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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<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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