Low-voltage breaker

The invention discloses a low-voltage breaker, belonging to the technical field of low-voltage breakers. The low-voltage breaker comprises a shell, at least one circuit breaking and arc extinguishing device, an operation mechanism capable of cutting off or closing and a tripping device. The circuit breaking and arc extinguishing device comprises an arc extinguishing chamber component and a contact component. The arc extinguishing chamber component comprises a plurality of arc extinguishing grid plates and an arc isolating cover. Each arc extinguishing grid plate is provided with a basal part and a pair of extending legs extending from one end of the basal part, the arc isolating cover is provided with a pair of first wall bodies, a pair of second wall bodies and a pair of third wall bodies, a plurality of arc extinguishing grid plates form a contact cavity, the contact component corresponds to the contact cavity, and the second wall bodies correspond to the interior of the contact cavity. The invention is characterized in that the arc isolating cover also comprises a pair of inner walls, each inner walls is jointed with one end of each second wall body near the basal part of each arc extinguishing grid plate, the other end of each second wall body is jointed with each third wall body, and each inner walls is provided with grids. The invention prevents ablation of electric arcs to the extending legs, can protect the extending legs, prolongs the service life of the arc extinguishing chamber component, achieves fast arc extinguishing effect, and enhances the breaking capacity.