In message <002101c9b6bf$ca409a50$d600a...@tamuracorp.com>, dated Mon, 6
Apr 2009, Brian O'Connell writes:
>When you refer to "mains circuits", does this mean the 'mains' power
>that enters the building, or is the individual distribution
>circuit/node being reference ?
>
>Do you mean that a fu
reaker ?
thanks,
Brian
> -Original Message-
> From: emc-p...@ieee.org [mailto:emc-p...@ieee.org]On Behalf Of John
> Woodgate
> Sent: Monday, April 06, 2009 1:47 AM
> To: Piotr Galka
> Cc: EMC-PSTC
> Subject: Re: PoE injectors
>
> In message <79BF8E9B82E1434482
John,
- Original Message -
From: "John Woodgate"
> I explained that if there is accidental contact between an SELV circuit in
> a building and a power circuit, the SELV circuit can go to, and remain
> indefinitely at, full mains voltage.
Everything clear.
I didn't considered such sce
In message <79BF8E9B82E143448258D4EBCD718037@MmPc21>, dated Mon, 6 Apr
2009, Piotr Galka writes:
>In my opinion in such installations SELV gives less risk of electric
>shock
I explained that if there is accidental contact between an SELV circuit
in a building and a power circuit, the SELV cir
John,
- Original Message -
From: "John Woodgate"
>
> In most countries, that technique (TN-C-S) is used only if the combined
> neutral and grounded conductor is grounded at many places, so that if it
> breaks, load current is distributed among the grounding points and remains
> at saf
In message <00AEA30D28014979B44664EAB0477931@MmPc21>, dated Sat, 4 Apr
2009, Piotr Galka writes:
>Consider electric installation with zeroing and not grounding. I'm not
>sure how it is in another countries so to be precise grounding is the 3
>wire installation, and zeroing is the 2 wire instal
afely then isolated and grounded (if
grounded is understand as connected to socket grounding pin).
But I'm certainly not an expert in safety issues.
Best Regards
Piotr Galka
- Original Message -
From: "John Woodgate"
To:
Sent: Friday, March 27, 2009 9:39 AM
Subject: Re:
In message , dated Sat, 28 Mar 2009,
John Woodgate writes:
>I don't think I came even close to making that mistake.
Oops! I misread your message. I thought you were referring to multiple
grounds on the POE cable.
What I see you DO mean is that if there is a mains-to-POE short at a
long dista
In message <49cd7a6d.3020...@itesafety.com>, dated Fri, 27 Mar 2009,
Robert Johnson writes:
>Earthing the output of a power source is one way of preventing faults
>within the source between mains to output from energizing the output.
>It quickly overloads and opens the mains circuit.
Indeed.
Hi, Joe.
On 27 Mar 2009 at 0:59, Joe Randolph wrote:
>
> On 3/26/2009, Peter Tarver wrote:
>
> > What if the power supply is Class 2 Equipment?
>
> Hi Pete:
>
> A Class 2 supply is the most common type of supply that I
> have seen for POE injection. And yes, the output should be
> isolated fro
Earthing the output of a power source is one way of preventing faults within
the source between mains to output from energizing the output. It quickly
overloads and opens the mains circuit.
Relying on an earthing for protection of a signal circuit which runs any
distance from the source to protect
In message <6.1.0.6.2.20090327120836.030f3...@pop.randolph-telecom.com>,
dated Fri, 27 Mar 2009, Joe Randolph writes:
>I will try to explain the mechanism, but I don't want to take this
>thread too far off track.
OK, I've replied off-list.
--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk
On 3/27/2009, John Woodgate wrote:
How can Y-caps do that? Y caps go from both mains poles to earth.
Hi John:
I will try to explain the mechanism, but I don't want to take this thread too
far off track. Most of the discussion here has been about the safety aspects
of POE. My comm
In message
<201048ea81ba0745aca78e4cc883900104781...@desmdswms201.des.grplnk.net>,
dated Fri, 27 Mar 2009, "Haynes, Tim (SELEX GALILEO, UK)"
writes:
>Does this change the circuit for SELV to PELV and I thought that PELV
>and SELV circuits could not be "mixed and matched" as the SELV circuit
John, All,
I know nothing about PoE or IT systems as such but...
>Grounding the chassis of the POE injector fixes the problem, but most
>of these devices are ungrounded.
Does this change the circuit for SELV to PELV and I thought that PELV
and SELV circuits could not be "mixed and matched" as
In message <6.1.0.6.2.20090327004517.030f4...@pop.randolph-telecom.com>,
dated Fri, 27 Mar 2009, Joe Randolph writes:
>A Class 2 supply is the most common type of supply that I have seen for
>POE injection. And yes, the output should be isolated from earth
>ground to comply with IEEE 802.3af.
On 3/26/2009, Peter Tarver wrote:
What if the power supply is Class 2 Equipment? Then the
isolation requirements are somewhat larger than 1500 V.
Also, doesn't the supplied power to the PD have to continue
to be isolated from earth, as do the ethernet circuit
On 25 Mar 2009 at 21:47, neve...@comcast.net wrote:
>
> Does it matter for the discussion that:
>
> 1) Power is not present at the output of the source unless
> the other side of the cable connects to a PD (powered
> device) which "signals" to the sourcing equipment it is a PD
> and to turn it on
On 26 Mar 2009 at 9:00, Umbdenstock, Don wrote:
>
> My apologies for thinking out loud “if a PD can present up
> to a 13 W load, then the 25k handshake cannot be part of the
> load, but rather is restricted to a handshake circuit. So
> the question is whether there is a spec for current limiting
>
On 25 Mar 2009 at 23:17, Ron Pickard, RPQ wrote:
>
> Hi Don,
>
> Further to what Joe has stated below, according to IEC
> 60950-1 an ethernet interface circuit is generally
> characterized as an SELV circuit, but must also be
> considered a TNV-1 circuit if it is subject to overvoltages
> (atmosp
The power supply in the sourcing equipment are isolated per IEEE 802.3
(1500Vrms).
?
Neven
From: "Don Umbdenstock"
To: emc-p...@ieee.org
Sent: Wednesday, March 25, 2009 1:42:50 PM GMT -08:00 US/Canada Pacific
Subject: RE: PoE injectors
Let me share some of my thought process wit
t.law...@slpower.com [mailto:pat.law...@slpower.com]
Sent: Wednesday, March 25, 2009 12:14 PM
To: Umbdenstock, Don
Cc: emc-p...@ieee.org
Subject: Re: PoE injectors
Hi Don,
What does 'LPS' mean in this context?
Pat Lawler
EMC Engineer
SL Power Electronics Corp.
"Umbdenstock, Don" wr
On 3/25/2009, Don Umbdenstock wrote:
I have perused the IEEE 802.3af explanation on various web sites and
examined
supplier specs. I came to the conclusion that the injector should be LPS
certified and marked as such. However, most of the injectors I have found by
web search do not in
com/>
www.linkedin.com/in/RonPickard
From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Joe Randolph
Sent: Wednesday, March 25, 2009 9:20 PM
To: Umbdenstock, Don; emc-p...@ieee.org
Subject: Re: PoE injectors
On 3/25/2009, Don Umbdenstock wrote:
...@ieee.org
Subject: Re: PoE injectors
Does it matter for the discussion that:
1) Power is not present at the output of the source unless the other side of
the cable connects to a PD (powered device) which "signals" to the sourcing
equipment it is a PD and to turn it on. If you unplug the PD,
A primary question in the US is: Does the circuit qualify as a Class 2 (or
Class 3) circuit according to the National Electrical Code? (ref: NFPA 70
clause 725.121) If it fails to qualify, then wiring requirements become quite
stringent.
There are seven possibilities: a listed Class 2 transformer,
I gave a presentation to the Santa Clara Valley chapter of
the PSES in JUN2007 that has guidance on this topic. Find
it at:
http://www.ewh.ieee.org/r6/scv/pses/ieee_scv_pses_jun07.pdf
(My follow-up presentation from FEB2008 is extraordinarily
delinquent in being posted, due to s/w issues at m
440
From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Umbdenstock,
Don
Sent: Thursday, March 26, 2009 8:44 AM
To: neve...@comcast.net; emc-p...@ieee.org
Subject: RE: PoE injectors
I understand that most typical circuits present less than 1k Ohm or upwards of
Meg Ohm load,
O'Connell
> Sent: Wednesday, March 25, 2009 10:26 AM
> To: emc-p...@ieee.org
> Subject: RE: PoE injectors
>
> Limited Power Source - q.v., 2.5 and 6 of UL60950-1
>
> Power on TNV wiring to a remote device cannot be considered LPS.
>
> > -Origina
:14 AM
> To: Umbdenstock, Don
> Cc: emc-p...@ieee.org
> Subject: Re: PoE injectors
>
> Hi Don,
>
> What does 'LPS' mean in this context?
>
> Pat Lawler
> EMC Engineer
> SL Power Electronics Corp.
>
> "Umbdenstock, Don" wr
Hi Don,
What does 'LPS' mean in this context?
Pat Lawler
EMC Engineer
SL Power Electronics Corp.
"Umbdenstock, Don" wrote on 03/25/2009
07:23:54 AM:
> I have perused the IEEE 802.3af explanation on various web sites and
> examined supplier specs. I came to the conclusion that the injector
> s
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