Slow Contact Opening Circuit Breakers

New results in this book show that at the point at which the arc root moves from the contact region, the driven flow could dominate the arc root commutation from the contact region. The arc root contact time analysis and modelling of the magnetic forces lead to able to estimate the minimum forces that moved the arc root from the contact region. The minimum force for the arc to move from the contact region, with contact opening velocities between 1 m/s and 10 m/s, was approximately 0.2 N.
The short circuit current showed a significant influence on the movement of the arc root and the magnetic forces on the contact area and the arc root contact time is decreased as the contact gap increases for contact velocities below 2.2 m/s. The contact opening velocity has a significant influence on the mobility of the arc root from the contact region. The arc root motion depended upon the quantity of the flow and area of the arc chamber venting.