AC vs DC Hi-Pot Test

[fifty60]

I have a requirement of do an A/C hi-pot test with a minimum of 500VA for a CE marking. We hired a compliance consultancy agency to do the first run of our equipment, and he advised us that we do not have to do the AC hi-pot test because our equipment has noise suppression devices and could be damaged from the AC hi pot test. He instead proceeded to do a DC hi pot test on our equipment.

We do have quincharcs across our solenoids and contactor coils, would this be what he meant by noise suppression? Does the compliance engineer's advice seem valid?

61010 (the IEC standard I am using) allows room to not do prescribed tests if you have a valid reason for not doing the test. For example, if you can show through manufactures information that the equipment would undoubtedly pass the test, then you do not have to perform the test.

Reasoning from this, since the AC test could damage the equipment then a DC hi pot test can be substituted. I am trying to figure out how to equate the 2 tests. For example, how can I say that a DC test performed for 1 minute an 2100V is equivalent to an 1 minute AC test of 1500V.

 

[Smart $]

...

Reasoning from this, since the AC test could damage the equipment then a DC hi pot test can be substituted. I am trying to figure out how to equate the 2 tests. For example, how can I say that a DC test performed for 1 minute an 2100V is equivalent to an 1 minute AC test of 1500V.

http://electrical-engineering-portal.com/what-is-hipot-testing-dielectric-strength-test

 

[fifty60]

Excellent link, thanks. My equipment under test has a control transformer. Would this be reason enough to not use an AC test? It would fry everything (SSR's, HMI, PLC, PID controllers) on the control circuit right?

Would this be reason enough to do the DC test? So that only the high side voltage cables are being tested, and not the 115VAC control circuit?

 

[Smart $]

Excellent link, thanks. My equipment under test has a control transformer. Would this be reason enough to not use an AC test? It would fry everything (SSR's, HMI, PLC, PID controllers) on the control circuit right?

Would this be reason enough to do the DC test? So that only the high side voltage cables are being tested, and not the 115VAC control circuit?

I don't know what would or wouldn't fry. I'm not aware of the devices mentioned having any particular withstand or leakage ratings. I've never heard of hi-pot testing such devices. The only thing I've ever been involved with is testing of conductors, and that has only been when they are isolated from any connection other than the test equipment. That said, I'm at a loss to provide any credible advice.

 

[fifty60]

I would have 500V across my control circuit for one minute during an AC test. I could disconnect the transformer, but the tests are to be done on the finished Equipment that is assembled for normal use...my point is, this would be a valid reason to do a DC test instead of an AC test...?

 

[Smart $]

I would have 500V across my control circuit for one minute during an AC test. I could disconnect the transformer, but the tests are to be done on the finished Equipment that is assembled for normal use...

Still can't advise being unfamiliar with the testing standard and its criteria.

 

[Smart $]

...my point is, this would be a valid reason to do a DC test instead of an AC test...?

If the purpose of the test to verify withstand and/or leakage levels without intentionally being destructive, I'd say yes... but JMO.

 

[don_resqcapt19]

I thought that a DC hi-pot test is considered to be a destructive test and is no longer recommended.

 

[ELA]

Have not done testing under that standard, but have under other equipment standards for CE and ETL precompliance testing.
We are allowed to remove MOV's during testing understanding that of course they would cause a fail as they are designed to suppress transients.

We did the DC test just because it allowed us to test for less time at an elevated voltage level for speed of production testing reasons.

 

[Smart $]

I thought that a DC hi-pot test is considered to be a destructive test and is no longer recommended.

I've heard the same...

 

[zog]

I thought that a DC hi-pot test is considered to be a destructive test and is no longer recommended.

Thats for MV cables

 

[Smart $]

Thats for MV cables

Oh! So destructive for MV cables but okay for LV equipment. What's wrong with that picture... :huh:

 

[zog]

Oh! So destructive for MV cables but okay for LV equipment. What's wrong with that picture... :huh:

Obviously the voltage level you test at would be different, the issue with cables is the propogation of water trees in extruded insulation used in MV cable insulation systems when tested with DC. This has been discussed here in detail many times, I don't want to get off topic.