What is Hipot Testing?

A hipot test — also known as a dielectric withstand test — measures the level of electric insulation in a device by ensuring that current will not flow between two specified points under high voltages. Among other problem areas, hipot tests help manufacturers identify:

• Damaged insulation
• Corrosion
• Improperly spaced terminals
• Stray wires
• Manufacturing defects

As a non-destructive test, a hipot test connects one side of the supply to the conductor and grounds the other side. When high voltage passes to an adequately insulated conductor, the insulation won’t break down. In some situations, an acceptable minimal flow of current may be allowed, though the amperage of the current must remain within acceptable safety guidelines.

Hipot tests typically apply twice the projected operating voltage and an additional 1,000 volts to the conductor for 1-2 seconds to determine if the insulation can handle excess transient voltages. Hipot tests offer compatibility with alternating current (AC) or direct current (DC), depending on the type of voltage the device uses for power. The safety agency that regulates the device under test (DUT) may provide additional hipot testing guidelines.

AC test voltage stresses the insulation when voltage is at its peak, whether positive or negative. Conversely, the DC hipot test can only test in a single polarity. With AC tests, testers will apply maximum current all at once, whereas a DC test requires a more gradual application.

DC tests can test products with lower insulation levels more effectively by setting lower trip levels.

DC tests also can identify potential insulation failures before they occur, allowing manufacturers to salvage the DUT.

DC tests can also more easily identify low dielectric resistance areas and mechanical damage that may affect the insulation.