Joe,
I'm away from my data at present. I think IEC 62368-1 in clause 1
states that where a consistent connection to PE/ground cannot be
guaranteed, such as with pluggable equipment, protection from mains to
the PE requires to be a GDT and varistor to be connected in series.
Regards,
Mick Maytum
Safety and Telecom
Standards
mjmay...@gmail.com
www.ictsp-essays.info
------ Original Message ------
From: "Joe Randolph" <j...@randolph-telecom.com>
To: EMC-PSTC@listserv.ieee.org
Sent: 31/10/2017 02:09:14
Subject: [PSES] Regulatory requirements for MOVs placed line-to-ground
on AC mains ports?
Hello All:
Aside from surge tolerance during normal type testing, are there any
regulatory requirements regarding the placement of MOVs from line to
ground on an AC mains input port?
I seem to recall that some countries or standards are concerned about
potential hazards associated with MOVs developing high leakage current,
over time, in response to repeated surge events. I’ve seen circuits
where a GDT was added in series with the MOV, and I believe this had
something to do with concerns about MOV leakage current.
I’ve also seen MOVs offered for sale that are packaged in a way that
physically couples them to a thermally-activated one-time fuse. This
implies a concern with the MOV becoming leaky over time and
overheating.
While I am familiar with the potential failure mechanism of MOVs
developing high leakage current over time, I cannot point to any
published safety standard that imposes any construction requirements
that attempt to protect against this failure mode. I thought I
remembered seeing something on this topic many years ago in a UK
standard, but that was a long time ago, prior to harmonization of the
IEC 60950 series.
Thanks,
Joe Randolph
Telecom Design Consultant
Randolph Telecom, Inc.
781-721-2848 (USA)
j...@randolph-telecom.com
http://www.randolph-telecom.com
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