Contact Transients in Simple Electric Circuits

The proper functioning of electric contacts is of great importance. Much work has been done on contacts,^1,2 but comparatively little has been done on types of transient phenomena occurring at circuit break in inductive d-c circuits and their relation to contact erosion. Some work was done on transient types occurring at circuit break in telephone relay circuits by A. M. Curtis and his associates at the Bell Telephone Laboratories.³ This study dealt with transients in d-c circuits, including the fixed inductance of a relay winding and the small distributed capacity of a line wire, and embodied a study of the effect on the transient phenomena of changing the length of the line wire. The present investigation covered the variation of transients occurring for a fixed contact pair over a range of lumped inductance and lumped capacity values in a contact circuit; in addition, effects on the transients of varying the steady-state current (by steady-state current is meant the current immediately preceding circuit break), the voltage impressed on the circuit, and the circuit resistance were studied.