Silver electrical contacts are separated at constant speed and break arcs are generated in a DC100 V–450 V/10 A resistive circuit. The transverse magnetic field of a permanent magnet is applied to the break arcs. Dependences of the arc duration, arc dwell time and arc lengthening time on the strength of the magnetic field and supply voltage are investigated. The characteristics of the re-ignition of the break arc are also discussed. Following results are shown. The arc duration D is increased due to the increase of the arc lengthening time tm when the supply voltage E is increased for each magnetic flux density Bx, because the arc dwell time ts is almost constant. The arc duration D is increased due to the increase of both of the arc lengthening time tm and the arc dwell time ts when the magnetic flux density Bx is decreased. The arc lengthening time tended to become long when the re-ignition of the break arc is occurred. The lengthening time tends to become longer when the duration tm1 from the start of the arc lengthening to the start of the re-ignition is increased. Re-ignitions occurred frequently when the magnetic flux density of the transverse magnetic field is increased and the supply voltage is increased.

Silver electrical contacts are separated at a constant speed and break arcs are generated in a DC300V-450V/10A resistive circuit. The transverse magnetic field formed by a permanent magnet is applied to the break arcs. Alumina pipes are placed around the contacts to restrict the motion of break arcs. The dependences of the arc lengthening time and arc length just before arc extinction L on the strength of the magnetic field and supply voltage are investigated. It was found that the arc lengthening time increases with increasing supply voltage E and tends to decrease when the magnetic flux density Bx is increased. The arc length just before arc extinction L increases with increasing E and decreasing Bx. It also increases linearly with increasing arc lengthening time tm when no reignitions occur.