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Axial magnetic field (AMF) contacts are applied in vacuum circuit breakers to interrupt high short-circuit currents. A magnetic field parallel to the current flow in the arc column improves the breaking capacity by affecting the arc mode. Depending on the design of the contacts, this magnetic field can take different directions over the contact surface. In this paper, measurements of bipolar and quadrupolar AMF contact systems are presented. For bipolar arrangements, the polarity of the field changes once and for quadrupolar arrangements twice. Due to different eddy current paths, the residual magnetic field at current zero is significantly higher for the quadrupolar arrangement. The breaking capability of two contact systems was investigated and completed by measuring the post arc current.
Date of Publication: Oct. 2003