I always feel blessed when PSES Hall of Famers provide their insight! Thank you kindly, gentlemen…
Hazard-based approach is where I’m heading. Although this machine will not touch the ground directly, I have no confidence the trailer tires will provide any sort of consistent isolation: the machine uses water as part of its work process, the surrounding ground may be wet as well. Having said that, I’m almost ashamed to have asked if hipot is necessary—IR testing doesn’t replace hipot, it is a lower stress complement to it. Now, a real concern is stray leakages during the hipot testing. The test environment will be as secure and dry as possible. However, the machine itself may have trace moisture on parts of the structure, making testing a challenge. All will be documented in risk assessment & test plan. Have a great weekend, Chet Summers From: Ralph McDiarmid <[email protected]> Sent: Friday, February 27, 2026 4:50 PM To: [email protected] Subject: Re: [PSES] hipot considerations for large electric machinery? Think Before You Click: This email originated outside our organization. I like the hazard-based approach idea. It may simplify the test plan as well. From: John Woodgate <[email protected]<mailto:[email protected]>> Sent: February 27, 2026 1:01 PM To: [email protected]<mailto:[email protected]> Subject: Re: [PSES] hipot considerations for large electric machinery? Wow, monster! The number one question is: Is it used on the trailer, where it's insulated from the planet by the tyres, or tires, or is it only used when off the trailer and in contact with the planet? On the trailer, I don't see a compelling need for hi-pot for safety reasons, but it would be good for reliability. Off the trailer, if there are any exposed conductive parts that are not bonded to ground, hi-pot is essential. In cases like this, it's good to adopt the 'hazard-based' approach. Set aside the standards and regulations, consider everything that could go wrong, how likely each is and what would be the worst outcome. Fix the high-probability cases and the lethal cases and you probably surpass all the standards and regulations. On 2026-02-27 20:26, Chester Summers wrote: Hello, colleagues— I’m looking at hipot testing a physically large electric machine and trying to determine the best approach to complete the task. NFPA 79 & C22.2 No. 301 say hipot is required, IEC 60204-1 leaves it to the manufacturer’s consideration. The machine supports outdoor construction work, contains several 3-phase 480V motors and is powered by on-board genset, all mounted on semi truck trailer. Process control is done through simple pushbutton switchgear panels. There are no programmed electronics or PCBs. This is by far the largest product I’ve considered for hipot. Isolation of the product isn’t feasible (won’t fit on test table :) and disassembly is strictly limited. I’m looking for practical guidance from those that routinely test and inspect physically large equipment. IR and ground bond testing are already planned. Risk assessment thus far tells me hipot may not be essential, however, the standards say… How should I address this elephant? Thanks in advance & best regards, Chet Summers ________________________________ This electronic message including any attachments ("Message") may contain information that is privileged, confidential and/or exempt from disclosure under trade secret and other applicable law. If you are not the intended recipient, notify the sender immediately, permanently delete all copies of this Message, and be aware that examination, use, dissemination, duplication or disclosure of this Message is strictly prohibited. This email and any files transmitted with it from Charles Machine Works are confidential and intended solely for the use of the individual or entity to which they are addressed. ________________________________ 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]<mailto:[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]<mailto:[email protected]> Rick Linford at: [email protected]<mailto:[email protected]> For policy questions, send mail to: Jim Bacher at: [email protected]<mailto:[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 -- Best wishes John Woodgate RAYLEIGH Essex OOO-Own Opinions Only www.woodjohn.uk<http://www.woodjohn.uk> If something is true: * as far as we know - it's science *for certain - it's mathematics *unquestionably - it's religion [https://s-install.avcdn.net/ipm/preview/icons/icon-envelope-tick-green-avg-v1.png]<http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient> Virus-free.www.avg.com<http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient> ________________________________ This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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To post a message to the list, send your e-mail to [email protected]<mailto:[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]<mailto:[email protected]> Rick Linford at: [email protected]<mailto:[email protected]> For policy questions, send mail to: Jim Bacher at: [email protected]<mailto:[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 This email and any files transmitted with it from Charles Machine Works are confidential and intended solely for the use of the individual or entity to which they are addressed. - ---------------------------------------------------------------- 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
