Hi-pot test to 3 phase electric appliance

[jacklam2048]

Hi,

Can someone tell me if the Hi-pot test to a 3 phase 208VAC electric appliance is implemented as figure shown below ? i.e. with 1500VAC applied to L1, L2 and L3 of the electric appliance at the same time ?
Someone from the factory tell me that they apply 1500VAC to L1， L2 and L3 in turn (but not at the same time). Do you think the factory is wrong ?
Thanks a lot !

Jack

 

[Harald Kapp]

Look up the correct procedure in the applicable standard document.
Afaik testing each phase separately should be the correct way of testing. It givers a clear indication of each phase's insulation status.
Testing L1, L2 and L3 in a single test as shown in your image may be allowed or not, depending on what the standard says. If the test passes, the appliance will very likely pass the single phase test, too.
If the test fails, you will have to repeat the test per single phase to isolate the point of failure. It may so happen that the single phase test doesn't show a failure, however.
How? Imagine each phase being filtered by an EMC filter which usually contains capacitors from phase to ground. When testing a single phase, the AC current through the capacitor(s) connected to this phase may be low enough to not trigger the high pot tester. When all phases are paralleled, the combined current through the capacitors of all phases may exceed the threshold of the tester and the test may fail.
This may be a reason why the factory tests phase per phase although this takes more time and is thus more expensive.

 

[bertus]

Hello,

Perhaps the following pages will give you some info:
http://go.hipot.com/rs/414-IRJ-976/images/Ultimate-Guide-to-Electrical-Safety-Testing.pdf
https://electrical-engineering-portal.com/what-is-hipot-testing-dielectric-strength-test

Bertus

 

[Bluejets]

Any megger testing I've done is with a DC meter, not AC and normally one phase at a time to ground and phase to phase or neutral in cabling.
Usual range of meter output 500vdc for up to 440vac appliance and 1000vdc for up to 5000vac installation.
Great care and strict routine required for any high level testing as the tester can be lethal if handled incorrectly.

 

[jacklam2048]

Hello,

Perhaps the following pages will give you some info:
http://go.hipot.com/rs/414-IRJ-976/images/Ultimate-Guide-to-Electrical-Safety-Testing.pdf
https://electrical-engineering-portal.com/what-is-hipot-testing-dielectric-strength-test

Bertus

Thanks Bertus. Most of the information that I found on the internet are talking about Hi-pot test to single phase electric appliance and I am unable to find information about Hi-pot test to 3 phase electric appliance. That's why I post the thread.
But thanks for your information anyway !

 

[jacklam2048]

Look up the correct procedure in the applicable standard document.
Afaik testing each phase separately should be the correct way of testing. It givers a clear indication of each phase's insulation status.
Testing L1, L2 and L3 in a single test as shown in your image may be allowed or not, depending on what the standard says. If the test passes, the appliance will very likely pass the single phase test, too.
If the test fails, you will have to repeat the test per single phase to isolate the point of failure. It may so happen that the single phase test doesn't show a failure, however.
How? Imagine each phase being filtered by an EMC filter which usually contains capacitors from phase to ground. When testing a single phase, the AC current through the capacitor(s) connected to this phase may be low enough to not trigger the high pot tester. When all phases are paralleled, the combined current through the capacitors of all phases may exceed the threshold of the tester and the test may fail.
This may be a reason why the factory tests phase per phase although this takes more time and is thus more expensive.

Thanks Harald! Your reply is very useful to me !

 

[Martaine2005]

It looks like Bertus's cat is flirting with jacklam2048's cat. But jacklam2048's cat is having none of it...