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
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