Joe,
My memories of the early 13 A plugs in the UK is their
consistency rather than inconsistency. I was in TV design at
that time. Traditionally the early TV power supplies used a
half-wave rectifier, so the chassis was either L or N. When
the 13 A plug became widely used the chassis was
In message 6.1.0.6.2.20130618130138.056f9...@pop.randolph-telecom.com,
dated Tue, 18 Jun 2013, Joe Randolph j...@randolph-telecom.com writes:
Someone from the UK explained to me that in the UK, there was a time
when two different mains plug styles were widely used. When a customer
went to a
In message 009d01ce6c4c$71a42460$54ec6d20$@blueyonder.co.uk, dated
Tue, 18 Jun 2013, John Allen john_e_al...@blueyonder.co.uk writes:
BTW, a lot of the imported products actually arrive at the UK consumer
with a Continental 2.5A two-pin plug fitted and a Schuko to BS1363
adaptor to adapt that
!). Now that's
what I call leakage current! J
John
From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Mick Maytum
Sent: 18 June 2013 15:31
To: EMC-PSTC@listserv.ieee.org
Cc: Joe Randolph
Subject: Re: [PSES] safety 60950 and surge suppression circuits - 13A plugs
Joe,
My
Hi Joe,
I was asking the question like yours about 5 years ago here. Until now I'm not
sure how to understand this all.
My device was USB-RS485 interface powered from 12V DC (user should select
himself some AC/DC or use 12V battery backuped power source).
As RS485 can be up to 1200m and I
Hi Rich:
Thanks for insight on this. I think your remarks, copied below,
explain the logic behind clause 6.1.2, but still leave questions about
the thinking behind clause 6.2.
The hazard that is mitigated by the isolation
barrier is that of a fault in the equipment across the
isolation barrier
Hi Joe:
On 5/31/2013 8:16 PM, Joe Randolph
wrote:
Hi Rich:
Thanks for responding to my request for an explanation of the
logic
behind allowing SPDs across isolation barriers.
Overall, the
Hi Rich:
Thanks for responding to my request for an explanation of the logic
behind allowing SPDs across isolation barriers.
Overall, the principles you outline seem reasonable if the equipment has
a reliable earth connection. I'm not yet convinced that these
principles adequately address
Hi Joe:
Sorry for the delay in my reply to your questions.
SPDs are used on mains circuits, both between the
poles and poles to earth. In this latter application,
the SPD is in parallel with basic insulation.
SPDs are also used on low-voltage external circuits
that are subject to transient
Hi Bill:
On 5/21/2013 7:34 PM, Bill Owsley
wrote:
A surge into a 300 volt SPD transfers that surge voltage to the
open ground (chassis) and there is now a hazard !!!
An SPD will not operate
Rich,
Given your rational that surge protective components
(SPCs), such as MOVs or GDTs, can have a fault mode anywhere
between a short-circuit and an open-circuit, looks like
there is a disconnect in the test levels.
In the open-circuit situation, the SPC does not divert
current and
Hi Rich:
The apparent contradiction that I was trying to describe can be
summarized as follows:
a) The safety insulation barrier must withstand a hipot test of, say,
1500 VRMS
b) It is permissible to bridge this safety insulation barrier with a SPD
that breaks down at, say, 300 VRMS
In other
Rich -
Notwithstanding your statements about the safety insulation needing to
meet the testing, I have always viewed the testing with the SPC removed or
disabled to be an allowance, since in almost every instance, will cause a
false indication of breakdown of the safety insulation by means of
Throwing in my 2 cents:
Hipot test values are based on expected transients. The concern with the
transient overvoltages is that they could punch through insulation needed for
safety and subsequently hazardous voltages can be allowed to reach areas where
they should not. The function of an SPD
Hi Scott:
Your explanation makes sense but it presumes the SPD shunts the current
to ground.
It would appear to me that the SPD is allowed to simply bridge the
isolation barrier. That is the aspect that seems contradictory to
me.
In 60950-1 clauses 6.1.2 and 6.2 (the ones I work with most
So the Safety engineer said the single fault condition was an open ground...
Now what?
A surge into a 300 volt SPD transfers that surge voltage to the open ground
(chassis) and there is now a hazard !!!
Thus the position, I've been told while sticking my fingers in my ears, The
SPD's have to
Hi Rich:
I'm hoping that you can provide one of your straightforward Rich
Nute Explanations for the apparent contradiction behind the
rationale that allows a surge protection component to be placed across a
required safety isolation barrier, and then removed for the purpose of
performing the
Hi Joe:
Very quickly...
SPDs are not considered reliable components or assemblies.
The safety standards anticipate a failure -- anywhere from
open-circuit to short-circuit.
In the event of an open-circuit, there is no indication of
such a failure. And, of course, all transients then pass
Hi Bill:
SPDs, regardless of configuration, are notorious for being
prone to failure, either short-circuit or open-circuit or
any value of resistance between those two extremes. (One
cannot predict the energy the SPD will be required to
dissipate.)
From a safety point of view, all such
In message 518feba9.7000...@ieee.org, dated Sun, 12 May 2013, Richard
Nute ri...@ieee.org writes:
As for the requirement for the GDT to pass the hi-pot test...
??? I don't have any rationale for this.
If its seal was broken, letting the magic gas out, would it arc over at
a lower voltage?
On 5/12/2013 12:39 PM, John Woodgate wrote:
In message 518feba9.7000...@ieee.org, dated Sun, 12 May 2013,
Richard Nute ri...@ieee.org writes:
As for the requirement for the GDT to pass the hi-pot test...
??? I don't have any rationale for this.
If its seal was broken, letting the magic gas
Assuming no tracking from impurities, GDT failure mode is typically open.
And personal (anecdotal) experience bears this as correct.
But have seen test reports where simulated lightning strikes with enough
energy cause failure of body such that CTI adversely affected enough to stay
lo-Z.
Brian
John,
It is true that people used to worry about GDTs
venting. In venting the GDT sparkover voltage greatly
increased. In fact, there was a US trend to include a
Back-Up (air) Gap (BUG) across the GDT component in case
this happens. In fact, due to contamination, these BUGs were
more
Hi Bill,
You can use MOV (VDR) primary to PE as long as you have reliable earth.
Reliable earth is considered for pluggable equipment type B or permanently
connected equipment. For pluggable equipment type A, you would need additional
earthing point, what is usually not acceptable for clients.
Sent: Saturday, May 11, 2013 12:29 PM
Subject: Re: [PSES] safety 60950 and surge suppression circuits
Hi Bill,
You can use MOV (VDR) primary to PE as long as you have reliable earth.
Reliable earth is considered for pluggable equipment type B or permanently
I'm running into a dilemma. Not being a Safety Engineer myself, but rubbing
elbows with them...
On a piece of ITE equipment, I need some surge suppression for worldwide
markets with one annoying requirement for 4 kV, otherwise just 2 kV line to
earth, and using either plugable cords or
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