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 > -- 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]/ Website: https://ewh.ieee.org/soc/pses/ Instructions: https://ewh.ieee.org/soc/pses/list.html (including how to unsubscribe) 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: <[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
