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Why is PC chasis put on voltage when earth/ground wire is missing ?!?

 
 
Skybuck Flying
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      05-14-2011, 10:29 PM
Hello,

Apperently PC's have "incoming netfilters/powerfilters" in the Netherlands
possibly Europe which filter out fluctuations caused by other equipment on
power lines.

One design which seems to be in use is a netfilter which tries to use the
earth/grounding wire to get rid of the excessive fluctuations... however if
the earth wire is not available it seems to dump the additional voltage to
the chasis, or it puts the chasis under/on voltage for some other reason ?!?

So my question is:

Does the netfilter indeed output excessive voltages onto the chasis ?

If so why does it do this ?

Can it not simply dump the excessive fluctuations to the other wire ?

Perhaps it does not know which wire to use because of the way plugs can be
plugged in ?
(+ - versus - +)

If so then that could explain why it can't dump additional voltage to the
2-wire system and instead choses to dump it to the chasis.

Can this voltage on the chasis slowly build up over time ? Does it become
like a battery or something ?

However if these are not the reasons to put the chasis under/on voltage then
what is the real reason to put the chasis on voltage in case there is no
earth wire ?!?

Bye,
Skybuck.


 
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Paul
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      05-15-2011, 01:51 AM
Skybuck Flying wrote:
> Hello,
>
> Apperently PC's have "incoming netfilters/powerfilters" in the Netherlands
> possibly Europe which filter out fluctuations caused by other equipment on
> power lines.
>
> One design which seems to be in use is a netfilter which tries to use the
> earth/grounding wire to get rid of the excessive fluctuations... however if
> the earth wire is not available it seems to dump the additional voltage to
> the chasis, or it puts the chasis under/on voltage for some other reason ?!?
>
> So my question is:
>
> Does the netfilter indeed output excessive voltages onto the chasis ?
>
> If so why does it do this ?
>
> Can it not simply dump the excessive fluctuations to the other wire ?
>
> Perhaps it does not know which wire to use because of the way plugs can be
> plugged in ?
> (+ - versus - +)
>
> If so then that could explain why it can't dump additional voltage to the
> 2-wire system and instead choses to dump it to the chasis.
>
> Can this voltage on the chasis slowly build up over time ? Does it become
> like a battery or something ?
>
> However if these are not the reasons to put the chasis under/on voltage then
> what is the real reason to put the chasis on voltage in case there is no
> earth wire ?!?
>
> Bye,
> Skybuck.
>
>


There are some example schematics here. The first one is a schematic of the ATX
supply. You can see the details of the input filter, and C2 and C3 would be
the things making leakage current.

http://www.pavouk.org/hw/en_atxps.html

Now, for this link, when you click, please be patient. It can take a couple minutes
for this server to respond. The "metal box" described in this PDF, is a professional
filter for equipment, used to perform the same function as the simpler circuit inside
the ATX supply. The wording in the description states the purpose -

http://web.archive.org/web/200311141...i/N+Series.PDF

"designed to provide superior common-mode and differential-mode attenuation"

For one of the two types of attenuation, a capacitor needs to be connected to
ground, to form a filter. The filter is designed to trap signals at "Megahertz".
But an accidental side effect, is the capacitor also shunts a small amount of
50Hz or 60Hz current, into the ground.

If the appropriate capacitors were disconnected, then you'd stop getting a shock,
but then, more switching noise from the ATX supply, would flow backwards into
your supply mains, disrupting your ability to view over-the-air television
signals.

The electrical code in your country, will state how to safely handle this
situation. An electrician can advise you on what to do next (you don't even
have to pay him for a visit - describe your problem over the phone to him).
I cannot offer any "home solutions", because if I told you what to do next,
you could hurt someone. Your electrician can solve the problem safely,
or at least give a cost estimate as to how expensive it would be to
fix.

HTH,
Paul
 
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tuinkabouter
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Posts: n/a
 
      05-15-2011, 10:55 AM
Op 5/15/2011 12:29 AM, Skybuck Flying schreef:
> Hello,
>
> Apperently PC's have "incoming netfilters/powerfilters" in the Netherlands
> possibly Europe which filter out fluctuations caused by other equipment on
> power lines.
>
> One design which seems to be in use is a netfilter which tries to use the
> earth/grounding wire to get rid of the excessive fluctuations... however if
> the earth wire is not available it seems to dump the additional voltage to
> the chasis, or it puts the chasis under/on voltage for some other reason ?!?
>
> So my question is:
>
> Does the netfilter indeed output excessive voltages onto the chasis ?
>
> If so why does it do this ?
>
> Can it not simply dump the excessive fluctuations to the other wire ?
>
> Perhaps it does not know which wire to use because of the way plugs can be
> plugged in ?
> (+ - versus - +)
>
> If so then that could explain why it can't dump additional voltage to the
> 2-wire system and instead choses to dump it to the chasis.
>
> Can this voltage on the chasis slowly build up over time ? Does it become
> like a battery or something ?
>
> However if these are not the reasons to put the chasis under/on voltage then
> what is the real reason to put the chasis on voltage in case there is no
> earth wire ?!?


hey moron,

This is already answered in another group you posted too.
Besides that YOU mentioned a website with the answers.

--
pim.
 
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Hal
Guest
Posts: n/a
 
      05-15-2011, 03:23 PM

"Skybuck Flying" <(E-Mail Removed)> wrote in message
news:d6d7d$4dcf0208$54192c06$(E-Mail Removed)1.n b.home.nl...
> Hello,
>
> Apperently PC's have "incoming netfilters/powerfilters" in the Netherlands
> possibly Europe which filter out fluctuations caused by other equipment on
> power lines.
>
> One design which seems to be in use is a netfilter which tries to use the
> earth/grounding wire to get rid of the excessive fluctuations... however
> if the earth wire is not available it seems to dump the additional voltage
> to the chasis, or it puts the chasis under/on voltage for some other
> reason ?!?
>
> So my question is:
>
> Does the netfilter indeed output excessive voltages onto the chasis ?
>
> If so why does it do this ?
>
> Can it not simply dump the excessive fluctuations to the other wire ?
>
> Perhaps it does not know which wire to use because of the way plugs can be
> plugged in ?
> (+ - versus - +)
>
> If so then that could explain why it can't dump additional voltage to the
> 2-wire system and instead choses to dump it to the chasis.
>
> Can this voltage on the chasis slowly build up over time ? Does it become
> like a battery or something ?
>
> However if these are not the reasons to put the chasis under/on voltage
> then what is the real reason to put the chasis on voltage in case there is
> no earth wire ?!?
>
> Bye,
> Skybuck.


Simply: regular netfilters contains two capacitors of the same value (the so
called Y-capacitors). The midpoint (fig. 1
http://www.ce-mag.com/archive/2001/j...rgerian36.html ) is connected
to the chassis. These capacitors carry about 0.25 -0.5 mA ~ current. Both
the ~ terminals in the PC are floting. As the mains outside the PC is
grounded, and in case the chassis of the PC is not connected to ground, the
chassis will, because of voltage dividing, end up at a potential of half the
mains voltage, capable of delivering 0.5 mA. So you can get a shock when
touching a not grounded PC. Especially care is needed if more than one
device with such a filter is connected to the same outlet. Currents add up
an can become hazardes.
So don't use your lips to sense the temperature somewere in the PC as I
sometimes did :-).

Hal


 
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Skybuck Flying
Guest
Posts: n/a
 
      05-15-2011, 04:39 PM

"tuinkabouter" <(E-Mail Removed)> wrote in message
news:iqobmt$9e1$(E-Mail Removed)...
> Op 5/15/2011 12:29 AM, Skybuck Flying schreef:
>> Hello,
>>
>> Apperently PC's have "incoming netfilters/powerfilters" in the
>> Netherlands
>> possibly Europe which filter out fluctuations caused by other equipment
>> on
>> power lines.
>>
>> One design which seems to be in use is a netfilter which tries to use the
>> earth/grounding wire to get rid of the excessive fluctuations... however
>> if
>> the earth wire is not available it seems to dump the additional voltage
>> to
>> the chasis, or it puts the chasis under/on voltage for some other reason
>> ?!?
>>
>> So my question is:
>>
>> Does the netfilter indeed output excessive voltages onto the chasis ?
>>
>> If so why does it do this ?
>>
>> Can it not simply dump the excessive fluctuations to the other wire ?
>>
>> Perhaps it does not know which wire to use because of the way plugs can
>> be
>> plugged in ?
>> (+ - versus - +)
>>
>> If so then that could explain why it can't dump additional voltage to the
>> 2-wire system and instead choses to dump it to the chasis.
>>
>> Can this voltage on the chasis slowly build up over time ? Does it become
>> like a battery or something ?
>>
>> However if these are not the reasons to put the chasis under/on voltage
>> then
>> what is the real reason to put the chasis on voltage in case there is no
>> earth wire ?!?

>
> hey moron,


Hey Moron,

> This is already answered in another group you posted too.
> Besides that YOU mentioned a website with the answers.


No LOL.

These websites explained why there was a voltage on the chasis from a
reverse enginering point of view.

My question is from a design point of view.

Why was it designed like this in the first place ?!

Bye,
Skybuck.


 
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Skybuck Flying
Guest
Posts: n/a
 
      05-15-2011, 04:52 PM

"Hal" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
>
> "Skybuck Flying" <(E-Mail Removed)> wrote in message
> news:d6d7d$4dcf0208$54192c06$(E-Mail Removed)1.n b.home.nl...
>> Hello,
>>
>> Apperently PC's have "incoming netfilters/powerfilters" in the
>> Netherlands possibly Europe which filter out fluctuations caused by other
>> equipment on power lines.
>>
>> One design which seems to be in use is a netfilter which tries to use the
>> earth/grounding wire to get rid of the excessive fluctuations... however
>> if the earth wire is not available it seems to dump the additional
>> voltage to the chasis, or it puts the chasis under/on voltage for some
>> other reason ?!?
>>
>> So my question is:
>>
>> Does the netfilter indeed output excessive voltages onto the chasis ?
>>
>> If so why does it do this ?
>>
>> Can it not simply dump the excessive fluctuations to the other wire ?
>>
>> Perhaps it does not know which wire to use because of the way plugs can
>> be plugged in ?
>> (+ - versus - +)
>>
>> If so then that could explain why it can't dump additional voltage to the
>> 2-wire system and instead choses to dump it to the chasis.
>>
>> Can this voltage on the chasis slowly build up over time ? Does it become
>> like a battery or something ?
>>
>> However if these are not the reasons to put the chasis under/on voltage
>> then what is the real reason to put the chasis on voltage in case there
>> is no earth wire ?!?
>>
>> Bye,
>> Skybuck.

>
> Simply: regular netfilters contains two capacitors of the same value (the
> so called Y-capacitors). The midpoint (fig. 1
> http://www.ce-mag.com/archive/2001/j...rgerian36.html ) is connected
> to the chassis. These capacitors carry about 0.25 -0.5 mA ~ current. Both
> the ~ terminals in the PC are floting. As the mains outside the PC is
> grounded, and in case the chassis of the PC is not connected to ground,
> the chassis will, because of voltage dividing, end up at a potential of
> half the mains voltage, capable of delivering 0.5 mA. So you can get a
> shock when touching a not grounded PC. Especially care is needed if more
> than one device with such a filter is connected to the same outlet.
> Currents add up an can become hazardes.
> So don't use your lips to sense the temperature somewere in the PC as I
> sometimes did :-).


This was already discussed, this is looking at it from an reverse enginering
point of view.

Now the question is:

Why was it designed this way ?!?

Cannot it now be designed in a different way so that the chasis does not
need to be under/on voltage ?!?

Bye,
Skybuck.


 
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Ben
Guest
Posts: n/a
 
      05-15-2011, 05:20 PM


> This was already discussed, this is looking at it from an reverse
> enginering point of view.


> Now the question is:


> Why was it designed this way ?!?


> Cannot it now be designed in a different way so that the chasis does not
> need to be under/on voltage ?!?


> Bye,
> Skybuck.



Read the ****ing manual.

This apparatus MUST BE EARTHED !

So, connecting to a Non Earthed AC source is totally on your own risk.



 
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Skybuck Flying
Guest
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      05-15-2011, 07:01 PM

"Ben" <(E-Mail Removed)> wrote in message
news:4dd00b7e$0$850$(E-Mail Removed)...
>
>
>> This was already discussed, this is looking at it from an reverse
>> enginering point of view.

>
>> Now the question is:

>
>> Why was it designed this way ?!?

>
>> Cannot it now be designed in a different way so that the chasis does not
>> need to be under/on voltage ?!?

>
>> Bye,
>> Skybuck.

>
>
> Read the ****ing manual.


It's not in the ****ing manual:

Seasonic S12 600 watt manual:

http://www.seasonicusa.com/images/Br...S12Manual1.pdf

> This apparatus MUST BE EARTHED !


Why does it need to be earthed ? Why does it need a third earth wire ?

Why cannot it not simply use two wires without earth and without putting the
chasis under voltage ?!?

Why does it need to put the chasis under voltage when it's not earthed ?

You have not answered any of my questions and seem to think that these
questions are documented somewhere which so far appears not to be the case.

Bye,
Skybuck.


 
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Skybuck Flying
Guest
Posts: n/a
 
      05-15-2011, 07:09 PM
Antec 1200 case does not mention it as well:

http://www.antec.com/pdf/manuals/1200_EN%20manual.pdf

I am starting to get a little ****ed off right about now.

There is no way I could have known that first of all earthing is required
and second of all what would happen if it's not earthed... -> chasis under
power.

Seems to me these companies might be sueable... only thing which is in doubt
if it was in the law by the time I bought and assembled and damage the PC...
(laws might have been updated in 2001 however might not apply to every home
build before that time).

Perhaps law says: "it's required to earth computers"... in that case the
companies might get away with it.
However law also says what to do when not earthed, though to difficult for
me to tell.

But perhaps not because I did not know what would happen if it was not
earthed and that if I would connect my devices that there would be a voltage
on the chasis:

Thus negleance of critical information and thus perhaps sueable for
withholding critical information which could lead to damage.

Bye,
Skybuck.


 
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Dave Platt
Guest
Posts: n/a
 
      05-15-2011, 10:03 PM
In article <bbac8$4dd001b9$54192c06$(E-Mail Removed)1.nb.hom e.nl>,
Skybuck Flying <(E-Mail Removed)> wrote:

>These websites explained why there was a voltage on the chasis from a
>reverse enginering point of view.
>
>My question is from a design point of view.
>
>Why was it designed like this in the first place ?!


The filters are intended to create a connection between each side of
the power line, and ground, which has a low impedance at high (RF)
frequencies. This connection is created with a capacitor, connected
between the power line conductor(s) and ground. By presenting a low
impedance at RF, the capacitor creates what one might call a
"preferred" path for the RF noise... it's "easier" for the noise to
flow to ground, than it is for it to flow back onto the power line (if
it was created inside the equipment) or into the equipment (if it was
coming in from the power line).

Noise can be present on either or both of the power-line conductors,
(and if it's on both, it can be in the same polarity or the opposite
polarity). This means that you need a capacitor from each conductor
to ground.

The capacitors do allow a small amount of power-line current to flow
through them... their impedance at 50 or 60 Hz is quite high, so only
a small amount of current leaks through.

If you disconnect the equipment chassis from ground, this leaves the
chassis connected to the two sides of the power line by capacitors of
equal value (usually). If you're using "non-balanced" power (with one
side being "neutral" and close to ground voltage), this capacitive
"voltage divider" will leave the chassis sitting at around half of the
power-line voltage. However, this will usually not present any sort
of safety/shock hazard if you touch the chassia and are grounded,
because the high impedance of the capacitors at 50 or 60 Hz limits the
current to well below the shock limit.

If you're in a country which uses symmetrical, "balanced" power, then
the chassis will remain at nearly ground voltage even if you
disconnect it from ground.

I believe it's *not* a good idea to run this sort of equipment (three
wires, with one wire connected to the chassis and to earth-ground) in a
non-grounded mode. Even if doing so doesn't create a safety hazard,
it defeats much of the benefit of the noise-filtering components, and
it may create hum/buzz problems (if e.g. you connect it to another
component, via a simple non-balanced audio or video cable with RCA
plugs/jacks, and the other component *is* properly grounded).

Here in the U.S., I believe it's considered to be unsafe to run such
components this way... "defeating the ground prong" on a 3-wire plug
is generally considered to be a hazardous or improper installation,
and might void the warranty. That's part of what I meant by "grossly
defective" in my earlier message.

Appliances which are designed with a 2-wire (non-grounded) power cord
and plug are built differently... they don't connect RF filtering
capacitors to the chassis, and they are usually "double-insulated" so
that a fault in the wire insulation can't bring it into contact with a
metal chassis that someone could touch.

--
Dave Platt <(E-Mail Removed)> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
 
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