantaneous current and voltage. A permanent magnet exerts an opposing
    force proportional to the speed of rotation of the disc - this acts as a
    brake which causes the disc to stop spinning when power stops being
    drawn rather than allowing it to spin faster and faster. This causes the
    disc to rotate at a speed proportional to the power being used.

    From me

    So the meter has two coils, one for voltage and one for current.
    Try putting some big inductors or capacitors on your circuit as a load,
    what does the power meter do?
  4. Eeyore

    Eeyore Guest

    Fundamental misunderstanding of physics. The VA usage (apparent power) may
    be higher but NOT the actual power.

  5. Franc Zabkar

    Franc Zabkar Guest

    From Energy Australia:

    .... most residential classification customers are metered by a
    spinning disc meter, or a basic electronic meter which does not have
    enough "smarts" in the meter device to enable billing to be carried
    out at a KVA pricing.

    Currently small customers are billed on KWh pricing, and KVA Demand
    pricing usually relates to large commercial and industrial
    installations where poor power factor may impact upon the EA network

    - Franc Zabkar
  6. tuppy

    tuppy Guest

    thanks Franc,

    looks like I dont have to worry about paying for powerfactor.

    thanks again for good answer.
  7. Pete

    Pete Guest

    ... most residential classification customers are metered by a
    That part is phrased interestingly - does it mean that if we get
    "non-basic" electronic meters, that they'll start KVA pricing?

    I think I remember hearing that we're all going to get new electronic
    meters in Victoria in the medium term. I wonder what type of meters?

Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day