VACUUM CIRCUIT BREAKER

In a vacuum circuit breaker having at least a pair of electrodes which generate an arc when detached from each other in a high vacuum tank, said electrodes are made of a copper alloy containing a low-melting-point substance and opposing contact surfaces each in the shape of a ring are placed along the periphery of the electrodes. The electrodes have about two to four grooves extending from the peripheral edge of the contact surfaces to the internal surfaces of the electrodes which are maintained detached from each other, whereby current paths in the electrodes are formed almost in parallel with the contact surfaces of the electrodes over a certain length from an arcing point in the peripheral direction at the time of ignition, thus self-driving the arc in the peripheral direction. The electrodes have on the back side thereof reinforcing materials which are mechanically strong enough to make up for the lack of the mechanical strength required for the electrodes and which are sufficiently low in electric conductivity compared with the electrode materials to such a degree so as not to allow the intensity of the magnetic field to drop to a point lower than a level required by the electrodes.