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Friday, September 14, 2018

Uses 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.

Upon the manufacture or assembly of an appliance or product, it is usual for some degree of electrical leakage to occur. However, the leakage is usually very low and is brought about by internal capacitance and voltages inside the appliance. It is normal for such leakage to occur and it needs to be expected of every device. There exist a number of instances where the leakage, for some reason, may be excess.

Faults in the design or disintegration of product insulation among many other reasons may be the cause of the excessive leakage. These flaws often cause excessive leaking of current and may give rise to electrical shock for any individual that comes into contact with the defective appliance. The essence of a hipot test is to ensure and verify that the product has enough insulation so that the user of the device may not be electrocuted.

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.

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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