What is a withstanding voltage test?


The withstanding voltage test verifies whether an electrical product or component has sufficient dielectric strength (determine a dielectric breakdown). All electrical appliances must be safe for use. Under no circumstances should they put users’ lives at risk nor damage their properties. Users must be protected against electric shock, injury, fire, explosion, and other potential hazards. Protection against electric shock and fire is especially vital, also the safety for non-technical users is particularly important.

Electrical components can be roughly classified into two types: components that allow electricity (conductors) and prevent it (insulators). The internal defects of insulators may lead to electric shock or fire hazards. To prevent such electrical accidents, the following tests should be conducted: a withstanding voltage test, insulation resistance test and leakage current test, which are conducted between the primary circuit and the exposed conductive part (e.g. chassis) and an earth continuity test for a three-phase AC input device. The international safety standards require that manufacturers of electrical products conduct the withstanding voltage test at least and one to three of the other tests in combination. A number of international safety standards make it mandatory to perform the withstanding voltage test not only during the type inspection to verify the safety of the product design but also during the 100 percent inspection in the final process to verify all finished product safety.

Therefore, the withstanding voltage test is the fundamental test for ensuring the safety of an electrical product.

As the withstanding voltage test is also referred to as a dielectric strength test, the purpose of this test is to verify whether an electrical product or part has sufficient dielectric strength to withstand the voltage. In other words, the test is intended to detect an insulator defect.
The test method is to apply an high AC or DC voltage to an insulating product, typically 10 to 20 times greater than the voltage normally applied on a circuit of a DUT, for a specified duration of time.
If no dielectric breakdown (no sudden increase in current inconsistent with Ohm’s law) occurs, that the insulating product is judged to have sufficient dielectric strength.

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