Electric Strength

The electric strength of a unit under test (UUT) is tested with the HV-AC test (a high voltage test with alternating current). It must be distinguished from the insulation resistance.

 

The electric strength of a UUT is the capacity to avoid a dielectric breakdown or an arc between two points up to a certain voltage.

 

An arc is a short-term, electrically conductive connection between two points, which are actually insulated from each other through the surrounding medium (e.g. air). It is a sudden short circuit, carrying a very high current.

 

Though the insulation resistance of a UUT can be very high, the electric strength is often limited. It mostly depends on the geometric characteristics inside the UUT. Two side-by-side circuit paths on a back plane even with enough distance and an insulation resistance that isn't measurable anymore can have a relatively low electric strength in case prominent tips occur through soldered components or plugs.

 

To reduce the risk for an arc by excluding a direct short circuit a short test (a low voltage test) is usually processed before a HV-AC test will be started.

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Insulation Test