The invention discloses an electric mounting device, especially a circuit protective switch or a motor protective switch. Wherein, said device comprises a frame with a connecting element for connecting the conflux row and/or connecting wire on at least one end; at least one switch contact point with a fixed switch contact element and a movable switch contact element, while they are broken, an electric arc will be generated in the electric arc pre-burn room; said electric arc via the arc guide rail will enter into one arc eliminator with limited current; the electric arc pre-burn room has pre-burn plate to form a reflux channel between the frame and the pre-burn plate, the arc eliminator and the electric arc pre-burn room; the part of frame inside the pre-burn plate has a groove which can be contacted from outer space, to be embedded with iron plate to attain high AC power, and embedded with permanent magnetic plate for attaining high DC power.