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What does power factor mean for Flourescent lamps?



 
 
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  #1  
Old January 25th 08, 10:01 PM posted to uk.d-i-y
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Default What does power factor mean for Flourescent lamps?

I tested an old 20W osram fluurescent bulb with built in ballast and
it read 14W 0.75 power factor

A new compact 11W fluurescent bulb read 12-14W 1.00 power factor.

The old 20W bulb was noticeably brighter than the new compact.
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  #2  
Old January 25th 08, 10:33 PM posted to uk.d-i-y
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Default What does power factor mean for Flourescent lamps?

405 TD Estate wrote:

I tested an old 20W osram fluurescent bulb with built in ballast and
it read 14W 0.75 power factor


Many older CFLs will present a somewhat inductive load (as will most
linear strip lights). So the peak current will be phase shifted with
respect to the peak of the mains voltage.

How were you making your measurements? Some equipment will not be able
to make accurate measurements with non unity power factors.

A new compact 11W fluurescent bulb read 12-14W 1.00 power factor.


These days the CFLs are usually power factor corrected to be closer to
unity and look like a mostly resistive load.

The old 20W bulb was noticeably brighter than the new compact.


No surprises there then ;-)

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Cheers,

John.

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  #3  
Old January 25th 08, 11:30 PM posted to uk.d-i-y
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Default What does power factor mean for Flourescent lamps?

On Fri, 25 Jan 2008 21:01:42 UTC, 405 TD Estate
wrote:

I tested an old 20W osram fluurescent bulb with built in ballast and
it read 14W 0.75 power factor

A new compact 11W fluurescent bulb read 12-14W 1.00 power factor.

The old 20W bulb was noticeably brighter than the new compact.


Nothing to do with relative brightness; another poster has given more
details.

Nothing to do with the velocity of the flour, or whether it's self
raising, either! :-)
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  #4  
Old January 26th 08, 03:16 AM posted to uk.d-i-y
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Posts: 9,306
Default What does power factor mean for Flourescent lamps?

In article ,
405 TD Estate writes:
I tested an old 20W osram fluurescent bulb with built in ballast and
it read 14W 0.75 power factor


It means the power drawn (14W) is 0.75 times what you would think if
you simply measured the RMS current and multiplied by the RMS voltage.
So you need to size the wires and fuses as though it was an 18.67W
lamp, although you will only be charged for the 14W it really uses.

A new compact 11W fluurescent bulb read 12-14W 1.00 power factor.

The old 20W bulb was noticeably brighter than the new compact.


As already stated, this is nothing to do with power factor.

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Andrew Gabriel
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