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];
Email Alternate: [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: Discharge capacitance 0.1 uF
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<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
to this message may be posted in the following public forum:<BR><A
href="http://ieeepstc.mindcruiser.com/direct/topic/a/ID509830";>Question:
Discharge capacitance 0.1 uF</A>
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