Characteristics of a Mechanical Circuit Breaker with New Induction Needle and Magnets Type to Extinguish a DC Arc

Abstract

Permanent magnets are currently attracting much attention as they are used in various application devices requiring high magnetic force. There are many types of permanent magnets with different properties, and they need to be tested for suitability for the applied devices. Sintered NdFeB permanent magnets have a large coercive force and are used in a variety of application systems. In particular, they are being used in circuit breakers to protect the DC transmission and distribution systems, which are actively being developed now. DC maintains a constant current value because it does not have a frequency. Thus, it is very difficult to interrupt large transient currents when an accident occurs. Therefore, a new type of induction needle and a permanent magnet near a mechanical break contact were combined. This induction needle is serially connected to a ground wire. This new breaking technique extinguishes the arch that occurs between the contacts by pushing it to the ground using an induction needle. The permanent magnet applied here, however, must be strong against a high-temperature arc that occurs quickly, and must generate a high magnetic force. Simulations were conducted with FEM (finite element method) and TDM (time difference method) using Maxwell, an electronic analysis program, and a permanent magnet that is appropriate for use as a component of a circuit breaker was selected. Consequently, it was found that the use conditions of permanent magnets varied by the arch generated in the mechanical circuit breaker.