As the core component of vacuum interrupter, the contact's arc extinguishing ability will directly affect the DC breaking process. The existing contact models usually rely on transverse magnetic field or axial magnetic field to regulate the vacuum arc and help the vacuum circuit breaker to break. In this paper, a type of contact which can generate both transverse magnetic field and axial magnetic field is designed. The main design idea of the contact is that the vacuum arc generated on the surface of the transverse magnetic contact rotates and diffuses into the axial magnetic field under the action of electromagnetic force, and the arc changes from the concentrated state to the diffused state under the action of the axial magnetic field. The vacuum arc in the diffused state can greatly reduce the ablation on the contact surface and improve the service life of the contact. Firstly, three contact models are established by finite element simulation software, and the magnetic field distribution generated by the contact under high frequency current is calculated. At the peak of current, the contact gap center can generate an axial magnetic field of about 21 mT, the transverse magnetic field intensity is about 71 mT, and the axial magnetic field distribution is uneven. Secondly, due to the increase of iron core structure, the original divergent magnetic field can be bound into a certain space, and the magnetic field intensity in the contact gap can be enhanced. In this paper, an iron core structure is added between the inner and outer contacts, and the iron core structure is slotted. The simulation structure shows that after adding the iron core, the transverse magnetic field intensity increases by 1.22 mT, the maximum axial magnetic field intensity increases from 21.80 mT to 26.53 mT, the magnetic field intensity increases by 4.73 mT, the axial magnetic field distribution unevenness decreases from 8.90 to 7.39, and the magnetic field distribution becomes more uniform. Adding grooving treatment in the iron core structure increases the transverse magnetic field intensity in the contact gap by 0.25 mT, and the maximum axial magnetic field intensity also slightly increases by 0.49 mT, but the uneven distribution of axial magnetic field increases from 7.39 to 7.44, which is not conducive to the diffusion of vacuum arc. Finally, in order to further improve the strength and distribution uniformity of the magnetic field in the contact gap, this paper proposes a joint optimization method based on BP neural network and multi-objective intelligent optimization algorithm to optimize the contact model, establishes a BP neural network model with α, Δ, r, h and d as inputs and M, η and N as outputs, and optimizes the contact model through multi-objective intelligent optimization algorithm. The optimization results show that when the contact structure parameters α is 31.8°, Δ is 8.3 mm, r is 15.2 mm, h is 16.1 mm, and d is 1.1 mm, a transverse magnetic field of 74.99 mT is generated in the contact gap center. The axial magnetic field of 44.02 mT can be generated at the contact gap center of the peak current, and the unevenness is reduced from 7.44 before optimization to 4.67, which greatly improves the uniformity and improves the ability of magnetic field to regulate vacuum arc. © 2024 China Machine Press. All rights reserved.
