[PSES] electric shock from capacitor discharge

[Richard Nute]

I am interested in knowing what constructions, situations, and products
where a capacitive discharge into a body could take place.

I am aware of the X and Y capacitors discharge at the prongs of a power
plug.  I don't immediately know of other situations or products that might
discharge a capacitor into a body.  

I would appreciate descriptions of such discharges into a body, not
conjecture.  Preferably, normal conditions and some single-fault conditions.


Do we need to include capacitive discharge requirements in the safety
standards?

Stay safe!
Rich



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Re: [PSES] electric shock from capacitor discharge

[lauren . crane]

Hi Rich,

Discharge requirements are already in some electrical safety standards. Not at 
my desk so recall is poor, but likely 61010 or even NFPA 79 have something 
about caps with stored energy above x joules have to discharge within N seconds 
of power off...

Cheers,
-Lauren

Sent from my mobile phone - please excuse typos, brevity, etc.

On Sep 29, 2020, at 4:27 PM, Richard Nute  wrote:



I am interested in knowing what constructions, situations, and products where a 
capacitive discharge into a body could take place.

I am aware of the X and Y capacitors discharge at the prongs of a power plug.  
I don’t immediately know of other situations or products that might discharge a 
capacitor into a body.

I would appreciate descriptions of such discharges into a body, not conjecture. 
 Preferably, normal conditions and some single-fault conditions.

Do we need to include capacitive discharge requirements in the safety standards?

Stay safe!

Rich

-


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discussion list. To post a message to the list, send your e-mail to 
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Re: [PSES] electric shock from capacitor discharge

[Richard Nute]

 

 

Hi Lauren:

 

Thanks, but I recognize that many standards include such requirements.  I am 
looking for instances (other than the pins of a power plug) where such 
requirements must be invoked. 

 

Stay safe!

Rich

 

From: lauren.cr...@us.tel.com  
Sent: Tuesday, September 29, 2020 2:52 PM
To: ri...@ieee.org
Cc: EMC-PSTC@listserv.ieee.org
Subject: Re: [PSES] electric shock from capacitor discharge

 

Hi Rich, 

 

Discharge requirements are already in some electrical safety standards. Not at 
my desk so recall is poor, but likely 61010 or even NFPA 79 have something 
about caps with stored energy above x joules have to discharge within N seconds 
of power off...

 

Cheers,

-Lauren

Sent from my mobile phone - please excuse typos, brevity, etc.





On Sep 29, 2020, at 4:27 PM, Richard Nute mailto:ri...@ieee.org> > wrote:

 

I am interested in knowing what constructions, situations, and products where a 
capacitive discharge into a body could take place.

I am aware of the X and Y capacitors discharge at the prongs of a power plug.  
I don’t immediately know of other situations or products that might discharge a 
capacitor into a body.  

I would appreciate descriptions of such discharges into a body, not conjecture. 
 Preferably, normal conditions and some single-fault conditions.  

Do we need to include capacitive discharge requirements in the safety standards?

Stay safe!

Rich






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Re: [PSES] electric shock from capacitor discharge

[BANSI PATEL]

Rich:

 

There are incidents where there are capacitors in the equipment, that can have 
hazardous energy.

UL 1778, safety standard for UPS has requirement for protection of safety 
personnel, where there is clause to make sure that makes sure that energy in 
the capacitor is discharged before service personnel has an access to the 
capacitor. 

 

Please be safe

 

Stay Home - Stop the Spread – Save Lives

 

Best Regards

 

Bansi Patel

M: 909-260-9403

bansipate...@gmail.com <mailto:bansipate...@gmail.com> 

 

From: Richard Nute  
Sent: Tuesday, September 29, 2020 3:04 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] electric shock from capacitor discharge

 

 

 

Hi Lauren:

 

Thanks, but I recognize that many standards include such requirements.  I am 
looking for instances (other than the pins of a power plug) where such 
requirements must be invoked. 

 

Stay safe!

Rich

 

 

From: lauren.cr...@us.tel.com <mailto:lauren.cr...@us.tel.com>  
mailto:lauren.cr...@us.tel.com> > 
Sent: Tuesday, September 29, 2020 2:52 PM
To: ri...@ieee.org <mailto:ri...@ieee.org> 
Cc: EMC-PSTC@listserv.ieee.org <mailto:EMC-PSTC@listserv.ieee.org> 
Subject: Re: [PSES] electric shock from capacitor discharge

 

Hi Rich, 

 

Discharge requirements are already in some electrical safety standards. Not at 
my desk so recall is poor, but likely 61010 or even NFPA 79 have something 
about caps with stored energy above x joules have to discharge within N seconds 
of power off...

 

Cheers,

-Lauren

Sent from my mobile phone - please excuse typos, brevity, etc.

 

On Sep 29, 2020, at 4:27 PM, Richard Nute mailto:ri...@ieee.org> > wrote:

 

I am interested in knowing what constructions, situations, and products where a 
capacitive discharge into a body could take place.

I am aware of the X and Y capacitors discharge at the prongs of a power plug.  
I don’t immediately know of other situations or products that might discharge a 
capacitor into a body.  

I would appreciate descriptions of such discharges into a body, not conjecture. 
 Preferably, normal conditions and some single-fault conditions.  

Do we need to include capacitive discharge requirements in the safety standards?

Stay safe!

Rich

 

-


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David Heald mailto:dhe...@gmail.com> > 


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Re: [PSES] electric shock from capacitor discharge

[MIKE SHERMAN]

Rich --

Are you including old CRTs as capacitors? I recall that, even with the early 
Macs, you had to be careful to discharge the tube if you were going to mess 
around inside.

Mike

> On 09/29/2020 4:27 PM Richard Nute  wrote:
> 
> 
> 
> 
> I am interested in knowing what constructions, situations, and products 
> where a capacitive discharge into a body could take place.
> 
> I am aware of the X and Y capacitors discharge at the prongs of a power 
> plug.  I don’t immediately know of other situations or products that might 
> discharge a capacitor into a body. 
> 
> I would appreciate descriptions of such discharges into a body, not 
> conjecture.  Preferably, normal conditions and some single-fault conditions. 
> 
> Do we need to include capacitive discharge requirements in the safety 
> standards?
> 
> Stay safe!
> 
> Rich
> 
> 
> -
> 
> 
> This message is from the IEEE Product Safety Engineering Society emc-pstc 
> discussion list. To post a message to the list, send your e-mail to 
> mailto:emc-p...@ieee.org >
> 
> All emc-pstc postings are archived and searchable on the web at: 
> http://www.ieee-pses.org/emc-pstc.html
> 
> Attachments are not permitted but the IEEE PSES Online Communities site 
> at http://product-compliance.oc.ieee.org/ can be used for graphics (in 
> well-used formats), large files, etc.
> 
> Website: http://www.ieee-pses.org/
> Instructions: http://www.ieee-pses.org/list.html (including how to 
> unsubscribe) http://www.ieee-pses.org/list.html
> List rules: http://www.ieee-pses.org/listrules.html
> 
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> David Heald mailto:dhe...@gmail.com >
> 

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Re: [PSES] electric shock from capacitor discharge

[Dan Roman]

I can attest to the CRT tubes.  I worked in a TV shop in high school and was 
asked to get all of the old 25” color CRTs out of the basement because the 
refurb place was picking them up.  They had been stored down there for a long 
time but I picked one up with the anode pressed against my stomach and I got 
quite a jolt through my shirt.  They act like caps and can store a charge a lot 
longer than I thought they would!

 

Stay safe, stay well.

 

Dan

 

From: MIKE SHERMAN [mailto:msherma...@comcast.net] 
Sent: Tuesday, September 29, 2020 8:58 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] electric shock from capacitor discharge

 

Rich -- 

 

Are you including old CRTs as capacitors? I recall that, even with the early 
Macs, you had to be careful to discharge the tube if you were going to mess 
around inside. 

 

Mike 

On 09/29/2020 4:27 PM Richard Nute mailto:ri...@ieee.org> > 
wrote: 

 

 

 

I am interested in knowing what constructions, situations, and products where a 
capacitive discharge into a body could take place.

I am aware of the X and Y capacitors discharge at the prongs of a power plug.  
I don’t immediately know of other situations or products that might discharge a 
capacitor into a body.  

I would appreciate descriptions of such discharges into a body, not conjecture. 
 Preferably, normal conditions and some single-fault conditions. 

Do we need to include capacitive discharge requirements in the safety standards?

Stay safe!

Rich


- 
 

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Re: [PSES] electric shock from capacitor discharge

[lauren . crane]

Hi Rich,

This may fall into ‘anecdotal’ but I recall CRT televisions could store charge. 
I can’t recall if this was in an intentional capacitor, or capacitance inherent 
in the tube, etc.

As a very practical, first hand experience matter, I used to work on small ion 
implanters (essentially linear accelerators) that had a terminal elevated to 
several hundred thousand volts DC relative to ground. The votage –elevated 
section stored charge from the operation (i.e., accidental capacitor), and we 
had to be careful to discharge it before servicing. The cables that ran from an 
AC isolation transformer to the elevated voltage terminal were particularly 
tricky as they had to be covered with a semiconducting insulation. Those cables 
had to be touched along the whole length with a grounding stick to discharge.

I would say any device that has voltages above about 3000 kVDC could store 
charge.

Best Regards,
-Lauren

From: Richard Nute 
Sent: Tuesday, September 29, 2020 5:04 PM
To: TEH EHS Crane, Lauren 
Cc: emc-pstc@LISTSERV.IEEE.ORG
Subject: RE: [PSES] electric shock from capacitor discharge



Hi Lauren:

Thanks, but I recognize that many standards include such requirements.  I am 
looking for instances (other than the pins of a power plug) where such 
requirements must be invoked.

Stay safe!
Rich


From: lauren.cr...@us.tel.com<mailto:lauren.cr...@us.tel.com> 
mailto:lauren.cr...@us.tel.com>>
Sent: Tuesday, September 29, 2020 2:52 PM
To: ri...@ieee.org<mailto:ri...@ieee.org>
Cc: EMC-PSTC@listserv.ieee.org<mailto:EMC-PSTC@listserv.ieee.org>
Subject: Re: [PSES] electric shock from capacitor discharge

Hi Rich,

Discharge requirements are already in some electrical safety standards. Not at 
my desk so recall is poor, but likely 61010 or even NFPA 79 have something 
about caps with stored energy above x joules have to discharge within N seconds 
of power off...

Cheers,
-Lauren
Sent from my mobile phone - please excuse typos, brevity, etc.

On Sep 29, 2020, at 4:27 PM, Richard Nute 
mailto:ri...@ieee.org>> wrote:


I am interested in knowing what constructions, situations, and products where a 
capacitive discharge into a body could take place.

I am aware of the X and Y capacitors discharge at the prongs of a power plug.  
I don’t immediately know of other situations or products that might discharge a 
capacitor into a body.

I would appreciate descriptions of such discharges into a body, not conjecture. 
 Preferably, normal conditions and some single-fault conditions.

Do we need to include capacitive discharge requirements in the safety standards?

Stay safe!

Rich


-

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discussion list. To post a message to the list, send your e-mail to 


All emc-pstc postings are archived and searchable on the web at:
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formats), large files, etc.

Website:  http://www.ieee-pses.org/
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Mike Cantwell 

For policy questions, send mail to:
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Re: [PSES] electric shock from capacitor discharge

[Richard Nute]

 

 

Here is a summary of capacitor discharge situations:

 

Operator conditions:  Vacuum tube radio/tv with isolated metal trim.  (John 
Woodgate)

Service conditions:  Vacuum tube radar servo controller.  (Doug Powell)

Service conditions:  UPS capacitor discharge before servicing.  (Bansi Patel)

Operator conditions:  Defibrillator automatic discharge. (Dave Osborn)

Operator conditions:  CRT capacitance.  (Mike Sherman) (Dan Roman)

Service conditions:  Power factor correction for motor drives  (Ted Eckert) 
(Julia Curson) (Mike Sherman)

Service conditions:  Small ion implanters.  (Lauren Crane)

 

We still need to identify in our safety standards when a charged capacitance 
requires a safeguard.

 

Thanks for your responses.

 

Stay safe!

Rich

 

 


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[PSES] AW: [PSES] electric shock from capacitor discharge

[Dürrer Bernd]

Hello Richard,

Please have a look at the requirements of IEC 61800-5-1, clause 4.3.11: 
“Capacitors within a PDS shall be discharged to a voltage less than 60 V, or to 
a residual charge less than 50 μC, within 5 s after the removal of power from 
the PDS. […] In the case of plugs or similar devices that can be disconnected 
without the use of a tool, the withdrawal of which results in the exposure of 
conductors (e.g. pins), the discharge time shall not exceed 1 s.” I presume 
that the longer time span of 5 s is meant for the case of equipment that is 
connected to the fixed installation and where discharge is only possible after 
opening the enclosure (e.g. for maintenance and installation). Typically, 
opening the enclosure will take a few seconds after power removal while the 
pins of the power plug are directly accessible.

Kind regards,

Bernd

Von: Richard Nute 
Gesendet: Mittwoch, 30. September 2020 00:04
An: EMC-PSTC@LISTSERV.IEEE.ORG
Betreff: Re: [PSES] electric shock from capacitor discharge



Hi Lauren:

Thanks, but I recognize that many standards include such requirements.  I am 
looking for instances (other than the pins of a power plug) where such 
requirements must be invoked.

Stay safe!
Rich


From: lauren.cr...@us.tel.com<mailto:lauren.cr...@us.tel.com> 
mailto:lauren.cr...@us.tel.com>>
Sent: Tuesday, September 29, 2020 2:52 PM
To: ri...@ieee.org<mailto:ri...@ieee.org>
Cc: EMC-PSTC@listserv.ieee.org<mailto:EMC-PSTC@listserv.ieee.org>
Subject: Re: [PSES] electric shock from capacitor discharge

Hi Rich,

Discharge requirements are already in some electrical safety standards. Not at 
my desk so recall is poor, but likely 61010 or even NFPA 79 have something 
about caps with stored energy above x joules have to discharge within N seconds 
of power off...

Cheers,
-Lauren
Sent from my mobile phone - please excuse typos, brevity, etc.

On Sep 29, 2020, at 4:27 PM, Richard Nute 
mailto:ri...@ieee.org>> wrote:


I am interested in knowing what constructions, situations, and products where a 
capacitive discharge into a body could take place.

I am aware of the X and Y capacitors discharge at the prongs of a power plug.  
I don’t immediately know of other situations or products that might discharge a 
capacitor into a body.

I would appreciate descriptions of such discharges into a body, not conjecture. 
 Preferably, normal conditions and some single-fault conditions.

Do we need to include capacitive discharge requirements in the safety standards?

Stay safe!

Rich

-


This message is from the IEEE Product Safety Engineering Society emc-pstc 
discussion list. To post a message to the list, send your e-mail to 
mailto:emc-p...@ieee.org>>

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[PSES] electric shock from capacitor discharge -- late adds

[Richard Nute]

 

Here is a summary of capacitor discharge situations with late adds:

 

Operator conditions:  Vacuum tube radio/tv with isolated metal trim.  (John 
Woodgate)

Service conditions:  Vacuum tube radar servo controller.  (Doug Powell)

Service conditions:  UPS capacitor discharge (automatic or time delay) before 
servicing.  (Bansi Patel)

Operator conditions:  Defibrillator automatic discharge. (Dave Osborn)

Operator conditions:  CRT capacitance.  (Mike Sherman) (Dan Roman)

Service conditions:  Power factor correction capacitor for motor drives  (Ted 
Eckert) (Julia Curson) (Mike Sherman)

Service conditions:  Small ion implanters.  (Lauren Crane)

Service conditions:  Microwave oven capacitors with integrated bleeders.  (Adam 
Dixon)

Service conditions:  Electrostatic speaker amplifiers.  (Adam Dixon)

Service conditions:  Electric welding systems.  (Adam Dixon)

Service conditions:  Industrial laser systems.  (Inadvertently omitted from 
first list).)  (Pete Perkins)

 

Adam (in Atlanta) Dixon sent a URL of a capacitor discharge event that is 
worthwhile reading.  Note the picture of the capacitor!

 

https://ehs.berkeley.edu/lessons-learned/lesson-learned-injury-caused-high-voltage-capacitor-discharge

 

 

We still need to identify in our safety standards when a charged capacitance 
requires a safeguard.  For operator conditions, we need automatic discharge as 
is done for defibrillators.  For service conditions, we need either an 
automatic discharge safeguard or an instructional safeguard.  (We can ignore 
vacuum tube devices and crt devices as it is doubtful any new products will use 
such devices!)

 

Thanks for your responses.

 

Stay safe!

Rich

 

 

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Re: [PSES] [EXTERNAL] Re: [PSES] electric shock from capacitor discharge

[Ted Eckert]

Hi Rich,

I can’t think of many cases of modern IT equipment with a significant risk of 
capacitance discharge through the plug. However, I could foresee motor-driven 
equipment where it could be an issue. The manufacturer might put a power factor 
correction capacitor across the line to compensate for the inductive load of 
the motor. The motor should bleed off the charge of the capacitor, but there 
may still be some residual charge when the user pulls the plug. You probably 
wouldn’t have that large of a capacitor on a plug-connected motor appliance, 
but it is possible.

It’s been more than a decade since I worked with large motor-drive appliances, 
so my memory of their workings isn’t great. I’m sure there is somebody on this 
list server who can correct any error I’ve made in my statements.

Ted Eckert
The opinions expressed are my own and do not necessarily reflect those of my 
employer.


From: MIKE SHERMAN 
Sent: Tuesday, September 29, 2020 5:58 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [EXTERNAL] Re: [PSES] electric shock from capacitor discharge

Rich --

Are you including old CRTs as capacitors? I recall that, even with the early 
Macs, you had to be careful to discharge the tube if you were going to mess 
around inside.

Mike
On 09/29/2020 4:27 PM Richard Nute mailto:ri...@ieee.org>> 
wrote:




I am interested in knowing what constructions, situations, and products where a 
capacitive discharge into a body could take place.

I am aware of the X and Y capacitors discharge at the prongs of a power plug.  
I don’t immediately know of other situations or products that might discharge a 
capacitor into a body.

I would appreciate descriptions of such discharges into a body, not conjecture. 
 Preferably, normal conditions and some single-fault conditions.

Do we need to include capacitive discharge requirements in the safety standards?

Stay safe!

Rich

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Re: [PSES] [EXTERNAL] Re: [PSES] electric shock from capacitor discharge

[Julia Curson]

I second Ted’s comment on motor drives. The capacitor charge risk post switch 
off is usually handled with a time delayed interlock on the housing cabinet, 
along with an acrylic sheet shield or such covering to protect against 
accidental contact if the cabinet is open. And of course ubiquitous signage as 
required by the standards.

On 30 Sep 2020, at 04:22, Ted Eckert 
<07cf6ebeab9d-dmarc-requ...@listserv.ieee.org> wrote:


Hi Rich,

I can’t think of many cases of modern IT equipment with a significant risk of 
capacitance discharge through the plug. However, I could foresee motor-driven 
equipment where it could be an issue. The manufacturer might put a power factor 
correction capacitor across the line to compensate for the inductive load of 
the motor. The motor should bleed off the charge of the capacitor, but there 
may still be some residual charge when the user pulls the plug. You probably 
wouldn’t have that large of a capacitor on a plug-connected motor appliance, 
but it is possible.

It’s been more than a decade since I worked with large motor-drive appliances, 
so my memory of their workings isn’t great. I’m sure there is somebody on this 
list server who can correct any error I’ve made in my statements.

Ted Eckert
The opinions expressed are my own and do not necessarily reflect those of my 
employer.


From: MIKE SHERMAN 
Sent: Tuesday, September 29, 2020 5:58 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [EXTERNAL] Re: [PSES] electric shock from capacitor discharge

Rich --

Are you including old CRTs as capacitors? I recall that, even with the early 
Macs, you had to be careful to discharge the tube if you were going to mess 
around inside.

Mike
On 09/29/2020 4:27 PM Richard Nute mailto:ri...@ieee.org>> 
wrote:




I am interested in knowing what constructions, situations, and products where a 
capacitive discharge into a body could take place.

I am aware of the X and Y capacitors discharge at the prongs of a power plug.  
I don’t immediately know of other situations or products that might discharge a 
capacitor into a body.

I would appreciate descriptions of such discharges into a body, not conjecture. 
 Preferably, normal conditions and some single-fault conditions.

Do we need to include capacitive discharge requirements in the safety standards?

Stay safe!

Rich

-


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mailto:emc-p...@ieee.org>>

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Th

Re: [PSES] [EXTERNAL] Re: [PSES] electric shock from capacitor discharge

[MIKE SHERMAN]

I've seen some motor caps on industrial induction motors whose capacitance gave 
me pause. I think we specified a minimum bleed down time to allow before 
servicing.
Mike Sherman
Graco Inc.

> On 09/29/2020 10:21 PM Ted Eckert 
> <07cf6ebeab9d-dmarc-requ...@listserv.ieee.org> wrote:
> 
> 
> 
> Hi Rich,
> 
> 
> I can’t think of many cases of modern IT equipment with a significant 
> risk of capacitance discharge through the plug. However, I could foresee 
> motor-driven equipment where it could be an issue. The manufacturer might put 
> a power factor correction capacitor across the line to compensate for the 
> inductive load of the motor. The motor should bleed off the charge of the 
> capacitor, but there may still be some residual charge when the user pulls 
> the plug. You probably wouldn’t have that large of a capacitor on a 
> plug-connected motor appliance, but it is possible.
> 
> 
> It’s been more than a decade since I worked with large motor-drive 
> appliances, so my memory of their workings isn’t great. I’m sure there is 
> somebody on this list server who can correct any error I’ve made in my 
> statements.
> 
> 
> Ted Eckert
> 
> The opinions expressed are my own and do not necessarily reflect those of 
> my employer.
> 
>  
> 
> 
> From: MIKE SHERMAN 
>     Sent: Tuesday, September 29, 2020 5:58 PM
> To: EMC-PSTC@LISTSERV.IEEE.ORG
> Subject: [EXTERNAL] Re: [PSES] electric shock from capacitor discharge
> 
> 
> Rich --
> 
>  
> 
> Are you including old CRTs as capacitors? I recall that, even with the 
> early Macs, you had to be careful to discharge the tube if you were going to 
> mess around inside.
> 
>  
> 
> Mike
> 
> > > 
> > On 09/29/2020 4:27 PM Richard Nute  > mailto:ri...@ieee.org > wrote:
> > 
> > 
> > 
> > 
> > I am interested in knowing what constructions, situations, and 
> > products where a capacitive discharge into a body could take place.
> > 
> > I am aware of the X and Y capacitors discharge at the prongs of a 
> > power plug.  I don’t immediately know of other situations or products that 
> > might discharge a capacitor into a body. 
> > 
> > I would appreciate descriptions of such discharges into a body, not 
> > conjecture.  Preferably, normal conditions and some single-fault 
> > conditions. 
> > 
> > Do we need to include capacitive discharge requirements in the 
> > safety standards?
> > 
> > Stay safe!
> > 
> > Rich
> > 
> > 
> > -
> > 
> > 
> > This message is from the IEEE Product Safety Engineering Society 
> > emc-pstc discussion list. To post a message to the list, send your e-mail 
> > to mailto:emc-p...@ieee.org >
> > 
> > All emc-pstc postings are archived and searchable on the web at: 
> > http://www.ieee-pses.org/emc-pstc.html 
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> > 
> > Attachments are not permitted but the IEEE PSES Online Communities 
> > site at http://product-compliance.oc.ieee.org/ 
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> >  can be used for graphics (in well-used formats), large files, etc.
> > 
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Re: [PSES] [EXTERNAL] Re: [PSES] electric shock from capacitor discharge

[Pete Perkins]

Rich et al,It’s been a while but, as I remember, servicing laser 
products used on industrial equipment required consideration of the stored cap 
charge that could be accessible to the technician.  

 

:>) br,  Pete

 

Peter E Perkins, PE

Principal Product Safety & Regulatory Affairs Consultant

PO Box 1067

Albany, ORe  97321-0413

 

503/452-1201

 

IEEE Life Fellow

IEEE PSES 2020 Distinguished Lecturer

 <mailto:p.perk...@ieee.org> p.perk...@ieee.org

 

Entropy ain’t what it used to be

 

From: MIKE SHERMAN  
Sent: Wednesday, September 30, 2020 8:42 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] [EXTERNAL] Re: [PSES] electric shock from capacitor 
discharge

 

I've seen some motor caps on industrial induction motors whose capacitance gave 
me pause. I think we specified a minimum bleed down time to allow before 
servicing. 

Mike Sherman 

Graco Inc. 

On 09/29/2020 10:21 PM Ted Eckert 
<07cf6ebeab9d-dmarc-requ...@listserv.ieee.org 
<mailto:07cf6ebeab9d-dmarc-requ...@listserv.ieee.org> > wrote: 

 

 

Hi Rich,

 

I can’t think of many cases of modern IT equipment with a significant risk of 
capacitance discharge through the plug. However, I could foresee motor-driven 
equipment where it could be an issue. The manufacturer might put a power factor 
correction capacitor across the line to compensate for the inductive load of 
the motor. The motor should bleed off the charge of the capacitor, but there 
may still be some residual charge when the user pulls the plug. You probably 
wouldn’t have that large of a capacitor on a plug-connected motor appliance, 
but it is possible.

 

It’s been more than a decade since I worked with large motor-drive appliances, 
so my memory of their workings isn’t great. I’m sure there is somebody on this 
list server who can correct any error I’ve made in my statements.

 

Ted Eckert

The opinions expressed are my own and do not necessarily reflect those of my 
employer.

 

 

From: MIKE SHERMAN mailto:msherma...@comcast.net> > 
Sent: Tuesday, September 29, 2020 5:58 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG <mailto:EMC-PSTC@LISTSERV.IEEE.ORG> 
Subject: [EXTERNAL] Re: [PSES] electric shock from capacitor discharge

 

Rich -- 

 

Are you including old CRTs as capacitors? I recall that, even with the early 
Macs, you had to be careful to discharge the tube if you were going to mess 
around inside. 

 

Mike 

On 09/29/2020 4:27 PM Richard Nute mailto:ri...@ieee.org> > 
wrote:

 

 

 

I am interested in knowing what constructions, situations, and products where a 
capacitive discharge into a body could take place.

I am aware of the X and Y capacitors discharge at the prongs of a power plug.  
I don’t immediately know of other situations or products that might discharge a 
capacitor into a body.  

I would appreciate descriptions of such discharges into a body, not conjecture. 
 Preferably, normal conditions and some single-fault conditions. 

Do we need to include capacitive discharge requirements in the safety standards?

Stay safe!

Rich


- 


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discussion list. To post a message to the list, send your e-mail to 
mailto:emc-p...@ieee.org> >

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Re: [PSES] [EXTERNAL] Re: [PSES] electric shock from capacitor discharge

[John Allen]

I believe most Standards that have a requirement regarding it, require bleed 
off within 60 seconds.

From: Pete Perkins <0061f3f32d0c-dmarc-requ...@listserv.ieee.org>
Sent: Wednesday, September 30, 2020 10:48 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] [EXTERNAL] Re: [PSES] electric shock from capacitor 
discharge

Rich et al,It’s been a while but, as I remember, servicing laser 
products used on industrial equipment required consideration of the stored cap 
charge that could be accessible to the technician.

:>) br,  Pete

Peter E Perkins, PE
Principal Product Safety & Regulatory Affairs Consultant
PO Box 1067
Albany, ORe  97321-0413

503/452-1201

IEEE Life Fellow
IEEE PSES 2020 Distinguished Lecturer
p.perk...@ieee.org<mailto:p.perk...@ieee.org>

Entropy ain’t what it used to be

From: MIKE SHERMAN mailto:msherma...@comcast.net>>
Sent: Wednesday, September 30, 2020 8:42 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG<mailto:EMC-PSTC@LISTSERV.IEEE.ORG>
Subject: Re: [PSES] [EXTERNAL] Re: [PSES] electric shock from capacitor 
discharge

I've seen some motor caps on industrial induction motors whose capacitance gave 
me pause. I think we specified a minimum bleed down time to allow before 
servicing.
Mike Sherman
Graco Inc.
On 09/29/2020 10:21 PM Ted Eckert 
<07cf6ebeab9d-dmarc-requ...@listserv.ieee.org<mailto:07cf6ebeab9d-dmarc-requ...@listserv.ieee.org>>
 wrote:


Hi Rich,

I can’t think of many cases of modern IT equipment with a significant risk of 
capacitance discharge through the plug. However, I could foresee motor-driven 
equipment where it could be an issue. The manufacturer might put a power factor 
correction capacitor across the line to compensate for the inductive load of 
the motor. The motor should bleed off the charge of the capacitor, but there 
may still be some residual charge when the user pulls the plug. You probably 
wouldn’t have that large of a capacitor on a plug-connected motor appliance, 
but it is possible.

It’s been more than a decade since I worked with large motor-drive appliances, 
so my memory of their workings isn’t great. I’m sure there is somebody on this 
list server who can correct any error I’ve made in my statements.

Ted Eckert
The opinions expressed are my own and do not necessarily reflect those of my 
employer.


From: MIKE SHERMAN mailto:msherma...@comcast.net>>
Sent: Tuesday, September 29, 2020 5:58 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG<mailto:EMC-PSTC@LISTSERV.IEEE.ORG>
Subject: [EXTERNAL] Re: [PSES] electric shock from capacitor discharge

Rich --

Are you including old CRTs as capacitors? I recall that, even with the early 
Macs, you had to be careful to discharge the tube if you were going to mess 
around inside.

Mike
On 09/29/2020 4:27 PM Richard Nute mailto:ri...@ieee.org>> 
wrote:




I am interested in knowing what constructions, situations, and products where a 
capacitive discharge into a body could take place.

I am aware of the X and Y capacitors discharge at the prongs of a power plug.  
I don’t immediately know of other situations or products that might discharge a 
capacitor into a body.

I would appreciate descriptions of such discharges into a body, not conjecture. 
 Preferably, normal conditions and some single-fault conditions.

Do we need to include capacitive discharge requirements in the safety standards?

Stay safe!

Rich

-


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