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5 Things to Know Before Buying 120KV DC hipot tester

Dec. 09, 2024

Should I HIPOT before or after other tests? [Archive]

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DJ-Jokes

My electrical knowledge is limited, but I'm responsible for reviewing some testing practices for our company and trying to standardize them. We have a few product lines that we conduct our functional testing cycle followed by a HiPOT test, and a few other product lines where we HiPOT test it first and then do our functional testing.

I'm trying to understand if there is a standard practice of running the insulation testing after or before other tests due to the possibility of one set of tests affecting the other set of tests. These are all AC units and we are conducting an AC HiPOT test.

Any help in understanding what the best practices would be is appreciated.

Cheers.

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It has now been about 3 months I don't seem to be getting the type of advice that I am looking for, so let me start again.

I have units that in the field will have operating conditions of:
Either 120V or 240V AC
less than 2A draw
Think of it as a speed controlled window fan for all intensive purposes.

Some of the common components used are:
120V or 240V C frame 1.2A motors
SPT-2 and SPT-3 wire (aka "lampcord")
UL XLPE 18g wire
Various 18g insulated connectors
Various mechanical switches
Various rheostats

I have two options for testing to try to standardize and do not understand the implications of running each test sequence.

Option A:
Apply either 120V or 240V power as appropriate to check all switch routings and "run" functionality (5 to 30 second run time).
Apply an AC HiPOT test to confirm insulation does not "leak".
Concern: In this scenerio it appears that the HiPOT test could (in very rare cases) burn out the unit and by not running the functional test first could cause a dead unit to get to our customers.

Option B:
Apply an AC HiPOT test to confirm insulation does not "leak".
Apply either 120V or 240V power as appropriate to check all switch routings and "run" functionality (5 to 30 second run time).
Concern: In this scenerio it appears that the application of power could cause a situation where the HiPOT test would fail if rerun. My opinion of this is primarially due to the run time of the motor and the switching process.

I am trying to understand:
Which (A or B) has the least risk of a failure getting past the testing.
If there is a "standard" method for order of test application based on the stresses / failures that could be missed after each test.

Cheers.

madMAX

DJ-Jokes

Generally speaking its better to do the DC insulation test first (insulation resistance) because its done at a much lower voltage. Any insulation problems would show up in this test. Do the AC withstand test only if insulation resistance values are acceptable.

Thanks madMAX. I'm not familiar with that type of test as it is not something we currently do. To be a bit more explicit, we are making wiring harnesses that can contain some of switching devices attached to a small C frame motor. The HiPOT test is conducted because of customer / industry requirements. I realize that the HiPOT test does by its nature cause the insulation to be stressed and that repeated testing is not desired.

That is part of the reason for my question. It seems to me that conducting the HiPOT prior to any functional testing may cause an unexpected safety issue, but running it after the functional test may cause the unit to be DOA.

So is your recommendation that we insert an insulation resistance test first, followed by a HiPOT and then end with a functional test?

benlanz

It depends what you are testing. Are you testing MV or HV solid dielectric cable by chance?

DJ-Jokes

No, consider it to be similar to an oscillating floor fan or a lamp or whatever. It is just a consumer electrical product running at either 120 or 240V. I've revised the original thread description to give more details of the components involved.

madMAX

Given the new details, a simple V megger test would be sufficient. The insulation of that wire is most likely rated 600V (look at the markings on the wire) a hipot would compromise the insulation. Measure each wire to ground and each wire to each other for 1 minute. You are looking for 100 Megohms but its not unheard of to turn something on with 1 Megohm. You might find this article helpful: http://testguy.net/content/195-Basic-Test-Equipment-Introduction-Insulation-Resistance-Tester

codycody103

Qustion is already answered but i agree, normally do meggering first to ensure cable stability

Contact us to discuss your requirements of 120KV DC hipot tester. Our experienced sales team can help you identify the options that best suit your needs.

Achandler

I would not hipot anything rated 240v. A v megger is sufficient. What voltage are you using to hipot test?

bbryant

copes

It would be interesting to know what you consider as a hipot test. Because given the information, as stated above you should only test with a dc megger to the values pointed out in table 100.1 of NETA ;), depending on the rating of this wiring.

gchoquette

I'm trying to understand if there is a standard practice of running the insulation testing after or before other tests due to the possibility of one set of tests affecting the other set of tests. These are all AC units and we are conducting an AC HiPOT test.

Cheers.

The above answers look perfectly fine (V DC Insulation tester)

However, it appears that you are doing a repetitive production of some electrical cooling system. If this is to be sold in the consumer or industrial marketplace, you may need to do an electrical compliance check of some sort, with calibrated instruments.

There are instruments that specifically do compliance testing. They are intended for production manufacturing, which I assume is what you are doing.

They can also be rented, if you just doing a single temporary run of the product.

Here's one brand of those instruments:
https://www.arisafety.com/
They have both calibrated HiPots and Ground Bond testers. You can also automate the tests if you have a lot to do.
https://www.arisafety.com/products/hipot-tester-hypot/
https://www.arisafety.com/products/ground-bond-tester-hyamp/

Another, more expensive brand is Haefley.

I am not associated with either of these companies. Just letting you know what manufacturers use for this type of work.

NBatson

DC insulation resistance often called megging. run it at 500VDC and you should be good you can run it at VDC but I would start low and go up. A 1 minute test is kind of the standard for testing insulation. Megger has a great write up on insulation resistance if you want to take your knowledge a little further. Its short and written in plain English. Google "Megger A stitch in time," it should have a downloadable pdf of the write up.

Sir_Stig

The above answers look perfectly fine (V DC Insulation tester)

However, it appears that you are doing a repetitive production of some electrical cooling system. If this is to be sold in the consumer or industrial marketplace, you may need to do an electrical compliance check of some sort, with calibrated instruments.

There are instruments that specifically do compliance testing. They are intended for production manufacturing, which I assume is what you are doing.

They can also be rented, if you just doing a single temporary run of the product.

Here's one brand of those instruments:
https://www.arisafety.com/
They have both calibrated HiPots and Ground Bond testers. You can also automate the tests if you have a lot to do.
https://www.arisafety.com/products/hipot-tester-hypot/
https://www.arisafety.com/products/ground-bond-tester-hyamp/

Another, more expensive brand is Haefley.

I am not associated with either of these companies. Just letting you know what manufacturers use for this type of work.

This is closer to what OP needs, but for the people saying to only megger it, factory acceptance testing of CSA/cUL/UL devices have corresponding standards that require specific test levels of the devices and cables. Not sure on the UL levels, but the CSA requirements are 1.5kV AC for 60 seconds on control components (there are reductions for certain devices, and a 1 second test voltage that is higher). Switchgear has a different table, but with similar requirements of 60Hz for 60 seconds. An insulation resistance tester is useful in most cases to do before a hipot, at least on >600V gear were the voltage applied is drastically different, but not required.

I believe the OP is wondering whether they should hipot first, then function test, or function test then hipot. Really there are pros and cons of each, but basically if you only have a hipot and a power source (and I'm assuming a multimeter) I would personally do a shorts and grounds check with the meter (and a visual on the wiring if it's at all possible at that stage), do the hipot, repeat the S&G check and then function check it. If it's as simple as a occilating fan, then the hipot should catch any insulation issues to ground, and the S&G should catch any obvious phase to phase shorts, at which point as long as you have a standardized energization procedure the insulation should not be negatively effected in a way that the hipot might catch.

If you do the hipot last, you risk sending out equipment that might have fuses or other components that might have been damages from the hipot test and would not be caught by the hipot test itself. In a perfect world you do a function test, then hipot, then a more basic function test that verifies nothing was damaged by the hipot, but that's not always possible.