I read in !emc-pstc that Gary McInturff gmcintu...@spraycool.com wrote
(in 9f347458edacb64b8ff57db67e6e0faa6ec...@cerebrum.spraycool.com)
about 'How do I do this test?' on Tue, 9 Dec 2003:
There is another example of class I and class II insulations in
parallel that may be sitting on your desk
the same thing may happen
for non-grounded SELV circuits. (There are some EMC concerns with this
construction as well).
Gary
From: John Woodgate [mailto:j...@jmwa.demon.co.uk]
Sent: Monday, December 08, 2003 10:21 PM
To: emc-p...@majordomo.ieee.org
Subject: Re: How do I do this test?
I read
I read in !emc-pstc that Rich Nute ri...@sdd.hp.com wrote (in
200312090134.raa09...@epgc264.sdd.hp.com) about 'How do I do this
test?' on Mon, 8 Dec 2003:
My comment was to suggest that such crosses within the walls and
ceilings of homes in the USA are rare,
I'm not really addressing homes
I read in !emc-pstc that Rich Nute ri...@sdd.hp.com wrote (in
200312082301.paa09...@epgc264.sdd.hp.com) about 'How do I do this
test?' on Mon, 8 Dec 2003:
Hi John:
For professional audio, it's common to design to Class II requirements
and then add an earthed screen in the mains or SMPS
I read in !emc-pstc that Rich Nute ri...@sdd.hp.com wrote (in
200312082248.oaa08...@epgc264.sdd.hp.com) about 'How do I do this
test?' on Mon, 8 Dec 2003:
Hi John:
But what it is really NOT to be used for is anything that has wiring
installed in the walls and/or ceiling voids
John,
Yes, I'm working late this morning!
Of course, in the event of a power cross between the telecommunications
network and mains then any ICT equipment connected to that telecommunications
network should remain safe due to the power-cross test required in UL 60950
(but not required by the
Hi Richard:
My, you are working late tonight!
Sorry to contradict you but...
1) Agreed that doorbells operate at ELV and are typically double insulated
from mains circuits. Some standards would even call this SELV grin.
I don't believe you have contradicted me here.
2)
Rich,
Sorry to contradict you but...
1) Agreed that doorbells operate at ELV and are typically double insulated
from mains circuits. Some standards would even call this SELV grin.
2) The ringing voltage for a domestic telephone (POTS) is above the ELV
limits. When such a Telecommunications
Hi John:
For professional audio, it's common to design to Class II requirements
and then add an earthed screen in the mains or SMPS isolating
transformer, and a user option to connect signal common to the PEC or
not.
This seems to bring us full circle, back to
the original
Hi John:
But what it is really NOT to be used for is anything that has wiring
installed in the walls and/or ceiling voids. This wiring is very
vulnerable to accidental contact with mains wiring when the building is
being altered, painted etc.
In the USA, we violate this
I read in !emc-pstc that Rich Nute ri...@sdd.hp.com wrote (in
200312081902.laa08...@epgc264.sdd.hp.com) about 'How do I do this
test?' on Mon, 8 Dec 2003:
Do you advise against the use of Class II construction for this reason?
Class II is OK for TVs that have no connectors or only isolated
John,
The Hazard Based Standard is still in the early stages of development within
the IEC, so there will be many changes before a document is available for
public comment. Many of the individuals participating in the development work
for well known manufacturers while others work for certain
Hi John:
My understanding is that IEC 60950 uses a definition of 'SELV' that
allows it to be earthed, whereas other standards require that SELV is
NOT earthed but floating. IMHO, the latter is dangerous because an
undetected fault can put that floating SELV circuit at a hazardous
Richard
From: richhug...@aol.com [mailto:richhug...@aol.com]
Sent: 08 December 2003 17:36
To: john.al...@era.co.uk; j...@jmwa.demon.co.uk; emc-p...@majordomo.ieee.org
Subject: Re: How do I do this test?
In a message dated 08/12/2003 16:45:59 GMT Standard Time, john.al...@era.co.uk
writes
In a message dated 08/12/2003 16:45:59 GMT Standard Time, john.al...@era.co.uk
writes:
Richard
Not to carp too much, but your first para sounds like the proverbial company
make over whereby you reorganise the management in theory, but make no real
changes in practice!
I see no reason to
Subject: Re: How do I do this test?
John,
You may be pleased to know that the Hazard Based Standard that is being
developed to replace both IEC 60950-1 and IEC 60065 does not use the term SELV
(or PELV) but invents a whole new set of abbreviations.
Of course, within IEC 60950-1 the correct
John,
You may be pleased to know that the Hazard Based Standard that is being
developed to replace both IEC 60950-1 and IEC 60065 does not use the term SELV
(or PELV) but invents a whole new set of abbreviations.
Of course, within IEC 60950-1 the correct usage of the term is not 'SELV' but
do I do this test?
I read in !emc-pstc that Rich Nute ri...@sdd.hp.com wrote (in
200312051737.jaa27...@epgc264.sdd.hp.com) about 'How do I do this
test?' on Fri, 5 Dec 2003:
At one time, using SELV earthing as a
supplementary protection scheme was not
allowed in some countries
I read in !emc-pstc that Rich Nute ri...@sdd.hp.com wrote (in
200312051737.jaa27...@epgc264.sdd.hp.com) about 'How do I do this
test?' on Fri, 5 Dec 2003:
At one time, using SELV earthing as a
supplementary protection scheme was not
allowed in some countries. I'm not sure
Hi John:
The construction you describe has two insulations in parallel:
1) basic insulation between mains and earth, and
2) double insulation between mains and earthed SELV.
Since the insulations are in parallel, the basic insulation must be
disconnected in
to which the
earthed SELV is bonded.
Regards
Vic
From: John Woodgate [mailto:j...@jmwa.demon.co.uk]
Sent: 04 December 2003 21:20
To: emc-p...@majordomo.ieee.org
Subject: Re: How do I do this test?
I read in !emc-pstc that Rich Nute ri...@sdd.hp.com wrote (in
200312012224.oaa12...@epgc264
I read in !emc-pstc that Rich Nute ri...@sdd.hp.com wrote (in
200312012224.oaa12...@epgc264.sdd.hp.com) about 'How do I do this
test?' on Mon, 1 Dec 2003:
The construction you describe has two insulations in parallel:
1) basic insulation between mains and earth, and
2) double
Hi Vic:
I have a Class 1 product. It has a double insulation barrier between
Primary
and earthed SELV, and basic between primary and the metal enclosure.
How can I perform an electrical strength test across the primary/SELV
barrier?
The construction you describe has two
Vic,
As always, the Devil's in the detail...
You are correct in thinking that the requirement is Basic Insulation from a
primary circuit and protective earth. However, in this case the 'earthed
part' must meet all the requirements of clause 2.6 (if the base standard is
taken to be IEC 60950-1).
...@e2vtechnologies.com]
Sent: 01 December 2003 11:27
To: EMC-PSTC (E-mail)
Subject: How do I do this test?
Good morning,
I have a Class 1 product. It has a double insulation barrier between Primary
and earthed SELV, and basic between primary and the metal enclosure.
How can I perform an electrical
Good morning,
I have a Class 1 product. It has a double insulation barrier between Primary
and earthed SELV, and basic between primary and the metal enclosure.
How can I perform an electrical strength test across the primary/SELV
barrier?
I believe I must disconnect the 'earthed' connection -
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