Magnetic Blowing of Break Arcs up to 360 VDC

Abstract

The phenomenon of magnetic blowing allows drastic reduction in arc duration. It is of specific interest in DC applications, more specifically in automotive applications. Blowing exploits the action of the magnetic force on the transitory arc formed during circuit opening. A new contact was described in a previous paper in which the magnetic field required for blowing is generated by the contact material itself. In the present study, aimed at a more thorough analysis of magnetic blowing, an external adjustable magnetic field (up to 320 mT) was produced by placing magnets on each side of the contact. The experiments were performed for voltage values from 42 V DC to 360 V DC and currents up to 100 A, using a resistive circuit. For considered magnetic field values, no magnetic blowing was observed below a certain critical current. At high current, the arc duration was found to be approximately current independent, following a phenomenological B 1variation. Under 42 V DC and the maximum current of 100 A, the arc duration under 320 mT was reduced by a factor of 100 as compared to the arc duration under zero field. Qualitative account of the present phenomena is obtained by considering that blowing is governed by the competition between the magnetic force acting on the arc and the force acting against arc motion, originating from the enthalpy expense needed to move the arc from a heated region at the contact surface to a colder one.

Relationships between Break Arc Behaviors of AgSnO₂ Contacts and Lorentz Force to be Applied by an External Magnetic Force in a DC Inductive Load Circuit Up to 20V-17A

“…In order to realize longer lifetime and/or better performances, reductions in break arc durations are strongly required. For such a purpose, increases in contact opening speeds as well as application of external magnetic field are often employed [1]- [7]. However, the authors' previous research results revealed that complicated phenomena can be observed and further research work is needed [8]- [14].…”