On Wednesday, 17 January 2018 04:55:22 UTC, Johnny B Good wrote:
On Tue, 16 Jan 2018 22:00:09 +0000, John Rumm wrote:

====snip====


There is a second significant advantage, in that the strips are
typically arranged into relatively high voltage chains such that they
can be be wired in sets of 4 directly across the mains with no need to
use dropper capacitors. Hence better reliability and less temperature
sensitive ageing.

I'm afraid that's most definitely untrue. The closer the 'filament'
drive voltage rating approaches the supply voltage, the greater their
sensitivity to supply voltage variations becomes in regard of their
forward voltage drop conductivity.

LEDs can't be driven directly from a constant voltage source without
risk of thermal runaway when being driven close to their operational
limits typical of GLS applications. They need some form of current
limiting whether a simple capacitive dropper that drops 30 to 70% of the
supply voltage or else a more sophisticated electronic ballast that
supplies a more tightly controlled constant current optimised for the
LEDs used in the filament strings or the COB array.

Since my commissioning tests on each new LED GLS lamp I've purchased
during the past 5 years or so have revealed a higher consumption than
that claimed for these lamps in every case, I've finally come to the
conclusion that it's a consequence of meeting a minimum Lumens output
(typically a 60W equivalent of 810Lm) at the bottom of the 220 to 240
volt mains voltage range when powered from a 240v UK supply.

The first of the latest "High Efficiency" 68LPW GLS "60W equivalent" LES
lamps bought from Asda about 5 years ago claimed a consumption wattage
rating of 12W. Testing revealed that it was actually taking 14W but I
wasn't bothered too much about that since it certainly provided far more
light output than the 20W CFL "60W equivalent" it replaced.

The only downside being that it was rather heavier than the replaced CFL
due to the use of a meaty well engineered finned heatsink which placed an
extra burden on the height adjustable pendant luminaire over the dining
table.

It was eventually replaced a year or two later with an even more
efficient (and lighter) 81LPW "60W equivalent" LED with a claimed
consumption of just 10W which measured pretty close to 12W. Again, the
extra consumption wasn't an issue (but I was beginning to see a pattern
emerging). The Asda branded lamp (part number: LDA12WE27COA3000K)[1]
landed up in my Anglepoise desk lamp where it remains to this day.
Interestingly, a recent test revealed a consumption figure of 13.5W which
most likely was the result of the voltage being lower this time round
compared to the original test voltage condition some 5 years ago.

More recently, I've seen the same sort of inflated measured consumption
versus the rated consumption with the Poundland lamps - 6W versus 5.5 for
the SBC 470Lm lamps and the later 510Lm versions. Even the three quid
Home & Bargain 12W 1500Lm (125LPW) LES "100W equivalent" showed an
inflated wattage reading of about 13.5W when I tested it before
installing it into the bathroom light fitting which had housed the last
remaining incandescent GLS lamp.

[1] Curiously, this Asda branded lamp quotes 50/60Hz in addition to the
220 to 240 volt supply @67mA (implying a PF of 0.85) which strongly
suggests an electronic ballast more sophisticated than a mere dropper
capacitor.

However, the 220 to 240 volt range seems to be more in keeping with UK
and European supply voltages where 50Hz is the standard frequency of
supply so it's just possible that the mention of 60Hz may simply be a
matter of mislabelling (possibly a "force of habit" error).

The only other place where 60Hz is standard outside of the USA that
comes to mind is Japan (well, roughly half of Japan - the other half does
use 50Hz) so it seems a little unusual that a lamp designed to operate in
the range of 220 to 240 should also include the 60Hz option.

Since ICBA to find a couple of 7AH SLAs to black start my spare APC
SmartUPS700 in 60Hz mode, this claim of 60Hz compatibility is going to
remain untested for the foreseeable future.

sounds like you're not up to date with the latest generation of LED lighting drivers. Not finding the link but basically they switch which LEDs are on according to the momentary mains voltage.


NT

That sounds like a terrible idea.

JR, JbG and even AG can argue the toss, but if Big Clive Mitchell
isn't aware of it, it's not happening. ;-)



--

Graham.
%Profound_observation%