Ned, John, and EMC-Pstc
Thanks for your responses. You almost convinced me (at least you started
to) but the standard is either so badly written that it still could be
interpreted multiple ways or it is using different terminology than the
standards you are using. Let me elaborate a little more.
The table I am most concerned with (Table 23) will serve as an example of
the others and if I can come to a good understanding of it, I'll understand
the remainder of the document. This may be old news to all of you but let
me quote paragraph 1.4.26 which defines the four levels of insulation:
1) basic insulation: Insulation applied to live parts to provide basic
protection against electric shock.
2) supplementary insulation: Independent insulation applied in addition to
basic insulation in order to ensure protection against electric shock in the
event of a failure of the basic insulation.
3) double insulation: Insulation comprising both basic insulation and
supplementary insulation.
4) reinforced insulation: Single insulation system applied to live parts
which provides a degree of protection against electric shock equivalent to
double insulation under the conditions specified in this standard.
Table 23 is as follows:
Table 23 - Minimum creepage distances for printed wiring boards (Basic and
supplementary)
CIRCUIT Protective Uncoated Uncoated
VOLTAGE Coating Pollution Pollution
Degree 1 Degree 2
----------------------------------------------------------------------------
----------
0-50 0.025 0.025 0.04
50-100 0.1 0.1 0.16
100-160 0.25 0.25 0.4
160-320 0/75 0.75 1.6
As you can see, there is only one value for "Basic and supplementary
insulation". This clause is exactly as it appears in the definition of
double insulation. The table does not provide one number for Basic
insulation and another number for supplementary insulation. Thus I conclude
these numbers are for the combined Basic and supplementary insulation, which
is, by definition, double insulation. Please correct me if I'm wrong. How
do these creepage numbers stack up against the standards you use for the
same voltages? Shouldn't they be the same?
Also note, there is a column for protective coating and another for
pollution degree 1. If they meant for these two to mean the same thing, I
would think they would have only one column for pollution degree
1/protective coating. Furthermore, referencing the definitions for the
pollution degrees, pollution degree 1 says nothing about coating but does
talk about dry, non-conductive pollution - again, it says nothing about
coatings and nothing about hermetically sealed containers. How does your
standards read regarding the degrees of pollution?
As you can see, I'm still confused. Are the pollution degrees and types of
insulation intended to be universal within all European Norms? If so, where
does it say so and where does it give the definitive reading of each?
Again, I appreciate your feedback. I've seen many instances where members
of this group have commented on the extreme value they have received from
information gained within. I too, have to tell all of you. I would be in
total darkness without your insight.
Thanks,
Dan Kinney
Horner APG
> -----Original Message-----
> From: Ned Devine [SMTP:ndev...@entela.com]
> Sent: Wednesday, December 20, 2000 2:19 PM
> To: Emc-Pstc (E-mail)
> Subject: RE: creepage distances (EN61131-2)
>
>
> Dan,
>
> I don't have access to EN61131-2, but I think you may of misinterpreted
> the
> standard. I believe that for double/reinforced insulation you will need
> two
> times the values in table for basic/supplementary insulation. Also, your
> product is Pollution degree 2 and not 1.
>
> In general, there is a table for Basic/supplementary and different table
> for
> double/reinforced. But in some standards, they just say that the
> requirement for double/reinforced is twice the values in the table for
> basic/supplementary. This comes from the fact that double insulation is
> defined as basic PLUS supplementary. Therefore twice the value for a
> single
> basic/supplementary insulation.
>
> Pollution degree 1 is generally for potted or otherwise sealed components
> only. Normal products are pollution degree 2.
>
> Ned Devine
> Entela, Inc.
> Program Manager III
> Phone 616 248 9671
> Fax 616 574 9752
> e-mail ndev...@entela.com
>
>
>
> -----Original Message-----
> From: Dan Kinney (A) [mailto:dan.kin...@heapg.com]
> Sent: Wednesday, December 20, 2000 12:03 PM
> To: Emc-Pstc (E-mail)
> Subject: creepage distances (EN61131-2)
>
>
>
> I know most of you don't use EN61131-2 (Safety for Programmable
> Controllers
> but I'm hoping the questions I have can be answered in general terms. And
> if anyone does have/use EN61131-2, I provide paragraph and table reference
> numbers.
>
> This is a very convoluted and confusing standard but I think we have
> looked
> at the creepage and clearance section long enough that we finally have it
> figured out. But before I commit to something, I'd like confirmation from
> this group. The standard provides definitions for basic, supplementary,
> double, and reinforced insulation (paragraph 1.4.26). It also provides a
> general rule of thumb, worst case creepage and clearance table for basic
> and
> supplementary insulation (paragraph 4.3 subparagraph 3) and its table). I
> interpret this to mean, if I use these very conservative creepages and
> clearances, I more than meet anything presented later in the standard. I
> also interpret this to mean the numbers within this table provide double
> insulation since the definition of double insulation is basic and
> supplementary insulation combined.
>
> The standard then provides several tables of creepage and clearances under
> very specific conditions that includes material types and pollution
> degrees.
> The one I'm most concerned with is the table for basic and supplementary
> creepage distances for printed wiring boards (Table 23). As with the
> previous paragraph, I interpret this to mean double insulation.
>
> The standard provides definitions for pollution degrees (paragraph
> 1.4.42).
> It says:
> Pollution degree 1: No pollution or only dry, non-conductive pollution
> occurs. The pollution has no influence.
> Pollution degree 2: Normally, only non-conductive pollution occurs.
> Occasionally, however, a temporary conductivity caused by condensation
> shall
> be expected.
> Pollution degree 3: Conductive pollution occurs, or dry, non-conductive
> pollution occurs which becomes conductive due to condensation which is
> expected.
>
> Our products, are intended for industrial or commercial environments and
> are
> specified to be mounted in a metal enclosure where pollutants are sealed
> out. Further our specifications clearly state our products work 5% to 95%
> non-condensing relative humidity. Thus I interpret the standard to mean
> our
> products should be evaluated under pollution degree 1.
>
> Lastly, paragraph 4.3.4 states creepage distances for reinforced
> insulation
> "shall be double the value for basic insulation". I interpret this
> paragraph to be non-applicable to the work we are doing since all the
> tables
> list basic and supplementary (double) creepage and clearance distances.
> It
> does not list basic creepage and clearances individually and thus I have
> nothing to double. But by using the values provided in the tables, I meet
> double insulation requirements.
>
> I apologize for this lengthy message. And I apologize if I haven't
> provided
> enough information to understand the situation. As I said, this is very
> confusing for we, the uninitiated. My questions center around my
> interpretations and can be distilled down to one question; have I
> interpreted each point above correctly? Any advice, general or specific,
> will be greatly appreciated.
>
> Happy Holidays all.
>
> Dan Kinney
> Horner APG
>
>
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