Simulation of Axial Magnetic Field in Vacuum Arc Interrupters at Intermediate Frequency

Characteristics of axial magnetic field (AMF) vacuum interrupters in intermediate-frequency (IF, 400-800Hz) power system of more electric aircraft is researched in this paper. The AMF distribution is solved by Maxwell. It can be concluded by the calculation as follows: In the process of current change, the axialmagnetic field changes slower in the central region than in other regions. The peak area of the magnetic field is located between the interlaced slots, and there is a significant residual magnetic field in the center area at current zero. When the frequency increases, the eddy effect is so serious that the magnetic flux density of the AMF decreases. For the center point, the residual magnetic field is stronger and the lag phase is bigger on account of the frequency increase, which will prevent the arc plasmas from diffusing. The eddy effect can be reduced by adding the number of slot in the contact blade. The maximum of the magnetic flux density is increased approximately linearly by adding the rotation angle of contact. The influence of magnetic field hysteresis on the breaking capacity of the vacuum interrupter is verified by experiments including arc appearance and arc voltage.