A Development Of The Core Cup Longitudinal Magnetic Field Vacuum Interrupter

This paper has studied the structure of the one-sixth turn axial magnetic field of the cup vacuum interrupter with iron core and distribution of the axial magnetic field. The axial magnetic field reduces loss of radial energy of arc post plasma, and makes the arc voltage reduce. After the axial magnetism field of the vacuum interrupter is put into the iron core, the iron core makes the axial magnetic field distribute more uniform in the radial. The more uniform the axial magnetic field is distributed, the more uniform the vacuum arc is distributed on the surface of electrode. In the course of making, erosion on the surface of electrode is more uniform as well, so it is good for improving the breaking capacity of vacuum interrupt. In order to compare the influence between different shapes of iron core, two kinds of iron core of ring type and ring slotting type are designed in this paper.The finite element model is built for the axial magnetic field of the cup vacuum interrupter contacts without iron core and with two kinds of iron core. The calculation and analysis of the three-dimension axial magnetic field distribution characteristic on the axial magnetic field of cup the vacuum interrupter with iron core are carried out for the first time. The axial magnetic field distribution on center surface of contact gap and contact piece are calculated when the current is at peak. It can be found that the intensity of axial magnetic field and radial magnetic field uniformity are strengthened after the iron core is put into, this helps to improve the stability of the vacuum arc. The calculation to the eddy current on the contact surface and axial magnetic field of contact surface and center surface of contact gap are carried out while the current is at zero. After the iron core of ring type is put in, the eddy current on the contact surface will be increased, the axial magnetic field that the eddy current creates will be also increased. Average level of the eddy current will be decreased after the iron core is slotted, average value of the axial magnetic field will be decreased too. The hysteresis time of the axial magnetic field in the structure without iron core when the current is at zero is shortest. After the iron core is put into, the hysteresis time will be increased greatly, but if iron core is slotted, the hysteresis time will be decreased.