Gert
Thanks for that investigation that I have not had the time for recently!
Now, maybe, the standards writing committees will begin to take this issue
on board and do something about it as the problem is generally technically
trivial to solve - the major issue then being to ensure that the bleeder
device is always across the capacitor, and is not isolated from it by a
switch or contactor that the operator can put in the "open" position before
disconnecting the supply.
(The latter point can particularly apply to some filtered IEC, or similar,
power inlets with integral switches where the bleeder could be on the
opposite side of the contacts to the capacitor).
John Allen
Technical Consultant
Electromagnetics, Safety and Reliability Group
ERA Technology Ltd
Cleeve Rd
Leatherhead
Surrey KT22 7SA
Tel: +44 (0) 1372-367025 (Direct)
+44 (0) 1372-367000 (Switchboard)
Fax: +44 (0) 1372-367102 (Fax)
-----Original Message-----
From: Gert Gremmen [mailto:[email protected]]
Sent: 19 September 2002 11:57
To: John Allen
Cc: [email protected]
Subject: RE: Question: Discharge capacitance 0.1 uF
Hi John,
Even theory has to comply with practice, so i took my soldering iron...
I have to admit that modern capacitors do keep their charge too
long. I did some test with newer Y and X caps of 0.1 uF and they keep their
charge way too long - over 1 minute - without notable loss of
voltage (< 10%) (real life voltages choosen :310V)
Probably the quality of the dielectricum has been improved, or
the use of paper has been abandoned in favor of modern equivalent
plastics. (any one knows ?).
Of course the increased leakage of the older caps was not meant to be
part of the specs, and this is again a good example of how relying on hidden
specifications may in time lead to undesired results: standards ignoring the
effect of increased leakage resistance.
I also tried the discharge between two fingers, and found the result to
be unpleasant at least.
Time to change standards.......
Gert Gremmen
ce-test, qualified testing
-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of John Allen
Sent: Thursday, September 19, 2002 9:24 AM
To: 'Grasso, Charles'; 'Warren Birmingham'
Cc: [email protected]
Subject: RE: Question: Discharge capacitance 0.1 uF
Hi Charles, Warren
Seems that a few of us know what DOES happen and the longterm results, but
quite a few others don't believe that it does - and that even it does then
it is not very "important".
The difference between reality and theory!
I suggest that the "non-believers" try it for themselves - by unplugging a
suitable piece of equipment and picking it up - AND then touching the pins
of the plug!
(the unplugging process may need to be repeated a few times until the
capacitor is disconnected when the mains is high at the time of
disconnection and so gets a "decent" charge!)
However before they do try it, I suggest they wear safety boots and also use
a piece of equipment which can then be discarded due to the damage it
received when it fell on the foot and/or the ground!
Regards
John Allen
-----Original Message-----
From: Grasso, Charles [mailto:[email protected]]
Sent: 18 September 2002 19:07
To: 'John Allen'; [email protected]
Subject: RE: Question: Discharge capacitance 0.1 uF
Hi All,
>From personal experience I can tell you that the involuntary reaction to a
shock can have serious consequences to
the sales of a company. In a former life - a previous employer OEM'd a PC
from a Korean Company. The PC had all
the relevant marks but somehow the resistor that was supposed to bleed off
the caps didn't make it into
production. A customer , moving said model from one location to another,
touched the mains terminals and felt a shock.
The customer fell over, the PC landed on the customer, the customer sued and
the story ended up in the papers.
The sales of PCs essentially died after that. - All for the sake of one
resistor.
Best Regards
Charles Grasso
Senior Compliance Engineer
Echostar Communications Corp.
Tel: 303-706-5467
Fax: 303-799-6222
Cell: 303-204-2974
Email: [email protected]; <mailto:[email protected];
%20>
Email Alternate: [email protected] <mailto:[email protected]>
-----Original Message-----
From: John Allen [mailto:[email protected]]
Sent: Wednesday, September 18, 2002 11:11 AM
To: [email protected]
Subject: Question: Discharge capacitance 0.1 uF
Hello Folks
Tomonori Sato commented "However, I think discharge from 0.1uF capacitor
charged to the mains peak voltage can be quite uncomfortable."
I believe that to be true from personal experience and from having to
investigate the results of a number of such incidents, and so would remind
member of a point that I made several years ago on this forum:
The primary shock almost certainly will NOT hurt a person, but the
involuntary reaction TO the shock may well have much more
seriousconsequences.
This type of shock is often encountered by people who pick up equipment
which they have just unplugged from the AC mains in order to carry it
elsewhere. If they then touch the pins of the plug there are numerous
reported incidences of them involuntarily dropping the unit - and that can
possibly be on their own feet - and from a height of about 3ft/1m! If the
unit is more than a couple of pounds (about one kilo) then the injury to t!
he feet can be substantial.
Worse situations could occur in industrial equipment when a service engineer
opens a cabinet to perform a service operation - the reaction from the
"shock" could cause him to strike touch other hazardous electrical or
mechanical parts (which probably should also not be there, I do agree!)
which then cause him serious actual injury.
These types of incident do not make the equipment supplier very "popular" to
say the least, and could result in product liability claims.
The main basis for the claims would be that the supplier had not adequately
assessed the hazards and taken the appropriate simple precautions which are
easily and cheaply available - fit a bleeder resistor across the capacitor,
or use a filter with a resistor already built in (or with
transformer/inductor windings directly across the capacitor - which achieve
the same result) !
Again from personal experience I can say that it is a very "embarassing" and
un! comfortable experience to have to write to an injured or anno! yed
person, or to his employer, to say "sorry, but that is what the safety
standard allows". It is just not good "business sense".
Therefore, regardless of the requirements of the various standards and this
argument over capacitor value and/or charging voltage, I firmly believe that
the use of bleeder resistors should be considered effectively mandatory, and
have always recommended it to engineers I have advised on product safety.
Regards
John Allen
Technical Consultant
Electromagnetics, Safety and Reliability Group
ERA Technology Ltd
Cleeve Rd
Leatherhead
Surrey KT22 7SA
Tel: +44 (0) 1372-367025 (Direct)
+44 (0) 1372-367000 (Switchboard)
Fax: +44 (0) 1372-367102 (Fax)
----------------------------------------------------------------------
Replies to this message may be posted in the following public forum:
Question: <http://ieeepstc.mindcruiser.com/direct/topic/a/ID509830>
Discharge capacitance 0.1 uF
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<BODY lang=EN-US vLink=blue link=blue>
<DIV><SPAN class=192210311-19092002><FONT face=Arial color=#0000ff
size=2>Gert</FONT></SPAN></DIV>
<DIV><SPAN class=192210311-19092002><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=192210311-19092002><FONT face=Arial><FONT color=#0000ff><FONT
size=2>Thanks for that investigation that I have not had the time for<SPAN
class=487370811-19092002> recently</SPAN><SPAN
class=487370811-19092002>!</SPAN></FONT></FONT></FONT></SPAN></DIV>
<DIV><SPAN class=192210311-19092002><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><FONT face=Arial><FONT color=#0000ff><FONT size=2><SPAN
class=192210311-19092002>Now, maybe, the standards writing committees will
begin
to take this issue on board and do something about it <SPAN
class=487370811-19092002>as</SPAN> the problem is generally technically trivial
to solve - the major issue then being<SPAN
class=487370811-19092002> to e</SPAN></SPAN><SPAN
class=192210311-19092002>nsur<SPAN class=487370811-19092002>e</SPAN> that the
bleeder device is always across the capacitor, and is not isolated from it by a
switch or contactor that the operator can put in the "open" position before
disconnecting the supply<SPAN
class=487370811-19092002>.</SPAN></SPAN></FONT></FONT></FONT></DIV>
<DIV><FONT face=Arial><FONT color=#0000ff><FONT size=2><SPAN
class=192210311-19092002><SPAN
class=487370811-19092002></SPAN></SPAN></FONT></FONT></FONT> </DIV>
<DIV><SPAN class=192210311-19092002><FONT face=Arial><FONT color=#0000ff><FONT
size=2><SPAN class=487370811-19092002>(The latter point can particularly apply
to some filtered IEC, or similar, power inlets with integral switches where the
bleeder could be on the opposite side of the contacts to the
capacitor).</SPAN></FONT></FONT></FONT></SPAN></DIV><SPAN
class=192210311-19092002><FONT face=Arial color=#0000ff size=2><SPAN
class=487370811-19092002>
<P align=left>John Allen<BR>Technical Consultant<BR>Electromagnetics, Safety
and
Reliability Group<BR>ERA Technology Ltd<BR>Cleeve Rd<BR>Leatherhead<BR>Surrey
KT22 7SA<BR>Tel: +44 (0) 1372-367025 (Direct)<BR>+44 (0) 1372-367000
(Switchboard)<BR>Fax: +44 (0) 1372-367102 (Fax)</P></SPAN></FONT></SPAN>
<BLOCKQUOTE>
<DIV class=OutlookMessageHeader dir=ltr align=left><FONT face=Tahoma><FONT
size=2>-----Original Message-----<BR><B>From:</B> Gert Gremmen
[mailto:[email protected]]<BR><B>Sent:</B> 19 September 2002
11:57<BR><B>To:</B> John Allen<BR><B>Cc:</B>
[email protected]<BR><B>Subject:</B> RE: Question: Discharge
capacitance 0.1 uF<BR><BR></FONT></DIV></FONT>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=468265709-19092002>Hi
John,</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=468265709-19092002></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=468265709-19092002>Even theory has to comply with practice, so i
took my soldering iron...</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=468265709-19092002></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=468265709-19092002>I
have to admit that modern capacitors do keep their charge
too</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=468265709-19092002>long. I did some test with newer Y and X caps of 0.1
uF and they keep their</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=468265709-19092002>charge way too long - over 1 minute - without
notable
loss of</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=468265709-19092002>voltage (< 10%) (real life voltages choosen
:310V)</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=468265709-19092002>Probably the quality of the dielectricum has been
improved, or</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=468265709-19092002>the
use of paper has been abandoned in favor of modern
equivalent</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=468265709-19092002>plastics. (any one knows ?).</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=468265709-19092002>Of
course the increased leakage of the older caps was not meant to
be</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=468265709-19092002>part
of the specs, and this is again a good example of how relying
on hidden </SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=468265709-19092002>specifications may in time lead to undesired
results:
standards ignoring the</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=468265709-19092002>effect of increased leakage
resistance.</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=468265709-19092002></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=468265709-19092002>I
also tried the discharge between two fingers, and found the result
to</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=468265709-19092002>be
unpleasant at least.</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=468265709-19092002>Time
to change standards.......</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=468265709-19092002></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=468265709-19092002>Gert
Gremmen</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=468265709-19092002></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=468265709-19092002>ce-test, qualified testing</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=468265709-19092002></SPAN></FONT> </DIV>
<BLOCKQUOTE>
<DIV class=OutlookMessageHeader dir=ltr align=left><FONT face=Tahoma
size=2>-----Original Message-----<BR><B>From:</B>
[email protected]
[mailto:[email protected]]<B>On Behalf Of </B>John
Allen<BR><B>Sent:</B> Thursday, September 19, 2002 9:24 AM<BR><B>To:</B>
'Grasso, Charles'; 'Warren Birmingham'<BR><B>Cc:</B>
[email protected]<BR><B>Subject:</B> RE: Question: Discharge
capacitance 0.1 uF<BR><BR></FONT></DIV>
<DIV>
<DIV><SPAN class=289051207-19092002><FONT face=Arial><FONT
color=#0000ff><FONT size=2>Hi Charles<SPAN class=979411307-19092002>,
Warren</SPAN></FONT></FONT></FONT></SPAN></DIV>
<DIV><SPAN class=289051207-19092002><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=289051207-19092002><FONT face=Arial><FONT
color=#0000ff><FONT size=2>Seems <SPAN class=979411307-19092002>that
</SPAN>a few of us know what <SPAN class=979411307-19092002>DOES
</SPAN>happen<SPAN class=979411307-19092002> and the longterm
results,</SPAN> <SPAN class=979411307-19092002>but </SPAN>quite a few
others don't believe that it <SPAN class=979411307-19092002>does
-</SPAN><SPAN class=979411307-19092002> and that even it does then it is
not
very "important".</SPAN></FONT></FONT></FONT></SPAN></DIV>
<DIV><SPAN class=289051207-19092002><FONT face=Arial><FONT
color=#0000ff><FONT size=2><SPAN
class=979411307-19092002></SPAN></FONT></FONT></FONT></SPAN> </DIV>
<DIV><SPAN class=289051207-19092002><FONT face=Arial color=#0000ff
size=2><SPAN class=979411307-19092002>The difference between reality and
theory!</SPAN></FONT></SPAN></DIV>
<DIV><SPAN class=289051207-19092002><FONT face=Arial color=#0000ff
size=2><SPAN class=979411307-19092002></SPAN></FONT></SPAN> </DIV>
<DIV><SPAN class=289051207-19092002><FONT face=Arial color=#0000ff
size=2><SPAN class=979411307-19092002>I suggest that the "non-believers"
try
it for themselves - by unplugging a suitable piece of equipment and
picking it up - AND then touching the pins of the
plug!</SPAN></FONT></SPAN></DIV>
<DIV><SPAN class=289051207-19092002><FONT face=Arial color=#0000ff
size=2><SPAN class=979411307-19092002>(the unplugging process may need to
be
repeated a few times until the capacitor is disconnected when the mains is
high at the time of disconnection and so gets a "decent"
charge!)</SPAN></FONT></SPAN></DIV>
<DIV><SPAN class=289051207-19092002><FONT face=Arial color=#0000ff
size=2><SPAN class=979411307-19092002></SPAN></FONT></SPAN> </DIV>
<DIV><SPAN class=289051207-19092002><FONT face=Arial color=#0000ff
size=2><SPAN class=979411307-19092002>However before they do try it, I
suggest they wear safety boots and also use a piece of equipment which
can then be discarded due to the damage it received when it fell on the
foot
and/or the ground!</SPAN></FONT></SPAN></DIV>
<DIV><SPAN class=289051207-19092002><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=289051207-19092002><FONT face=Arial color=#0000ff
size=2>Regards</FONT></SPAN></DIV>
<DIV><SPAN class=289051207-19092002><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=289051207-19092002><FONT face=Arial color=#0000ff
size=2>John Allen</FONT></SPAN></DIV></DIV>
<BLOCKQUOTE>
<DIV class=OutlookMessageHeader dir=ltr align=left><FONT face=Tahoma
size=2>-----Original Message-----<BR><B>From:</B> Grasso, Charles
[mailto:[email protected]]<BR><B>Sent:</B> 18 September 2002
19:07<BR><B>To:</B> 'John Allen';
[email protected]<BR><B>Subject:</B> RE: Question: Discharge
capacitance 0.1 uF<BR><BR></FONT></DIV>
<DIV class=Section1>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">Hi
All,</SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY:
Arial"></SPAN></FONT> </P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">From personal
experience I can tell you that the involuntary reaction to a shock can
have serious consequences to<BR>the sales of a company. In a former life
-
a previous employer OEM'd a PC from a Korean Company. The PC had
all<BR>the relevant marks but somehow the resistor that was supposed to
bleed off the caps didn't make it into <BR>production. A customer ,
moving
said model from one location to another, touched the mains
terminals
and felt a shock.<BR>The customer fell over, the PC landed on the
customer, the customer sued and the story ended up in the papers.<BR>The
sales of PCs essentially died after that. - All for the sake of one
resistor.</SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY:
Arial"></SPAN></FONT> </P>
<DIV>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">Best
Regards<BR>Charles Grasso<BR>Senior Compliance Engineer<BR>Echostar
Communications Corp.<BR>Tel: 303-706-5467<BR>Fax:
303-799-6222<BR>Cell: 303-204-2974<BR>Email: <A
href="mailto:[email protected]; %20";>[email protected];
</A><BR>Email Alternate: <A
href="mailto:[email protected]";>[email protected]</A></SPAN></FONT></P>
<P class=MsoNormal><FONT face="Times New Roman" color=navy size=3><SPAN
style="FONT-SIZE: 12pt; COLOR: navy"></SPAN></FONT> </P></DIV>
<P class=MsoNormal style="MARGIN-LEFT: 0.5in"><FONT face=Tahoma
size=2><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: Tahoma">-----Original
Message-----<BR><B><SPAN style="FONT-WEIGHT: bold">From:</SPAN></B> John
Allen [mailto:[email protected]] <BR><B><SPAN
style="FONT-WEIGHT: bold">Sent:</SPAN></B> Wednesday, September 18, 2002
11:11 AM<BR><B><SPAN style="FONT-WEIGHT: bold">To:</SPAN></B>
</SPAN></FONT><FONT face=Tahoma size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY:
Tahoma">[email protected]</SPAN></FONT><FONT
face=Tahoma size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Tahoma"><BR><B><SPAN
style="FONT-WEIGHT: bold">Subject:</SPAN></B> Question: Discharge
capacitance 0.1 uF</SPAN></FONT></P>
<P class=MsoNormal style="MARGIN-LEFT: 0.5in"><FONT face="Times New
Roman"
size=3><SPAN style="FONT-SIZE: 12pt"></SPAN></FONT> </P>
<P class=MsoNormal
style="MARGIN-BOTTOM: 12pt; MARGIN-LEFT: 0.5in; MARGIN-RIGHT: 0in"><FONT
face="Times New Roman" size=3><SPAN style="FONT-SIZE: 12pt">Hello
Folks<BR><BR>Tomonori Sato commented "However, I think
discharge from 0.1uF capacitor charged to the mains peak voltage can be
quite uncomfortable."<BR><BR>I believe that to be true from personal
experience and from having to investigate the results of a number of such
incidents, and so would remind member of a point that I made several
years
ago on this forum: <BR><BR>The primary shock almost certainly will NOT
hurt a person, but the involuntary reaction TO the shock may well have
much more seriousconsequences. <BR><BR>This type of shock is often
encountered by people who pick up equipment which they have just
unplugged
from the AC mains in order to carry it elsewhere. If they then
touch the pins of the plug there are numerous reported incidences of them
involuntarily dropping the unit - and that can possibly be on their own
feet - and from a height of about 3ft/1m! If the unit is more than a
couple of pounds (about one kilo) then the injury to t! he feet can be
substantial. <BR><BR>Worse situations could occur in industrial equipment
when a service engineer opens a cabinet to perform a service operation -
the reaction from the "shock" could cause him to strike touch other
hazardous electrical or mechanical parts (which probably should also not
be there, I do agree!) which then cause him serious actual
injury.<BR><BR>These types of incident do not make the equipment supplier
very "popular" to say the least, and could result in product liability
claims.<BR><BR>The main basis for the claims would be that the supplier
had not adequately assessed the hazards and taken the appropriate simple
precautions which are easily and cheaply available - fit a bleeder
resistor across the capacitor, or use a filter with a resistor already
built in (or with transformer/inductor windings directly across the
capacitor - which achieve the same result) !<BR><BR>Again from personal
experience I can say that it is a very "embarassing" and un! comfortable
experience to have to write to an injured or anno! yed person, or to his
employer, to say "sorry, but that is what the safety standard allows". It
is just not good "business sense".<BR><BR>Therefore, regardless of the
requirements of the various standards and this argument over capacitor
value and/or charging voltage, I firmly believe that the use of bleeder
resistors should be considered effectively mandatory, and have always
recommended it to engineers I have advised on product
safety.<BR><BR>Regards<BR><BR>John Allen<BR>Technical
Consultant<BR>Electromagnetics, Safety and Reliability Group<BR>ERA
Technology Ltd<BR>Cleeve Rd<BR>Leatherhead<BR>Surrey KT22
7SA<BR>Tel: +44 (0) 1372-367025 (Direct)<BR>+44 (0)
1372-367000
(Switchboard)<BR>Fax: +44 (0) 1372-367102
(Fax)</SPAN></FONT></P>
<P style="MARGIN-LEFT: 0.5in"><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE:
12pt">----------------------------------------------------------------------<BR>Replies
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