Pete,
Glad to see your thoughts agree with mine. With large amplitude
voltage pulses there must be some EMC considerations that come into play
for equipment EMC compliance.
I really wish that some alternative abbreviation had been created
instead of ES. Many engineers would be looking for a Joule parameter for
an energy source, yet Joules don't get a direct mention in the IEC
62368-1 body text description (Why no entry in definitions?). Expressing
ES as a voltage, current and charged capacitance (no inductive current)
makes it multi-option classification. Further when it comes to
telecommunications TNV circuits, those are classified by DC working
voltage alone.
Thus they are ES1 or ES2 DC working voltage circuits not simply ES1 or
ES2 circuits as that would drag all the other ES factors in.
Regards,
Mick
Safety and Telecom
Standards
mjmay...@gmail.com
https://ict-surge-protection-essays.co.uk/
------ Original Message ------
From: "Pete Perkins" <peperkin...@cs.com>
To: "Mick Maytum" <mjmay...@gmail.com>; EMC-PSTC@listserv.ieee.org
Sent: 13/03/2019 06:11:38
Subject: RE: [PSES] classification of the output
Mick, Thanx for the reply given on this thread.
I am familiar with the 60479 clauses you describe. My
overall comment is that 60479 folks primary focus is on preventing VF
(not killing people). Much of what you quoted relates to such electric
shock situations. Because of the data spread there probably are a few
folks who lie below the curves shown in the standard. Tasers meet
these requirements yet there are occasional deaths with their use; the
‘almost perfect weapon’ in my opinion.
In the product standards the allowed electric shock
level is always set much lower so that the VF region is not involved.
The upper limit to electric shock from equipment is the
Letgo-immobilization limit of 5mArms/7mApk under fault conditions. The
long time separation to allow the heart to reset doesn’t come into play
for this effect so it is irrelevant. The peak current is the major
factor that needs to be controlled.
:>) br, Pete
Peter E Perkins, PE
Principal Product Safety & Regulatory Affairs Consultant
PO Box 23427
Tigard, ORe 97281-3427
503/452-1201
IEEE Life Fellow
p.perk...@ieee.org
Entropy ain’t what it used to be
From: Mick Maytum <mjmay...@gmail.com>
Sent: Tuesday, March 12, 2019 1:03 PM
To:EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] classification of the output
Joe Randolph and I talked about “pulsed power” delivery at the 2019
ATIS-PEG conference last week and how it should be treated.
A good starting point is the IEC 60479 series of documents on “Effects
of current on human beings and livestock”. IEC 62368-1 mentions the
time locked IEC TS 60479-1:2005, but the current version is IEC
60479-1:2018. The IEC TS 60479-2:2017 variant is particularly
interesting as clause 9 covers “Effects of current pulse bursts and
random complex irregular waveforms”. For sequential pulses separated by
> 300 ms there isn’t a cumulative effect on the heart and each pulse
can be treated as single, non-repetitive pulse of current. For safety,
I believe pulsed power systems will insert this separation time when
any non-load currents are detected to delay any following power pulse.
Thus only the effects of a single power pulse need to be evaluated
provided the safety separation is >0.3 s. Primarily IEC TS 60479-2:2017
is seeking to establish a “no fibrillation” condition, which is higher
stress level than you’d want for a safety standard.
A 2018 ATIS-PEG conference paper on IEC TS 60479-2:2017 gave an example
evaluation using the quoted pulsed currents produced by a TASER® gun.
Safety tip - if anyone is pointing a TASER® gun at you, yell out you
have a pre-existing medical condition.
Image removed by sender.
Regards,
Mick
Safety and Telecom
Standards
mjmay...@gmail.com
https://ict-surge-protection-essays.co.uk/
------ Original Message ------
From: "Joe Randolph" <j...@randolph-telecom.com>
To: EMC-PSTC@listserv.ieee.org
Sent: 12/03/2019 17:54:36
Subject: Re: [PSES] classification of the output
Hi Pete:
This discussion reminds me of some things I have been hearing about
“digital power” as a way to deliver large amounts of power while
keeping the circuit classification to ES1 or ES2. A company called
Voltserver has been promoting (and deploying) this technology.
I know few details about the scheme, and I’m not familiar with how IEC
62368-1 evaluates things such as touch current.
However, as I understand it, the “digital power” method uses a series
of short pulses with off periods during which the power sourcing
device attempts to detect a fault condition. The power is immediately
cut off if a fault condition is detected. I have heard that the pulse
frequency is in the range of 7 KHz, and the voltages can be up to 380
V. The key to making this scheme even plausible is that the system
must respond VERY quickly to a fault condition (such as a human
touching a live conductor).
I’m interested in hearing your thoughts (and hopefully Rich Nute’s
thoughts too) regarding how the touch current tests in IEC 62368-1
might apply to such a system. I don’t know whether such a system
would pass or fail the IEC 62368-1 tests.
Regardless of whether such a system would pass or fail the existing
tests in IEC-62368-1, I think the important thing is to go back to
first principles and evaluate whether the proposed “digital power” can
be made sufficiently safe to prevent harm to humans.
Thanks,
Joe Randolph
Telecom Design Consultant
Randolph Telecom, Inc.
781-721-2848 (USA)
j...@randolph-telecom.com
http://www.randolph-telecom.com
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