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.