Sunday, 9 September 2018

The Use Of A Hipot Tester

By Paul Olson


High potential is normally abbreviated as hipot. It is a term used in reference to a specific form of electrical safety testing apparatus, called a hipot tester. These apparatuses are used to verify electrical insulation of finished appliances, cables and other devices composed of wires. Transformers, printed circuit boards, and electric motors are among such devices.

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.

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 testing process makes one major assumption. The assumption is that if the insulation of the device is not broken by the deliberate application of excess voltage, then it should be safe for normal operation. The device should be able to withstand application of normal voltage, which is applied during normal use. The name Dielectric Withstanding Voltage comes from this assumption.

The objective during testing is to stress the insulation in the product. However, apart from inducing stress on insulation, the test detects any workmanship defects that may be present. The workmanship monitoring focuses on the tiny gap spaces occurring between the earth ground and conductors that carry current in the device. In normal working environment, these small gaps can be closed by dirt, humidity, vibration, shock, or contaminants.

The flow of current is allowed when the small gaps between earth ground and current-carrying conductors in electrical devices. This may cause a major electrical risk that must be rectified during manufacture before the product is made available on the market. Only DWV can be used for defect detection. Other methods may not be efficient like the DWV even though they can attempt to identify these defects.

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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