Hi Bostjan,
Previously I looked in definitions list in alphabetic order and there is
no SECONDARY CIRCUIT (in Polish adoption of not translated standard).
But looking in not alphabetic I found it and I see my 12V is the
SECONDARY CIRCUIT.
If the sentence I cited previously refers to products powered by
secondary circuit (for example my 12V) I think It should be written more
clearly. It should be not "for SECONDARY CIRCUIT" but "for devices
powered by SECONDARY CIRCUIT" or something like this.
I remember someone told me here (I think 8..10 years ago) that literally
understanding the 60950-1 I am right, but practice is different. I think
it was about varistor crossing the isolation in my device powered from 12V.
It looks it is the second such situation.
Best Regards
Piotr
W dniu 2017-11-23 o 13:46, Boštjan Glavič pisze:
Hi Piotr,
This refers to products supplied by secondary circuit. Power supply is supplied
by AC mains therefore primary circuit. For OVC II we always apply 5B. You can
trust me on this since we approve many power supplies.
Best regards,
Bostjan
-----Original Message-----
From: Piotr Galka [mailto:piotr.ga...@micromade.pl]
Sent: Thursday, November 23, 2017 1:25 PM
To: Boštjan Glavič <bostjan.gla...@siq.si>; EMC-PSTC
<emc-pstc@listserv.ieee.org>
Subject: Re: [PSES] Safe powering 12V doorlock
Hi Bostjan,
In 5.2.2 there is the sentence: "However, for a SECONDARY CIRCUIT that is neither
connected to protective earth nor provided with a protective screen in accordance with
2.6.1 e), Table 5C shall be used."
I understand that, that way it depends on output which table to select.
In Definitions I don't see SECONDARY CIRCUIT but I understand 12V as being here
SECONDARY CIRCUIT.
As it is (can be) not connected to earth and I don't know of protective screen
I'm not sure - may be 5C applies.
Beast Regards
Piotr
W dniu 2017-11-23 o 05:49, Boštjan Glavič pisze:
Hi Piotr,
I agree with Rich.
According to specification, output also complies with LPS (Limited Power
Source) therefore output must be SELV.
There is no PELV definition in IEC 60950-1.
About table 5B or 5C, which table you will use does not depend on output from your
power supply but on mains voltage (main network system). For normal application we
are using STAR system with 230V L to N voltage with OVC II --> you can use
table 5B.
Table 5C is used for OVC III applications.
I hope this helps.
Best regards,
Bostjan
-----Original Message-----
From: Richard Nute [mailto:ri...@ieee.org]
Sent: Thursday, November 23, 2017 2:28 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Safe powering 12V doorlock
Hi Piotr:
The easy way to answer your questions is to request a copy of the TUV report.
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.
Yes, only functional insulation between the 12 volts and the metal casing.
2. Then as doorlock metal casing can be touched by user than 12V have to be
SELV circuit I think.
Yes. SELV or PELV; makes no difference.
3. I'm not sure if the 12V output from this supply is SELV - is it enough to
test the isolation with 3kV.
No, 3 kV alone is not sufficient. The isolation must also meet creepage and
clearance distances after being subject to a mechanical test of the isolation
means and the conductors.
Best regards,
Rich
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