Investigation on DC interruption characteristics of three-electrode vacuum interrupter under Halbach transverse magnetic fields

• The three-electrode vacuum interrupter enables magnetically driven arc transfer. • Halbach transverse magnetic field guides the arc to the annular third electrode. • Complete arc transfer enables capacitor-assisted DC commutation. • Fast interruption achieved: 1000 V/920 A in 0.53 ms and 450 V/400 A in 2.35 ms. • Arc-transfer mode strongly depends on capacitor precharge and fault current level. A vacuum interrupter is the core component of a direct current (DC) circuit breaker, but DC interruption is challenging because there is no natural current zero. This paper investigates an arc-transfer DC interruption approach enabled by an annular Halbach transverse magnetic field and a three-electrode vacuum interrupter. An eight-magnet Halbach array provides a magnetic field exceeding 400 mT, which drives arc migration. Under a transverse magnetic field, the DC arc shows voltage oscillations, and the arc voltage can exceed the supply voltage, reaching 1.6 kV, which promotes current extinction. At high current, the arc can attach to the shield when the initial current exceeds 1 kA. Based on this phenomenon, the internal shield is redesigned as an insulated lead-out shield electrode along the migration path, connected to a precharged capacitor auxiliary branch. After the arc attaches to the lead-out shield electrode, the precharged pulse capacitor discharges into the auxiliary branch, generating an oscillatory current that forces a current zero and enables interruption independent of the main gap. Experiments demonstrate interruption of 1000 V and 920 A within 0.53 ms. The proposed three-electrode concept features a simple structure and a passive commutation interface, offering reliability and cost-effectiveness for DC interruption.