Electrodynamic Repulsion Between Electric Contacts With Arbitrary Current-Density Distribution

If the closed contact of an electric switching device is subjected to a high-current impulse, electrodynamic forces may open the contact, and the occurring arc may damage the device. The effect can be described by Holm´s well-known approximate formula. Unfortunately, it contains a parameter which, in most cases, cannot be determined with the necessary accuracy: the radius of the contact spot. Therefore, several experimental studies on this problem have been performed. Nevertheless, in the case of axisymmetric contacts the repulsive force is shown to be computable with full exactness from any given current-density distribulion at the contact spot. The discussion of this result may help to answer the question of whether or not the repulsive force can be reduced by changing the current distribution Within the contact members (e.g., changing contact geometry or material).