The Effect of Magnetic Forces on Arc Control

 The Effect of Magnetic Forces on arc control

The magnetic forces on the arc root
increase as the arc current increases. The contact gap has a minimal influence on the
magnetic forces on the arc root. The magnetic forces on the arc root are mainly
dependent on arc current.

The different is the influence of the shapes of the
contacts are modelled. From the experimental results in Section 4.3.1, Chapter 4, the
Ag/C on the moving contact causes a longer delay in the tip of the moving contact.
An Ag/C step and Ag/C flat on the fixed contact are used to compute the magnetic
forces on the arc root, see Figure 3.19, Chapter 3.

The material of the arc runner is Cu and it is 1.0 mm thick. The material of the
contact is Ag/C (95/5 %) and 0.8 mm thick. The anode is on the moving contact and
the cathode is on the fixed contact.
A Silver/Graphite contact pad with a step to the surface of the arc runner is shown in
Figure 5.4. A Silver/Graphite contact pad flushes without a step to the surface of the
arc runner is shown in Figure 5.5.

Reference: Arc Control in Circuit Breakers: Low Contact Velocity Paperback – January 1, 2017 by Dr Kesorn Pechrach PhD (Author)