movs catching fire

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Re: movs catching fire

Postby Sleepwalker3 » Sun Dec 23, 2012 9:48 am

@Matseng - Looks like 1/4W or 1/2W to me, they've been gradually increasing the Power Vs. Size ratio for a while, so much so that at work we had to change our system so that we wouldn't get one batch of older small wattage ones mixed up with higher wattage ones that looked near identical.

It's unfortunately all too common to see things like that and as most plain LED's have a PIV closer to something like 5V, it's just crazy. I had a powerboard that started smoking too years ago. It had one LED at the end and the resistor had started to cook and melt the plastic. Around here the voltage fairly commonly can creep over 250V, so it's not surprising. I think the resistor was something like a 1W, but I calculated the power it was dissipating and it was over it's rating. How these things get 'Safety Approvals' I'll never know. Likely the approvals are given out by pen pushing engineers who drive a desk and never get out and get their hands dirty in the real world.

@Skybeaver - I'll see what I can find. Unfortunately I end up with so much of that sort of junk I tend to just chuck a heap of it when there's a clean-up, but there's probably a few things around. Kind of wish now I'd taken more pics of all that sort of thing, but a lot of it would have been well before we were all walking around with hi-res phone cameras in our pockets.
Anybody else got in good spectacular failures?
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Re: movs catching fire

Postby matseng » Sun Dec 23, 2012 10:08 am

Sleepwalker3 wrote:@Matseng - Looks like 1/4W or 1/2W to me, they've been gradually increasing the Power Vs. Size ratio for a while

So how do they do this? Just upping the maximum allowed temperature? I'm sure they haven't invented some kind of nano-tech surface cooling enamel yet ;-)
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Re: movs catching fire

Postby Sleepwalker3 » Sun Dec 23, 2012 10:31 am

Mainly improvements in materials and processing I believe, they do state something to that effect. It's mostly for things like metal film resistors, not so much Carbon types. Whereas the 'mini' resistors used to be 1/16th or 1/8w, the are commonly now 1/4W and what used to be 1/4w size is mostly 0.5W now, some we get are 0.6 and I've even seen 0.7W is the same size.
The tend to be able to tolerate higher temperatures, presumably more flexible with better terminations and other improvements.
Take this one for example, they now rate it at 0.6W, but when I started in electronics, this would have been a 0.25W size. The 'Range Overview' says "This series of resistors is now rated at 0.6W (commercial spec) and 0.25W (CECC military spec).
Axial - 0.5 - 0.75W & Zero Ohm Links. High stability metal film resistors. Extremely low current-noise level with low temperature coefficient and close tolerance."
http://australia.rs-online.com/web/p/through-hole-fixed-resistors/0148506/?origin=PSF_433011|fp It's been very common over the past decade or two to see ratings for sizes like that doubled or even more, but it's more about the quality of the part.
Likewise Electrolytic Caps have shrunk dramatically over the years for a given size and capacity.
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Re: movs catching fire

Postby Sleepwalker3 » Sun Dec 23, 2012 10:40 am

Here's another example - This body size used to always be either 1/16W or 1/8W, but now is commonly 1/4W (.25W) or 1/2W (0.5W), this one being classed as 0.5W. The data sheet goes into the tests done and references some of the IEC test requirements for determining all this crap.
http://australia.rs-online.com/web/p/through-hole-fixed-resistors/1650151/
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Re: movs catching fire

Postby arakis » Mon Dec 24, 2012 4:17 am

Seems to me like using no surge protection is a safer option, expecialy in countries where the voltage swings are often...Just remember to backup often...
best regards FIlip.
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Re: movs catching fire

Postby Sleepwalker3 » Mon Dec 24, 2012 10:47 am

Odd, my post from before doesn't seem to be here.
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Re: movs catching fire

Postby hardcore » Mon Dec 24, 2012 5:50 pm

That "product" would NEVER be allowed under BSI approval

1. Plastics are not flame retardant
2. The linking of the sockets with wire is WRONG.
If you used the end socket ONLY and then pulled the full current through the cable, those internal wires would BURN.
3. Not allowed to "solder" wires like that, incase a socket overheats and the wires disconnect.
4. Clearance, where the "N" wire passes close to the bare "L" connections
5. Fake/poor quality resistors.
6. single strand wire used internally

This looks like some cheap mass produced Chinese shit made for the China market and re-branded.
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Re: movs catching fire

Postby arhi » Mon Dec 24, 2012 9:00 pm

well it was allowed into EU for a while :( .. now is banned from EU ( http://ec.europa.eu/consumers/dyna/rape ... m?rx_id=97 )
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Re: movs catching fire

Postby katjap » Mon Dec 24, 2012 11:46 pm

yeah.. nice thick ground wire in that... :-/
Now i have to open all our surge strips to check.
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Re: movs catching fire

Postby matseng » Tue Dec 25, 2012 12:27 am

hardcore wrote:That "product" would NEVER be allowed under BSI approval
2. The linking of the sockets with wire is WRONG.
If you used the end socket ONLY and then pulled the full current through the cable, those internal wires would BURN.
6. single strand wire used internally

Hmmm... Why would linkage of the sockets with a wire (instead of a busbar) be a problem? If the wire is of the same area as the cable leading into the powerstrip the cable would probably burn first due to less cooling and two wires being in close proximity.

And why would a single strand wire be bad internally? Within the unit there are no flexing, just as there are no flexing in the wall sockets outlets. Single stranded wire is very common as the fixed installation wiring in building walls.
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Re: movs catching fire

Postby erdabyz » Wed Dec 26, 2012 5:07 pm

matseng wrote:
hardcore wrote:That "product" would NEVER be allowed under BSI approval
2. The linking of the sockets with wire is WRONG.
If you used the end socket ONLY and then pulled the full current through the cable, those internal wires would BURN.
6. single strand wire used internally

Hmmm... Why would linkage of the sockets with a wire (instead of a busbar) be a problem? If the wire is of the same area as the cable leading into the powerstrip the cable would probably burn first due to less cooling and two wires being in close proximity.

And why would a single strand wire be bad internally? Within the unit there are no flexing, just as there are no flexing in the wall sockets outlets. Single stranded wire is very common as the fixed installation wiring in building walls.


As far as I remember single stranded wire is forbidden for home instalations in Spain. I don't know the exact reason but it's been forbidden for quite a while. I'll ask my father (an electrician) to check why. Maybe there's something wrong with it...
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Re: movs catching fire

Postby arhi » Wed Dec 26, 2012 8:40 pm

what is "single stranded wire" ?

I know about "solid wire" (one copper wire inside insulation) and this one is usually used for house installation (wires in wall's are solid, usually 3x3.5mm2 or 3x4mm2) and I know about "stranded wire" where there's a bundle of copper wires inside insulation and these are used for everything else (all your "soft" cables are with stranded wire, like your computer power cable).

what is "single" stranded wire?
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Re: movs catching fire

Postby Sleepwalker3 » Thu Dec 27, 2012 2:41 am

That's just another term for "solid core wire" but solid wire/solid core/single strand/single core/1 core, all means the same thing.
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Re: movs catching fire

Postby matseng » Thu Dec 27, 2012 2:52 am

erdabyz wrote:As far as I remember single stranded wire is forbidden for home instalations in Spain. I don't know the exact reason but it's been forbidden for quite a while. I'll ask my father (an electrician) to check why. Maybe there's something wrong with it...


Yes, please do - it would be interesting to know. As you say it seems that modern installations where the cables are pulled in tubes are done with single wire multi strand. But a bit older installations where the cables are nailed to (or inside the drywalls) are with multiple wires single strand.
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Re: movs catching fire

Postby bearmos » Thu Dec 27, 2012 3:23 am

interesting, solid core copper wire is still the standard for electrical installations in the USA AFAIK. I'd be curious as to why you'd want stranded wire in walls ( more flexibility for a cable that never moves and less current carrying capacity).

For the surge protector in question, most times you'll see stranded wire used in this application, since it's easier to get a good crimp and the wire is flexible, but I believe with all the right contacts, wire gauge, etc you can also crimp connectors onto solid core wire.
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