[LINK] power and saving devices -- are you sure?

David Lochrin dlochrin at d2.net.au
Sun Apr 12 16:21:38 AEST 2009

On Sunday 12 April 2009 12:16, Jan Whitaker wrote:
> Now EDN reports they [compact fluorescent lamps] may use more energy 
> than claimed due to their poor power factor. Mike Grather, of Lumenaire 
> Testing Laboratory, 'checked the power factor for the CFLs and found 
> they ranged from .45 to .50.  Their "real" load was about twice that implied 
> by their wattage.' The good news: you're only billed for the 13 watts of 
> real power used. The bad news: the utilities have to generate the 
> equivalent of 28 watts (that is, 28 VA of apparent power for you EEs 
> out there) [...] 

I discovered only recently that modern fluorescent tubes and CFLs both use an inbuilt electronic power supply running at >5 KHz (tubes) or >22 KHz (CFLs).  Since only about 1% of people can detect a flicker rate of 60 Hz, any remaining flicker problems should only be apparent with old tubes using ballast chokes (which of course operated at 50Hz).

But these power supplies do indeed have a power factor problem.  The Australian & NZ standard AS/NZS 4847.2-2008 (and also the British standard) requires a minimum power factor of 0.55 or 0.9 "for lamps claiming high PF" as of November 2009.  However suppliers have a choice of three "standards" and the third is an American voluntary code which only requires a minimum PF of 0.5.  The full story is available at http://www.energyrating.gov.au/cf2.html

I see there's a requirement for harmonics, too.

One for the Link Engineers...


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