The Use Of A Hipot Tester

By Paul Olson


The abbreviation used in place of the word high potential is hipot. This term is used in reference to a given group of instruments used for testing electrical safety in electric products. Hipot tester is used to verify the electrical insulation in various wired assemblies including appliances and finished cables. Some of these wired assemblies are printed circuit boards, transformers, and electric motors.

In many cases, after the assembling/manufacturing of an appliance/product some current leakage of some level occurs. The interior of the product contains internal capacitance and voltages that often cause this minimal current leakage. It is normal for all devices to experience this leakage. However, in some scenarios, the current leakage may too high that it should be due to certain reasons.

Excess leakage may be caused by break down of insulation in the product, design flaws or many other causes. Such flaws usually lead to excessive current leaking and may cause electrical shock to anyone that comes in contact with the faulty product. The importance of a hipot test is to verify and ensure that the product is sufficiently insulated so as not to cause shock to the operator.

Dielectric Withstanding Voltage, DWV, is another term used in reference to the hipot test. At the time of the test, a high voltage is applied between the conductors that carry current in the product and its metallic shielding. Upon completion, there will exist a resultant current that makes its way through the insulator material. The term used for this current is leakage current and is tested using a high potential tester.

This process of testing has its basis on a major assumption. The assumption is that if the device works safely without its insulation breaking after being exposed to high voltage, then it can work fine under normal working conditions. During normal operation, the device should be able to withstand standard voltage application. This assumption is the source of the term Dielectric Withstanding Voltage.

The aim of the test is to stress the insulation used in the product. However, besides stressing the insulation, the test is also used to detect defects in workmanship. The most important aspects of workmanship that are monitored are the small gap spacings that occur between current-carrying conductors and earth ground. Under normal operating environment, these small gaps can be closed by contaminants, shock, vibration, humidity, and dirt.

When these small gaps close, the flow of current is enabled. This flow of current can be a major electrical hazard. Prior to product release into the market, it must be tested verify that such hazards cannot occur. The only applicable method that can be used in the detection of this type of defects is DWV. This is true in spite of there being other viable methods.

Manufacturers use high potential testers to do the verification of electrical insulation. Often, this simple electric device comprises of a switching matrix, current meter, and a source for the high voltage. All the points located on the cable are connected to the high-voltage source and the current meter through the matrix. Including a display and a microcontroller helps to automate the testing process.




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