But does 60950-1 apply when the application is a door lock? In any
case, I am not suggesting that any particular power supply is
unreliable, but you never know what happens in installations and 'power
cross' is not an unknown hazard.
John Woodgate OOO-Own Opinions Only
J M Woodgate and Associates www.woodjohn.uk
Rayleigh, Essex UK
On 2017-11-22 18:09, Nyffenegger, Dave wrote:
In order for a power supply to meet SELV requirements it must pass all of the
tests in the EN60950-1 standard for SELV which means component failure testing
among other things, not simply isolation testing. Meanwell power supplies that
I have researched have been SELV. Meanwell has been very responsive if you
contact technical support and will provide the lab reports showing the power
supply passed the relevant SELV clauses in the standard.
If the power supply is UL approved the UL certificate available on the UL web
site may indicate whether or not it's SELV as well as power supply class and
other basic ratings.
-Dave
-----Original Message-----
From: Piotr Galka [mailto:piotr.ga...@micromade.pl]
Sent: Wednesday, November 22, 2017 12:51 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] Safe powering 12V doorlock
Dear safety experts,
Help me to make me sure that it is save to use the following power supply:
http://www.meanwell.com/webapp/product/search.aspx?prod=DRC-40
to power 12V doorlock with not earthed 12V supply.
I think that from practical point of view it is save but how it looks formally.
This supply is TUV EN60950-1 approved, and input to output is tested with
3kVAC. There is no info if output is SELV or ELV.
Before asking them if their output is SELV I'd like to know if it has to be
SELV, or if from info I have I can find it is SELV. I wont to use this case to
learn myself more about safety.
Why I'm not sure.
1. I suppose that 12 doorlock manufacturer can use only functional isolation
betwean 12V and its metal casing as he can assume (I think) that he gets safe
voltage.
If I'm wrong with it let me know.
2. Then as doorlock metal casing can be touched by user than 12V have to be
SELV circuit I think.
3. I'm not sure if the 12V output from this supply is SELV - is it enough to
test the isolation with 3kV.
In EN 60950-1:2006 5.2.2 I understand that if output is not grounded or there
is no protective screen than table 5C should be used.
I assume not earthing 12V.
I don't know if there is protective screen inside but as I can imagine such
supply there have to be feedback and it is probably opto feedback - so can
there be metal screen betwean LED and opto element and opto will work? I'm not
sure if I understand well what is screen in accordance with 2.6.1 e).
From Annex G I understand that for Overvoltage Category II transient voltage
(Europe) will be 2k5V and from table 5C I have 5kV test needed.
So 3kV written in datasheet looks being not enough.
All till now I have written assuming the Overvoltage Category II. But reading
Annex Z I'm not sure if access control system, as permanently installed, is
integral building wiring or not. It seems me more like a fuse panel then
permanently connected electric cooker. If category III then I end with 8kV
testing - much more than 3kV.
It is TUV approved and under Applications the producer lists Access Systems so
powering doorlock should be save. If it is true - where is my mistake.
Best Regards
Piotr Galka
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