Page 10 - 2019 How-to-Specify E-Book
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 Pulsed-wave signals are known to generate discharges in connectors well below DC operating limits.1
5. The Effect of Air Pressure
The insulation properties of all gases, including air, are strongly influenced by their pressure. This pressure directly determines the density of the gas, and therefore the actual breakdown voltage. Connectors that use air as an insulator must be designed with this fact in mind. In addition, device engineers must apply correction factors to the normal voltage rating for any application in which a connector is expected to operate at non-standard atmospheric pressure.
The breakdown voltage of a connector in a gas will decrease as the pressure decreases. This phenomenon is called Paschen’s law, and the curves depicted in the following graph are of empirical origin.
A graphical representation of Paschen’s Law: an equation that defines breakdown voltage (i.e., the voltage necessary to start a discharge or electric arc between two electrodes) in a gas as a function of both pressure and gap length.2
Specialized high-voltage resources, like the Traité d’Électricité XXII, Haute Tension (i.e., The Electricity Treaty: High-Voltage) by Aguet and Ianovici of the Swiss Federal Institute of Technology, Lausanne, can provide more details and data for specific gases.
Connectors in Vacuum Applications
Paschen’s law is essential in vacuum applications. The graph provided here can assist in determining the correct parameters for a connector’s operation, but thorough testing is crucial.

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