Hipot Tester Insulation Testing

A hipot (short for high potential) test determines the ability of electrical insulation to withstand normally occurring over-voltage transients. The hipot tester applies high voltage to the insulation barrier of the DUT and verifies there is no breakdown. It is a simple pass/fail test performed as a type test on a representative sample unit or as a routine production test. Maximum allowed leakage is usually in the range of 0.1 to 5mA, or as specified in the test standard. The actual leakage value for each DUT may be recorded for quality assurance.

Many standards (such as IEC 60950) specify an ac test voltage that is twice the operating voltage plus 1000V. Most allow the use of either ac or dc voltage. The test setup and procedures are identical for ac and dc, although the dc level should be equal to the ac voltage peak. The test time is normally 1 minute, but in some situations, such as high volume production testing, a shorter test time may be permitted at a higher voltage.

Hipot tester

Typically, a hipot test is performed on the mains wiring of electrical equipment. One lead of the tester is connected to safety ground (earth ground). The other lead is connected to the line and neutral power leads. Often the hipot tester has a built-in ac receptacle to make these connections (as shown in the photo).

If the circuit under test has a power line filter, hipot tester may indicate a failure due to current flow to earth thru the Y capacitors. The safety standard usually allows the user to disconnect these capacitors prior to testing or increase the upper current limit to compensate for the additional leakage. Alternatively, a dc test voltage can be used. Most hipot testers also include a low limit to ensure the test fails if the DUT is not connected or the test is interrupted. Unlike megohmmeters, which are usually battery-powered, almost all hipot testers require ac power.

In summary, insulation resistance is typically a field measurement to assess insulation quality. Hipot testing is usually a safety check performed in the factory to verify the product design and manufacturing process. This difference determines whether a megohmmeter or hipot tester is the appropriate insulation testing instrument.

Leave a Comment

Your email address will not be published. Required fields are marked *