Research and development of axial magnetic field electrode and its application

About 25 years ago, an axial magnetic field electrode was developed for vacuum circuit breakers. Since then, the electrode has been refined for practical application in vacuum circuit breaker interrupters through research achievements in vacuum arc and current interruption phenomena. Application successfully covers not only medium-voltage circuit breakers, but also high-voltage (84 kV), DC current and large-current circuit breakers. Recent advances in research on vacuum arc interruption phenomenon and vacuum arc control now makes improvement of current interruption ability possible. This paper reviews the basic phenomena of vacuum arc and current interruption in an axial magnetic field and also practical application of the axial magnetic field electrode based on 25 years' experience.