Electrical equipment and appliance manufacturers use a variety of different Safety Testers in design, testing, and certification to meet OSHA, UL, CSA, ETL, CE, and other international standards in order to reach domestic and global markets. Repair, facilities, and contractor personnel also use Safety Testers.
We at TEquipment get a lot of calls for electrical safety testing where there is a UL or other requirement that there needs to be a hipot test or a ground bound test.
We are here to help! Please call us with any questions.
Hipot Testers (High Voltage Testers aka Dielectric Tester)
Hipot Testers, also known as High Voltage Testers, Dielectric Testers, Dielectric Withstand or Breakdown Test, are high voltage with low current safety testing instruments for testing insulation in finished electrical equipment and cables. They test whether insulation is performing its duty of keeping stray electricity from escaping and shocking a person. It is a required test for industrial and consumer appliances and electrical products and very commonly found on a production line.
Types of Hipot Testers
Typically this test applies a voltage from 500V to 5,000V. Some units go up to 50kV or higher depending on the application need but the majority of tests are usually 5KV and below. This test applies a high voltage beyond what the product would normally experience in use but not so much that the unit should fail. A passing unit would not have a break in the insulation resulting for a large voltage.
AC Hipot Test
DC Hipot Test
When selecting a Hipot tester you need to know the max voltage you need to test at the max current. Smaller units have a 20Ma trip current while others have a 100 mA or great trip current. Some units that are special order can be made to fit the exact requirements of your test.
Comparing DC Hipot vs AC Hipot (While AC Hipots may be more popular, when is a DC Hipot needed?)
DC Hipot Test Advantages
DC Hipot testing is effective regardless of the input capacitance.
In highly capacitive circuits, DC testing will charge the capacitor where it might trip with an AC tester and not be possible to test at all.
"Y" capacitors are frequently used by instrument/appliance manufactures to protect DC electronics like controls and computers against high frequency surges and RF noise in the AC line by shunting noise to ground. An AC Hipot will charge in positive then to zero and then negative will have a harder time with Y capacitors, than a DC Hipot for this application
DC Hipot Test Disadvantages
The current trip for the leakage may be set on a significantly lower value. The manufacturer may then identify and remove products with marginal insulation that may have passed otherwise.
AC Hipot Test Advantages
Only one direction of polarity can be tested with DC
Not all test standards consider DC testing to be on the same par as AC testing. While most standards allow either, testing of large motors is still by AC hipots and there are some very old legacy standards that predate the availability of DC hipots
Unlike its AC counterpart, the DC hipot test cannot replace the test for line voltage leakage
AC Hipot Test Disadvantages
AC testing checks both polarities of voltage. Products that use AC for normal operation cannot be tested by DC voltage
There is no waiting needed following an AC voltage test. DC Hipot testers make DC with a capacitor, so there are a few seconds at the end of test to discharge the internal capacitor. Might be an issue in a production line where speed of testing is important
AC testing is accepted by all test standards
Download a detailed white paper on AC Hipots from Phenix Technologies: Phenix AC Dielectric Paper
May trip or not be possible to test at all highly capacitive circuits (see first bullet for DC Hipot Advantages)
It requires more current during testing and may actually weaken the insulation. This in turn may cause failure of the product in normal use. We do not have hard data on this and welcome comments
Insulation Resistance Test (High Resistance Test aka IR Tester, Megaohm Meter, Megger)
Note an IR Tester is NOT a substitute for a Hipot Tester
This is a high resistance test to see if the insulation has a breakdown. It detects deterioration of insulation. The typical test applies a voltage between 500V and 1000V (some IR testers go up to 10kV but most applications for hipot testers with built in IR testing only need 1kV). A IR tester measures the total resistance of the insulation. It does this by applying a voltage with a very small current. The ranges of resistance for a passing value can be from a few megohms to teraohms. Often this test is done to provide maintenance for predictive failure of a unit.
If your application is not for a HiPot and instead for an IR Tester, please see our full IR department page:
Products > Micro-Ohmmeter / Milliohmmeter / Megohmmeter > Megohmmeter / Insulation Resistance Testers
Ground Bond Test or Earth Bond Test (High Current Test)
Ground Bond Testers measure the resistance between ground and the body being tested. The values for passing this test depend on the standard but usually .5 ohms or sometimes 0.1 ohms meet specified standards.
Please check your requirements. This test uses a high current 20-62 Amps. The test is to insure the item in test does not produce a shock if the unit was to fail in a high current situation. High current could happen if the unit was to get a surge or experienced a malfunction. This could happen before a circuit breaker was able to trip.
Leakage Current Tester
One of the biggest applications for a Leakage Current Tester is in the medical industry, where several standards require a leakage current test. A current leakage tester looks for current that flows across the insulation. The test is usually used to test at a voltage above the input voltages of the unit in test. Standards dectate how much current is acceptable. Usually results that are passable are in the microAmp range.
Key in selection is knowing which specific standard needs to be met
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