An electromagnetic system includes a magnetic yoke, a coil mounted in the magnetic yoke, a lower iron core disposed in a lower portion of the coil, a top plate disposed above the coil, an upper iron core having a lower portion disposed in the coil and an upper portion extending through the top plate, an armature disposed above the top plate and fixedly connected to the upper iron core, a magnetic isolation ring disposed between the upper iron core and the top plate, and a plurality of balls each rolling in one of a plurality of first curved grooves of the armature and one of a plurality of second curved grooves of the top plate. The upper iron core moves in a vertical direction. A force applied on the armature by the ball is inclined to a central axis of the upper iron core to drive the armature to rotate.