UPSs and surge protection.

[kony]

okay, i have a picture of the failed supply posted here:
http://home.silencescape.net/~slack/

i plugged it back in just now, and the smoke was coming from an area
just to the right of the bottom of the fan, as you look at it in the
picture i posted. somewhere between a capacitor which is almost
entirely obscured by dirty black and white cables and a what i take to
be a small yellow transformer marked MITAC [numbers] I-MAC 9946. being
a bit of a pussy and not having safety glasses i didn't get too close
to it whilst it was smoking but i guess i can further risk my eyesight
if that's not specific enough.

That supply has an elaborate surge filter, consisting of the 2 coils at
the top of the picture and the blue rectangular capacitor between them,
plus the 2 blue disk capacitors at the lower left, on the AC
receptacle. But it may not work well without a grounded electrical
system.

No, that will definitely not filter surges of any
significant magnitude. Mostly, it is meant to filter out
common AC noise on a stable line. Most of it (excluding a
few, maybe 2-4 of the round blue ceramic caps) is
hot-neutral or in series with either, does not need grounded
system. The grounded portion definitely doesn't filter
surges.

However, that PSU looks passingly like some Compaq used in
past years on their low-end systems. They spec'd it for
around 150W, maybe 200, and (not sure but "probably") it
isn't likely to have much 5VSB current potential. While the
generator is the most likely suspect, it's also possible the
supply simply isn't adequate for a more modern system's
potential to run more PS/2 and/or USB from 5VSB power, maybe
even a combination of these two factors.

Some switching power supplies are prone to breaking down with high
input voltage, and it seems the +5V standby part breaks down most,
probably because it's left on all the time. I'd replace the burnt
parts, the power transistor (next to the smaller transformer), and the
green electrolytic capacitor, using a low ESR type with a slightly
higher voltage rating than the existing one, and see what happens.

Frankly, a $15 (USD) 250W Sparkle PSU makes it of limited
value to repair that particular unit. IF it were
proprietary or an expensive higher capacity power supply it
might be a better idea, but as is it may be worn to the
point that it's useful life for any semi-modern system is
past the point of good return on time spent.

 

[Guest]

On 7 Jul 2005 00:55:36 -0700, (e-mail address removed)
wrote:

No, that will definitely not filter surges of any
significant magnitude. Mostly, it is meant to filter out
common AC noise on a stable line. Most of it (excluding a
few, maybe 2-4 of the round blue ceramic caps) is
hot-neutral or in series with either, does not need grounded
system. The grounded portion definitely doesn't filter
surges.

While they are meant for noise filtering, I found they blocked surges
well, namely from my small refrigerator and fluorescent desk lamp. My
computer would lock or restart when I used a power supply without any
such filter, but by adding the missing components to the PC board, the
system became completely stable.

Frankly, a $15 (USD) 250W Sparkle PSU makes it of limited
value to repair that particular unit

I keep forgetting how low prices have dropped, even for quality.

 

[kony]

While they are meant for noise filtering, I found they blocked surges
well, namely from my small refrigerator and fluorescent desk lamp. My
computer would lock or restart when I used a power supply without any
such filter, but by adding the missing components to the PC board, the
system became completely stable.

Different situation, the magnitude of your problem was
slight, and short. In such a situation the minor inductance
plus the filter caps are a bit of a reservoir, but in a case
with a generator that is continually producing problems, the
result may be as was seen- although the PSU had that circuit
(which isn't all that elaborate, rather typical for any
name-brand PSU) it still wasn't enough.

An active PFC circuit may provide even further benefit in
such a scenario, but still it's not meant to deal with these
fluctuations.

I keep forgetting how low prices have dropped, even for quality.

Being excess stock from a prior era helps result in low
cost, but they aren't quite top-shelf either, the typical
Sparkles for $15 have cheap Yate Loon fans that are prone to
early failure. It was just a passing suggestion though, a
power supply with a bit more reserve may also be a little
more apt to survive brief surges, but still not a situation
with a generator. The whole 'site (or at minimum all
potentially-effected devices) should have a line conditioner
or different generator (perhaps a 2nd one, isolating some if
not all of the higher current devices or whichever division
is viable).

 

[Goldenpi]

To really get rid of those problems, You need a on-line UPS (Read:
expencive). They run from battery all the time, and thus feeds a
constant and extremly clean voltage.

I tried to build one - the battery and invertor were easy and cheap to get.
But just try finding an affordable power supply that can convert mains in to
12V DC out at 200W continuous. And thats without worrying about proper
charging of the batteries, just feeding power in them until the output
voltage matches that of the power supply. If you want a good invertor (Mine
is a 230V, 50Hz, sine-ish output) thats more money.

 

[kony]

I tried to build one - the battery and invertor were easy and cheap to get.

A suitable battery and invertor are typically more expensive
than a simple AC-DC supply you mention below.

But just try finding an affordable power supply that can convert mains in to
12V DC out at 200W continuous.

What's hard about that? Just grab any decent PC power
supply, something rated for at least 17A on 12V rail, then
put a load on the 5V rail too, to stabilize the output.
Otherwise, it's also easy to find 12V switching supplies
online. They're usually more expensive than a PC supply but
there are also some deals to be had on them at ebay or
various surplus/salvage companies.

And thats without worrying about proper
charging of the batteries, just feeding power in them until the output
voltage matches that of the power supply.

Even a $0.50 LM317 configured as a current limiter will do
the job (see LM317 datasheet, there may even be a simple
schematic for battery charging), but if you want more
elaborate control then you'll have to define those
parameters. Some battery manufacturers also provide spec
sheets for various models' optimal charge voltage- more
information never hurts.

If you want a good invertor (Mine
is a 230V, 50Hz, sine-ish output) thats more money.

Sure, good equipment costs more - no surprise there.
However, there are ready-made products so if you don't have
the parts or experience then why make it hard on yourself?

You don't actually "need" such an UPS though, a line
conditioner w/filtering (internal or add-on module) will be
sufficient and you can put a standard (suitable capacity)
UPS after it in the supply chain.

 

[mikael.hautin]

Excuse me, but I think youre hiding the MOV term to prove something.

Because you do think us mortals should not know what is an MOV, you did
say the term 'MOV' 13 times in your last post. Is that better than not
reading numbers, or whatever ? I think not.

But, you provided a link on Metal Oxide Varistors that shows us a table
which is full of number that I, poor mortal, do not understand.

I was said, "for 10 minutes of reliance, you'll have to manifold : 1,8
x P, where P is the power consumed by the hardware connected to the
UPS. I make the math :
600 x 1.8 = 1080 AU.

Knowing I do not need 10 minutes of reliance, I buy an APM 800VA UPS.

From now, I do not have any surge problems anymore, and I do not fear

power cuts.

As said before, "personal attack" describes perfectly the situation.

Lets hypothesize :

You are working on your computer. Obviously, you do use linux. While
you are compiling your freshly-downloaded kernel, you're editing
configuration files and installing som RPMs of the new SSH daemon.
Suddenly, *blackout* !

You do wait the power gets back, and start your computer. But surprise
! The configuration files you were editing are now corrupt ! So is the
ssh demon, without speaking of the kernel.

Lets imagine the worse. Once, when I was under Windows(a long time
ago), i was gaming(isnt windows for this ?). Blackout. I start my
computer, and get the following message : NTLDR file missing. Insert
boot disk ....
The windows bootloader file was corrupted and I had to reinstall
windows. Moreover, one of my hard drives, tired of those bad cares,
choosed to die at ths moment.

These two stories happened to me. Those are not numbers, those are not
grids, those are proofs. Proof of whatever you do, you probably need an
UPS. You can care about the duration it can handle if you have to use
your computer during 30 minutes after the power has been cut. I have
one, surge protected, and I am very happy of it.