Tuesday 18 September 2018

The Use Of A Hipot Tester

By Paul Olson


The term hipot is usually used as an abbreviation for high potential. It is a term that is used to refer to a certain class of electrical safety testing instruments referred to as a hipot tester. These instruments are used in the verification of the electrical insulation in finished cables, appliances, and other wired assemblies. Such assemblies include electric motors, transformers, and printed circuit boards just to mention a few.

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 place of the term hipot test. This process involves application of a high voltage between the earth ground shielding and the conductor in the product that carry current. Exposure to excessive voltage causes resultant current flow through the product. A high potential tester is the gadget used in monitoring of this resultant current, which is also called leakage current.

One major assumption is made in hipot testing. The assumption is that by applying excessive voltage, the insulation of the product should break, and if it does not, then the device should work fine under normal conditions. The appliance is supposed to be resilient against normal voltage, which is often applied in ordinary everyday use of most devices. It is this assumption that gives rise to the name Dielectric Withstanding Voltage.

The test is aimed at stressing the insulator used in the appliance. Apart from stressing the insulator material, however, the test is additionally used to identify workmanship flaws in the product. The most critical monitored workmanship elements are minute spaces existing between the earth ground and current-carrying conductors. In ordinary environment of operation, shock, humidity, contaminants, shock, and dirt may fill these spaces.

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.

An electric device that manufacturers use in verification of electrical insulation is a high potential tester. It is made of a source of high voltage, a switching matrix and a current meter. Connection of the source of voltage and the current meter is done by the matrix switch. Including a display and a microcontroller automates the process of testing.




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