Safety testers (also named hi-pot tester/hipot tester/hipot test) are designed to ensure safe operation of DUTs under various operating conditions and environment.
Dielectric withstanding test was the original official name, and it is commonly known as High Potential and it has evolved into Hipot for short in the industry today.
Safety testers have a very extensive coverage, and Hipot is only closely related to electrical safety tests, which require many international safety regulations such as CE, UL, VDE, etc.
GW Instek provides four products:
Why is hipot testing important?
Withstanding voltage, insulation and grounding resistance (Ground Bond) are the test functions of the electric safety tester. Among them, the withstanding voltage test is a required test item for electrical equipment before leaving the factory.
What is the common test voltage for hipot test?
There are three common test voltages for the withstanding testing: AC, DC, and Impulse.
The AC voltage test:
The AC voltage test is most accepted by standard units, because the AC voltage is the same as our actual electricity environment. Both positive and negative half cycles are tested. For the stray capacitance of the DUT, the AC voltage test does not have the issue of charging and discharging.
The DC voltage test:
It is necessary to establish sufficient test voltage on the insulation resistance, and the current required for testing with a DC waveform is smaller, which is relatively safe compared to AC.
The Impulse voltage test:
Impulse is mainly focused on testing circuits or components for transient overvoltage limiting devices by simulating the actual appearance on transmission and distribution lines. Transient voltage is divided into pulse and oscillation. Impulse simulates pulse transient voltage such as lightning strike as well as devices used in substation and transmission and distribution systems, such as circuit breakers, isolators, voltage isolators which require to be tested with this applied voltage.
In sum, the test voltage is to restore the appearance of the actual use environment or solve the test issues.
How to choose the output capacity of the withstanding voltage tester?
The output capacity of the withstanding voltage tester is in VA, which refers to the product of the maximum rated AC test voltage and the maximum rated current. At present, 100VA/200VA/250VA/500VA withstanding voltage testers are available on the market. Taking AC 5000V as an example, 500VA can provide 100mA, and 200VA can provide 40mA. The output capacity actually depends on how much current is required to maintain the test voltage. We expect to establish enough test voltage on the insulation resistance to be tested to confirm whether the insulation is good. When the insulation breaks down, the insulation resistance will reduce. If the current at this time is insufficient (insufficient capacity), it cannot establish a sufficient voltage in this resistance with a decreasing value.
This phenomenon is similar to the DC power supply switching from CV mode to CC mode. When the insulation resistance is very large (the load current is small), and when the insulation breaks down, the insulation resistance becomes smaller (the load current becomes large), and the capacity is needed to support it. Therefore, the destructive experiment of materials in the R&D unit or the laboratory of the third-party manufacturer will require a capacity of 500VA. The routine test of the production test commonly utilizes 100VA model. The reason is that the yield rate of the product is very high during mass production. Taking the insulation resistance of 100MΩ as an example, to establish a test voltage of 5000V, the load current is only 50μA and to establish a test voltage of 1500V, the load current is only 15μA, which is more than enough for the capacity of 100VA. Of course, if it is AC withstanding voltage, the influence of equivalent capacitance must be considered.
Why GW Instek is your best choice?
We can help you safely complete the tests when analyzing insulation materials or conducting production testing. For more information, please visit white paper” Is Your Hipot Tester Safe? Ten Whys of Electric Safety Testing” .
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