Re: d-day

[nobody@xxxxxxxxxxxx (Dave Houston)]

Jeff, I'm not at all sure what you're referring to or how your "large
capacitor" or X10 compatibility is pertinent to whether or not CFLs have low
power factors but this is taken from the Wikipedia article on Power Factor.
You can find essentially the same analysis and numbers at several other web
sites having to do with SMPS design. And, people have posted Kill-A-Watt
measurements of CFL PFs here that were in the 0.61 area. I doubt that low
cost commodity producers of CFLs are going to voluntarily increase cost by
using active PF correction. If you read my original post on this, I said "if
uncorrected", most CFLs with will have low PF - what was unstated is that
most CFLs now use SMPS and will need PF correction - I did not say that all
CFLs must have low PF.

     http://en.wikipedia.org/wiki/Power_factor

<quote>
In circuits having only sinusoidal currents and voltages, the power factor
effect arises only from the difference in phase between the current and
voltage. This is narrowly known as "displacement power factor". The concept
can be generalized to a total, distortion, or true power factor where the
apparent power includes all harmonic components. This is of importance in
practical power systems which contain non-linear loads such as rectifiers,
some forms of electric lighting, electric arc furnaces, welding equipment,
switched-mode power supplies and other devices.

A particularly important example is the millions of personal computers that
typically incorporate switched-mode power supplies (SMPS) with rated output
power ranging from 250 W to 750 W. Historically, these very-low-cost power
supplies incorporated a simple full-wave rectifier that conducted only when
the mains instantaneous voltage exceeded the voltage on the input
capacitors. This leads to very high ratios of peak-to-average input current,
which also lead to a low distortion power factor and potentially serious
phase and neutral loading concerns.

Regulatory agencies such as the EU have set harmonic limits as a method of
improving power factor. Declining component cost has hastened acceptance and
implementation of two different methods. Normally, this is done by either
adding a series inductor (so-called passive PFC) or the addition of a boost
converter that forces a sinusoidal input (so-called active PFC). For
example, SMPS with passive PFC can achieve power factor of about 0.7-0.75,
SMPS with active PFC, up to 0.99, while SMPS without any power factor
correction has a power factor of only about 0.55-0.65.

To comply with current EU standard EN61000-3-2, all switched-mode power
supplies with output power more than 75 W must include passive PFC, at
least.

A typical multimeter will give incorrect results when attempting to measure
the AC current drawn by a non-sinusoidal load and then calculate the power
factor. A true RMS multimeter must be used to measure the actual RMS
currents and voltages (and therefore apparent power). To measure the real
power or reactive power, a wattmeter designed to properly work with
non-sinusoidal currents must be used.
</quote>

"Jeff Volp" <JeffVolp@xxxxxxx> wrote:

>My own observations parallel Marc's input.
>
>Early CFLs all had large bases.  I disassembled a couple over the years, and
>they had a rectifier feeding a large electrolytic capacitor directly at the
>AC power input.  Some of those early CFLs attenuated X10 signals, but I
>never saw them radiate noise in the X10 transmission window, which extends
>for 1mS after each zero crossing.  The early Philips "Earthlights" were
>totally compatible with X10 transmissions.  Unfortunately, ours are finally
>wearing out after about a decade of service.
>
>Many have reported problems with newer CFLs causing problems for X10
>transmission.  I wrote a report on several that radiate noise in the X10
>frequency band inside the X10 transmission window.  Those have much smaller
>bases.  While I have not yet disassembled one, it seems pretty obvious from
>the radiated noise that the switching converter is running over the entire
>waveform.  That also allows them to eliminate the large high-voltage
>electrolytic that dictated the size of the base.
>
>To jam the circuitry into smaller and smaller bases, it is impossible to
>include the large high-voltage electrolytic capacitors that result in the
>low power factor numbers.  The downside is that some of these newer units
>with high-frequency switching supplies radiate that switching noise back
>onto the powerline.
>
>Jeff


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