Agreed, but 'no breakdown' seems to be a vague term. Certainly, 100 mA
is a catastrophic breakdown, but is 10 µA 'breakdown'? I think it might
be, if the voltage (especially DC voltage) is applied for 1 minute. The
current may start at 10 µA, due to surface contamination, but then
increase as the insulation becomes tracked and degraded.
On 2026-03-14 13:22, Charlie Blackham wrote:
Brian
60335 isn’t well written in this regard in my opinion as it mixed two
completely different tests in the same clause
Clause 16.2 is a mains voltage earth leakage test done at 1.05x rated
voltage (similar to clause 5.7 in 62368-1)
This test has limits for “leakage current”, but there is also a
measurement circuit through which this current is measured.
Clause 16.3 is a Hipot withstand / Electric Strength test done with an
applied test voltage (similar to clause 5.4.9 in 62368-1)
This test has no limit on current -the only criteria being that no
breakdown will occur.
There a number of hipot testers available that will give 5kV ac/ 6kV
dc and 100 mA of leakage current for the 2^nd test – the 1^st test
needs a few passive components and a decent multimeter
Best regards
Charlie
**
*Charlie Blackham*
*Sulis Consultants Limited*
*Tel: +44 (0)7946 624317*
*Web: https://sulisconsultants.com/*
Registered in England and Wales, number 05466247
*From:*Brian Gregory <[email protected]>
*Sent:* 13 March 2026 23:12
*To:* [email protected]
*Subject:* [PSES] Fw: Re: [PSES] Dielectric test, electric appliances
Thanks for the replies, and Hi Doug!
Agreed, I can't think of an MOV worth buying that would survive a
1200-1400V dielectric test. We might install jumpers to bypass the
MOVs, and megger the completed boards.
Note I did find a copy of UL 60335-1 (3rd edition) and section 16.2
has current requirements. All below 1mA, except for 3.5 mA for
"STATIONARY CLASS I MOTOR-OPERATED APPLIANCES." which still sounds
low. There's a section stating that Class 1 Heating
appliances tripping current is 0.75 mA per kW of rating, which is more
in the ballpark.
Still very much a WIP.
happy weekend all,
Colorado Brian
---------- Forwarded Message ----------
From: Douglas Powell <[email protected]>
To: [email protected]
Subject: Re: [PSES] Dielectric test, electric appliances
Date: Fri, 13 Mar 2026 16:04:48 -0600
Richard,
I believe the MOV, or any type of protection, may offer some level of
surge protection; however, factors such as lead length will limit its
effectiveness, particularly concerning other parts of the mains
connection within the larger building. The primary goal is to have the
surge protection as close as possible to the equipment it is meant to
protect. In larger facilities, the line impedances and other
parasitics will significantly influence the protection results. From a
standards perspective, quantifying these factors is extremely challenging.
~Doug
Douglas E Powell
Founder & Principal Consultant
Vertex Compliance Consulting <https://bit.ly/45BXk3Y> (VertexCC)
Laporte, Colorado, USA
LinkedIn <https://www.linkedin.com/in/realdougpowell/>
Colorado Registered Business | Entity ID: 20191778678
(UTC-06:00, US-MDT)
On Fri, Mar 13, 2026 at 2:44 PM Richard Nute <[email protected]>
wrote:
Hi Derek:
I guess I am wrong about the MOV subjected to the hi-pot test.
Thanks for correcting me.
However… the MOV is there to protect the equipment from
overvoltage. Doesn’t it protect all equipment that is connected
to that branch circuit and ALL of the 120-volt premises system? I
think we only think of the immediate load. The MOV must protect
ALL of the distributed circuit, not just the load.
True?
Thanks, and best regards,
Rich
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