Exploding CFLs

"Mauried" wrote

Ive had a number of these lamps literally explode.

Does anyone have a typical circuit of whats in the base of these lamps. Im guessing its some kind of electronic ballast,

**** If you are only guessing "it's some kind of electronic ballast",then even if someone supplied you with a circuit,you wouldn't have the foggiest idea of what you were looking at!

The mind boggles!

Brian g

"Mauried" schreef in bericht news: snipped-for-privacy@news.tpg.com.au...

Have a look at:

petrus bitbyter

"Mauried"

** There is a good chance that your "explosive " is a common, 400 volt DC, polyester film cap.

Wired right across the AC supply - but not rated for that job.

CFLs are not required to meet any performance or good design standards.

OTOH - are you in a lightning prone area ?????

This URL may prove informative:

....... Phil

Why, ballasts dont have to be electronic.

Thanks for this , a good informative article.

>

"Mauried"

** You don't have a problem with insects do you ?

Tiny cockies or ants maybe ?

Nice and warm inside a CFL....

...... Phil

Thats an ill informed statement They do in Australia and New Zealand and it was mentioned previously.

"Jonno" "Phil Allison"

** Shame it is total fact - you ass.

** Funny how this anonymous f****it did not point to it.

...... Phil

Good point,

I have found in the past that cockies conduct rectified mains (DC) extremely well, enough to cause violent fuse blowings (and sometimes semiconductor damage) in typical switchmode power supplies. I haven't been there when its actually happened, but looking at the resulting burn marks and cockroach remains, could possibly make quite a "bang" when it happened.

"kreed" "Phil Allison"

** Another likely cause for an exploding CFL is water ingress or condensation forming on the PCB inside. The CFL will then likely explode soon as it is switched on.

Incandescent lamps are all airtight sealed, for obvious reasons - but many CFLs have ventilation holes in the middle of the tube assembly that permit water to enter - OR and much more insidious, condensation to form inside if used in an outdoor situation like a porch or garden shed/ garage.

Some makers warn you against outdoor use on the pack, while others do not.

Some makers warn you about using them inside a sealed lamp fitting, others do not.

Looks like the public have to find out the HARD way every time.

....... Phil

this is a very plausible failure mechanism. Because all of the internal creepage & clearance is working, rather than safety, it is often frighteningly small. And for minimum cost, few are conformally coated.

Cheers Terry

"Terry Given"

** The ambiguous phrase "conformally coated " seems to mean whatever the user conveniently wants it to mean.

For a CFL's electronics to be made immune from water ingress or internal condensation, the PCB would have to be completely potted in a moisture proof material.

A spray coat of clear lacquer would not do.

Might be easier to just seal up those darn ventilation holes.

....... Phil

true. I have seen some reminiscent of CRC plasticote, and others ~ 3mm thick.

yep. but a hard potting material would be a bad choice, because of the inevitable thermal gradients.

nope.

something in-between those two extremes is probably workable. but its an extra, messy, step, and so adds cost. Therefore it aint likely to happen.

I suspect that the lifetime of the electronics would plummet if you did that. The electroytic(s) probably get quite a beating as is.

And of course if you seal up the holes, dT gives rise to dP. Still, at least they are physically small.

In pracitce I think the approach most CFL manufacturers seem to take (ignoring it) is probably cheapest overall for them. Shame about us poor consumers :(

to be fair all the CFL failures I have had (perhaps 6 in 3 years, out of about 30 CFLs) have been first-power-up failures, rather than very short lifetimes. Which suggests crappy manufacturing . Which is what we can expect from made-in-china-as-cheaply-as-possible stuff.

This has been an interesting thread. I especially liked the link. Cheers Terry

OK that rules out the other 1% then :-)

MrT.

Maybe you should give us a link to it then, *if* you can?

MrT.

"Mr.T" "Jonno"

** He gave a link to a NZ Electricity Commission discussion paper.

Shame there is nothing mandatory about the performance standards it mentions.

...... Phil

I did and if you didnt read it find it yourself. Here are the standards. AS/NZs60968 2001 Google it like I did, if you can.

standards.

Can you point out the compulsory *performance* standards part that is currently enforceable by law in Australia, or are you just confusing safety standards? (which seem to be little enforced here anyway)

MrT.