Hipot testing

[rgalvez]

We want to use hipot test in slip rings (24 rings) and we've made an automatic tester which uses switching matrix and a hipot tester.

We would like to know if anyone of you knows or is aware of the minimum dwell time for applying 250 V on this test? The matrix switches the tester to do the hipot between one circuit (ring-cable) and the rest, then another circuit and the rest, and so on.

Thanks.

RGB.

 

[Foxfur]

I'd think that 10 seconds would be a good place to start. Or you could do a destructive test on a unit or two just to establish the upper threshold. If this item is going to be marketed, a beefier unit that can stand up to relatively long hipot tests would stand out as a robust device. Longer is better if you expect the unit to encounter error states, especially if the possibility exists for a user to install the unit incorrectly, thus subjecting it to stresses that might destroy it. If you can document that it can stand up to dummies and clods, you can resonably state that it is "Idiot Proof" or perhaps a friendlier term that conveys the same message.
Perhaps UL could offer you some guidance as well.
Best wishes,
Foxfur

 

[dwayned]

A hipot test is a very common product safety test which is done as a type test as well as a routine production line test. The Type test is one that a product safety testing lab would perform on a product when it is submitted for a safety agency listing. The test time for performing a type test on a product is usually 60 seconds while a routine production line test is reduced to a 1 second test. The test voltage is also different for these test the routine production line test is normally performed at a test voltage that is 20% higher than the type test. Are you testing to any product safety standards or is this an in house specification?
A good web-site that had a lot of technical articles on product safety testing is

http://www.asresearch.com.

Good Luck
dwayned (electrical)

 

[rgalvez]

Thanks a lot "Foxfur" and "dwayned" for your answers.

In fact, the electrical tester we use is from AS Research and the test runs under a production basis which is a strong factor for the timing of the test as a normal one consists of continuity, hipot and insulation resistance and it takes about 130 seconds per piece from the time the operator takes the piece to test until he releases it.

All this becomes an issue engineering-vs-production because as engineers time up the tester, off course, less pieces can be tested in an hour. That's why we're looking for a point were we won't sacrifice the pieces with a strong test and test as many pieces as we can per hour.

Thanks again.

RGB.

 

[uppili11]

130 secs is too long a period for such tests.ideally for 500v ac hipot test we apply for 3 secs with a leakage current limitation of 3 mamps.In case you would like to reduce the time and still find out any fault reduce the leakage current as well as timimg.

 

[HVoltage]

The PI (Polarization Index) of the insulating materiel should be known to determine the dwell time. You see the PI will determine the amout energy and time to achieve maximum polarization this energy can be seen by the Hi-pot as leakage current. For a true leakage current reading it must be taken after this polarization shift. At the 250 volt test this shift will be small but should be determined for the shortest possible dwell time.