The UL “Dielectric Voltage Withstand Test” is well written and it
supports the premise that leakage current shall not be a failure
criterion during a type or routine hipot test.
I will only point out that capacitance leakage is a misnomer. It is
the easily predicted capacitive reactance which causes current during
a.c. hipot.
Leakage implies current via the resistance of the dielectric material
in a Y-rated capacitor. That leakage current should be miniscule even
at a dielectric test voltage level. (e.g. << 1 uA ) However, the
reactive current could easily be > 10 mA during a.c. hipot and why
d.c. tests are often preferable.
Ralph
*From:*Scott Aldous <[email protected]>
*Sent:* March 13, 2026 9:06 AM
*To:* [email protected]
*Subject:* Re: [PSES] Dielectric test, electric appliances
Hi Brian,
You might find the paper at this link
<https://share.google/TD5B7y1z6kcLqK8Gj> interesting. So apparently
there are some standards that reference a max leakage current limit
for the test. UL also has a paper with a good discussion of the
current limit here
<https://code-authorities.ul.com/wp-content/uploads/sites/40/2015/02/UL_WP_Final_The-Dielectric-Voltage-Withstand-Test_v5_HR.pdf>.
On Fri, Mar 13, 2026 at 5:37 AM James Hulbert
<[email protected]> wrote:
An MOV (or similar) needs to be removed if its clampling voltage
is less than the hipot test voltage.
Jim Hulbert
*From:*Ralph McDiarmid <[email protected]>
*Sent:* Thursday, March 12, 2026 6:02 PM
*To:* [email protected]
*Subject:* Re: [PSES] Dielectric test, electric appliances
This message is from an *EXTERNAL EMAIL* system. Use caution and
think before opening attachments, clicking links, or responding.
Traditionally, dielectric strength (hipot) tests were done only to
verify clearance. Now, the industry seems to think there is
figure of merit associated with leakage current in solid
insulation during that test. There are other tests which can be
performed to verify the integrity of solid insulation.
As Rich points out, the pass/fail criterion of a hipot test is
breakdown/flashover of the air (a spark) which should trip a
properly designed tester.
If not removed or otherwise isolated from the hipot test, a MOV or
a GDT will likely trip the tester by their excessive leakage
current. Y1 and Y2 capacitors should not cause a trip and can be
left in circuit during the test unless their reactance presents a
difficulty. Most standards will permit a d.c. test voltage in lieu
of an a.c. test.
Ralph
*From:*Richard Nute <[email protected]>
*Sent:* March 12, 2026 2:43 PM
*To:* [email protected]
*Subject:* Re: [PSES] Dielectric test, electric appliances
Hi Brian:
The hi-pot (dielectric withstand) test is to verify that the power
line solid insulations and air insulations (clearances) to ground
will withstand (without breakdown) the transient voltages coming
in on the power lines.
The hi-pot tester (ac) must provide sufficient current to the
Y-caps to achieve the required test voltage. You can calculate
the test current from the leakage current, as the test current is
simply a voltage multiple of the leakage current voltage. (You
can use a dc hi-pot tester, at the peak of the ac test voltage,
but there still will be current due to the rate of voltage rise
charging the Y-caps.)
Duration of the hi-pot test usually is one minute, but need only
be a few seconds as ionization of air only takes a few seconds. I
assume your solid insulation has more than adequate dielectric
strength, so air insulation (clearance) is more likely to fail.
Y-caps and MOVs are rated to withstand the hi-pot test. They have
to withstand the transient voltages in service! They do not need
to be removed during the hi-pot test.
Pass criterion is very simple: No breakdown! If a breakdown
occurs, you can hear it! And, a good hi-pot tester will shut down
and sound an alarm.
The hi-pot test tests the entire primary insulation between mains
and ground. From power input to the isolation to grounded
secondary (if any).
Good luck!
Rich
*From:*Brian Gregory <[email protected]>
*Sent:* Thursday, March 12, 2026 12:54 PM
*To:* [email protected]
*Subject:* [PSES] Dielectric test, electric appliances
Hello safety colleagues,
We are looking at some changes for End of Line dielectric test for
a 240-V rated residential appliance - not medical! - for N.
American residential applications.
Interestingly, the appropriate UL standards detail test voltages
and duration, are a bit vague about legal removal of solid state
components "that are capable of being damaged" and absolutely
silent on the level of allowable leakage current. I have looked
at 3 different safety standards for north american products, and
not one specifies a failure limit. This includes the main BESS/PV
inverter standard, UL 1741, which is typically very precise.
Past experience at an NRTL involved setting the HiPot to 5 or
perhaps 10 mA for the test, but I can't remember what mandated the
successful test level. My friendly AI bot a few weeks ago
suggests 3.5 or 5 mA as allowable for residential appliances, but
not what requirement(s) there may be apart from perhaps 60335. UL
60335 is not cited in any of the product safety standards that
cover our current products. That same bot is now telling me 100 mA
is allowed during dielectric withstand testing. So, if we can
find a HiPot tester with 100mA or more capacity, we can speed up
our production line by not having to remove Y-caps and/or MOVs, or
go to the 1-second test levels, or both, and still get a base
level check that a board's insulation system wasn't compromised
during production or assembly.
This brings up some interesting questions as we evaluate bringing
up a new production line.
- is there an actual requirement for the mA draw, or is it just
what one can find in a hipot device? The testers we've bought &
rented stop at 10 or 20 mA.
- are there stated mA limits for dielectric breakdown detection?
If the bot is right and 60335 is correct, what's the specific clause?
- is there anything besides board level defects the dielectric
test is supposed to catch?
- could one include calculations for mA draw from a device's
Y-caps and/or MOVs in an allowable EoL test plan, in case the
inspector doesn't trust some chinese-made hipot with 200 mA
capacity and asks us to justify a given limit?
thanks all, stay safe.
Colorado Brian
------------------------------------------------------------------------
This message is from the IEEE Product Safety Engineering Society
emc-pstc discussion list. To post a message to the list, send your
e-mail to [email protected]
All emc-pstc postings are archived and searchable on the web at:
https://www.mail-archive.com/[email protected]/
<https://urldefense.com/v3/__https:/www.mail-archive.com/[email protected]/*20__;JQ!!GXa4NB5MBjHR!RmueCI4FlV1mH69AOn7nYGgUA9MhgKXVfW_R4rHTCo5Dpa2kdNe463sWy9yGB9looSb0B4i1GvBwcXXxQ-PKHfrJSp0$>
Website: https://ewh.ieee.org/soc/pses/
<https://urldefense.com/v3/__https:/ewh.ieee.org/soc/pses/__;!!GXa4NB5MBjHR!RmueCI4FlV1mH69AOn7nYGgUA9MhgKXVfW_R4rHTCo5Dpa2kdNe463sWy9yGB9looSb0B4i1GvBwcXXxQ-PKe9GsUb4$>
Instructions: https://ewh.ieee.org/soc/pses/list.html (including
how to unsubscribe)
<https://urldefense.com/v3/__https:/ewh.ieee.org/soc/pses/list.html__;!!GXa4NB5MBjHR!RmueCI4FlV1mH69AOn7nYGgUA9MhgKXVfW_R4rHTCo5Dpa2kdNe463sWy9yGB9looSb0B4i1GvBwcXXxQ-PKVMJ7zdU$>
List rules:
https://pses.ieee.org/wp-content/uploads/2024/12/EM-PSTC-List-Rules.pdf
<https://urldefense.com/v3/__https:/pses.ieee.org/wp-content/uploads/2024/12/EM-PSTC-List-Rules.pdf__;!!GXa4NB5MBjHR!RmueCI4FlV1mH69AOn7nYGgUA9MhgKXVfW_R4rHTCo5Dpa2kdNe463sWy9yGB9looSb0B4i1GvBwcXXxQ-PKhTeIvJQ$>
For help, send mail to the list administrators:
Mike Sherman at: [email protected]
Rick Linford at: [email protected]
For policy questions, send mail to:
Jim Bacher at: [email protected]
------------------------------------------------------------------------
To unsubscribe from the EMC-PSTC list, click the following link:
https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1
<https://urldefense.com/v3/__https:/listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1__;!!GXa4NB5MBjHR!RmueCI4FlV1mH69AOn7nYGgUA9MhgKXVfW_R4rHTCo5Dpa2kdNe463sWy9yGB9looSb0B4i1GvBwcXXxQ-PKQjN_NIs$>
------------------------------------------------------------------------
This message is from the IEEE Product Safety Engineering Society
emc-pstc discussion list. To post a message to the list, send your
e-mail to [email protected]
All emc-pstc postings are archived and searchable on the web at:
https://www.mail-archive.com/[email protected]/
<https://urldefense.com/v3/__https:/www.mail-archive.com/[email protected]/__;!!GXa4NB5MBjHR!RmueCI4FlV1mH69AOn7nYGgUA9MhgKXVfW_R4rHTCo5Dpa2kdNe463sWy9yGB9looSb0B4i1GvBwcXXxQ-PK7-ohBmU$>
Website: https://ewh.ieee.org/soc/pses/
<https://urldefense.com/v3/__https:/ewh.ieee.org/soc/pses/__;!!GXa4NB5MBjHR!RmueCI4FlV1mH69AOn7nYGgUA9MhgKXVfW_R4rHTCo5Dpa2kdNe463sWy9yGB9looSb0B4i1GvBwcXXxQ-PKe9GsUb4$>
Instructions: https://ewh.ieee.org/soc/pses/list.html (including
how to unsubscribe)
<https://urldefense.com/v3/__https:/ewh.ieee.org/soc/pses/list.html__;!!GXa4NB5MBjHR!RmueCI4FlV1mH69AOn7nYGgUA9MhgKXVfW_R4rHTCo5Dpa2kdNe463sWy9yGB9looSb0B4i1GvBwcXXxQ-PKVMJ7zdU$>
List rules:
https://pses.ieee.org/wp-content/uploads/2024/12/EM-PSTC-List-Rules.pdf
<https://urldefense.com/v3/__https:/pses.ieee.org/wp-content/uploads/2024/12/EM-PSTC-List-Rules.pdf__;!!GXa4NB5MBjHR!RmueCI4FlV1mH69AOn7nYGgUA9MhgKXVfW_R4rHTCo5Dpa2kdNe463sWy9yGB9looSb0B4i1GvBwcXXxQ-PKhTeIvJQ$>
For help, send mail to the list administrators:
Mike Sherman at: [email protected]
Rick Linford at: [email protected]
For policy questions, send mail to:
Jim Bacher at: [email protected]
------------------------------------------------------------------------
To unsubscribe from the EMC-PSTC list, click the following link:
https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1
<https://urldefense.com/v3/__https:/listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1__;!!GXa4NB5MBjHR!RmueCI4FlV1mH69AOn7nYGgUA9MhgKXVfW_R4rHTCo5Dpa2kdNe463sWy9yGB9looSb0B4i1GvBwcXXxQ-PKQjN_NIs$>
This email message may contain confidential, proprietary and/or
privileged information. It is intended only for the use of the
intended recipient(s). If you have received it in error, please
immediately advise the sender by reply email and then delete this
message. No one other than the intended recipient may disclose,
copy, distribute or use the information contained in this message.
------------------------------------------------------------------------
This message is from the IEEE Product Safety Engineering Society
emc-pstc discussion list. To post a message to the list, send your
e-mail to [email protected]
All emc-pstc postings are archived and searchable on the web at:
https://www.mail-archive.com/[email protected]/
Website: https://ewh.ieee.org/soc/pses/
Instructions: https://ewh.ieee.org/soc/pses/list.html (including
how to unsubscribe) <https://ewh.ieee.org/soc/pses/list.html>
List rules:
https://pses.ieee.org/wp-content/uploads/2024/12/EM-PSTC-List-Rules.pdf
For help, send mail to the list administrators:
Mike Sherman at: [email protected]
Rick Linford at: [email protected]
For policy questions, send mail to:
Jim Bacher at: [email protected]
------------------------------------------------------------------------
To unsubscribe from the EMC-PSTC list, click the following link:
https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1
<https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1>
--
Scott Aldous | Regulatory Compliance
Manager |[email protected] | 650-253-1994
------------------------------------------------------------------------
This message is from the IEEE Product Safety Engineering Society
emc-pstc discussion list. To post a message to the list, send your
e-mail to [email protected]
All emc-pstc postings are archived and searchable on the web at:
https://www.mail-archive.com/[email protected]/
<https://www.mail-archive.com/[email protected]/%20>
Website: https://ewh.ieee.org/soc/pses/
Instructions: https://ewh.ieee.org/soc/pses/list.html (including how
to unsubscribe) <https://ewh.ieee.org/soc/pses/list.html>
List rules:
https://pses.ieee.org/wp-content/uploads/2024/12/EM-PSTC-List-Rules.pdf
For help, send mail to the list administrators:
Mike Sherman at: [email protected]
Rick Linford at: [email protected]
For policy questions, send mail to:
Jim Bacher at: [email protected]
------------------------------------------------------------------------
To unsubscribe from the EMC-PSTC list, click the following link:
https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1
<https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1>
------------------------------------------------------------------------
This message is from the IEEE Product Safety Engineering Society
emc-pstc discussion list. To post a message to the list, send your
e-mail to [email protected]
All emc-pstc postings are archived and searchable on the web at:
https://www.mail-archive.com/[email protected]/
Website: https://ewh.ieee.org/soc/pses/
Instructions: https://ewh.ieee.org/soc/pses/list.html (including how
to unsubscribe) <https://ewh.ieee.org/soc/pses/list.html>
List rules:
https://pses.ieee.org/wp-content/uploads/2024/12/EM-PSTC-List-Rules.pdf
For help, send mail to the list administrators:
Mike Sherman at: [email protected]
Rick Linford at: [email protected]
For policy questions, send mail to:
Jim Bacher at: [email protected]
------------------------------------------------------------------------
To unsubscribe from the EMC-PSTC list, click the following link:
https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1
