Re: Flourescent lamp -Wasting Power?

From: John Fields (jfields_at_austininstruments.com)
Date: 12/19/04 

Date: Sun, 19 Dec 2004 11:19:08 -0600

On Sun, 19 Dec 2004 16:47:42 GMT, "Ban" <bansuri@web.de> wrote:

>Jeff Wisnia wrote:
>> Today I encountered something that is either stupid design or I've
>> somehow missed the point.
>>
>> While out shopping last night I found some nice looking flourescent
>> torchiere lamps on sale at a very attractive price. They had the usual
>> pair of "circline" flourescent bulbs and a switch for three light
>> levels. I decided it was time to pick up a couple and get rid of the
>> ancient 300 watt halogen ones (Pre safety guard models even.) sitting
>> around in two spare bedrooms. I had creepy feelings about some
>> uninformed guest drying out damp clothing by hanging it over a lit
>> halogen and starting a holocoust.
>>
>> I got 'em home, assembled them and was pleased with the results.
>>
>> This morning I went to move one and noticed that even though it had
>> been off all night, the electronic ballast, which was located topside
>> in the center of the bulbs, was noticably warm. I put my hand over
>> the other lamp's ballast and it too was warm.
>>
>> I took one down to my workshop and measured its current draw with the
>> lamp off. It was a bit over 9 watts. It appears that the ballast is
>> powered up continuously and there's a couple of control lines which
>> get diddled by the switch on the lamp's column to make the bulbs turn
>> on.
>> I've got a couple of other flourescent torchiers in the house which
>> switch line power ahead of the ballast as I'd expect.
>>
>> As we're paying close to 10 cents a KWH for electricity these days,
>> I'm not amused by the thought of paying around $15 a year for the
>> priviledge of keeping those two "energy saving" lamps plugged in, nor
>> do I want to go to the bother of unplugging them when they're not
>> going to be used or installing and wiring wall switches to control
>> the outlets they are plugged into.
>>
>> Those stupid lamps were returned to the store today, I'll go get ones
>> next week which don't waste my money when they aren't in use.
>>
>> Am I missing a reason why those lamps were designed that way other
>> than it may have enabled the manufacturer to save a few pennies on
>> each one?
>
>If the lamps would use 9W they would be *very* hot, I suspect the most
>current is not "real" in phase with the voltage, but imaginary as some
>capacitive or inductive load. I would guess 1-2W as you descibe it, much
>like the small low voltage xformers when idle. You cannot measure the power
>consumption with an amperemeter, even if it is true rms, but you need a
>dedicated power meter for it with 3connections at least. 

---
You can do it with an oscilloscope and a resistive shunt to measure
the current.  Display voltage on one channel, current on the other,
determine the phase angle between them and then P = IE cos(phi).
You could also do it with a current transformer once you've determined
its primary-to-secondary phase shift.
   
-- 
John Fields

Relevant Pages

  • Re: Metal Halide Lamps
    ... efficacy of metal halide lamps. ... Commercial linear inductor ballast ... function of power, I had the lab operate the lamp on the ...
    (sci.engr.lighting)
  • Re: Metal Halide Lamps
    ... efficacy of metal halide lamps. ... Commercial linear inductor ballast ... function of power, I had the lab operate the lamp on the ...
    (sci.engr.lighting)
  • Re: How much power registered at meter?
    ... reactive power, only real power drawn. ... I want to install a two 4' T8 tube fixture. ... loss in the electronic ballast. ... most 32-watt electronic ballasts run the lamps at ...
    (sci.engr.lighting)
  • Re: Philips and Sylvania F32T8 having different power usage
    ... Philips lamps are swapped in place of Sylvania lamps. ... the Philips lamps consistently cause the system to draw more power. ... use the same ballast, not just the same ballast type. ...
    (sci.engr.lighting)
  • Re: Flourescent lamp -Wasting Power?
    ... Jeff Wisnia wrote: ... > Today I encountered something that is either stupid design or I've ... > torchiere lamps on sale at a very attractive price. ... > lamp's ballast and it too was warm. ...
    (sci.electronics.design)