On 8/13/2013 6:38 AM, Tomsic wrote:
wrote in message
eb.com...
On 8/11/2013 1:04 PM, Tomsic wrote:
"Nate wrote in message
...
On 8/9/2013 5:44 PM, Tomsic wrote:

Big snip...


The screw-in LED bulbs incorporate some of the best LED engineering
around
because getting rid of the heat becomes especially hard when the LED
bulb
design is restricted to the size and shape of a standard light bulb.

I'm disappointed that Philips didn't put their marketing (and pricing)
strengths behind the L-Prize lamp. It has great performance specs,
particularly color, and the DOE life tests (200 samples) are now at
more
than 25,000 hours with no failures, no drop in light output and no
significant change in color.

Tomsic



it was available in Home Depot stores for $15 in subsidized areas for a
couple months. Unfortunately I found out about this shortly before they
disappeared. I bought six, the really frustrating thing is I seem to
have
lost the two that I didn't install into light fixtures immediately!

I've found only two possible drawbacks to them

1) some may not like the sub-3000K color temp, but that was part of the
L-prize requirements, so don't blame Philips for playing by the rules.

2) poor power factor

other than that, they're really nice and demonstrably superior to
comparable CFLs in every way save purchase price.

nate

I understand the need for high power factors in commercial/industrial
systems; but why in residential systems where there are such mixed loads
and
a power transformer for every few houses. Seems like the cost of adding
power factor correction in an LED bulb ought to be equated somehow with
the
need to do it.

Tomsic

Lower power factor causes losses (higher current through wire resistance)
for a utility and generators have to have a higher rating. The European
Union requires power factor correction for some power supplies - I don't
know which.

The lower power factor CFLs and probably LEDs is the same as in power
supplies and is caused by distortion of the current waveform instead of
the phase displacement that motors cause.

Yes, I understand that and the added complexity of the distorted waveform so
that any power factor correction circuitry will have to be electronic rather
than a simple capacitor (or inductor in some cases). I'm wondering how
serious the problem really is in homes where loads are relatively small and
the pole transformer tends to isolate the local power factor problems from
the larger distribution system.

Does the transformer reduce distortion power factor?

I haven't seen any articles, studies, etc.
that report any numbers or claim that systems have been damaged by power
factor problems.


An article on the actual magnitude of the problem would be interesting.

The EU requires switch mode power supplies (like in computers) rated
over 75W have some power factor correction. That is about all I have seen.

I agree with you that it may not be practical, or useful, to correct
CFLs or LEDs. I believe CFLs use small switch mode power supplies. My
guess is that LEDs don't use filter capacitors that cause a lot of the
problem.