Electromagnetic trip unit

An electromagnetic trip unit, in which:

• the electromagnetic trip unit includes a trip lever, which can rotate around an longitudinal axis of the trip lever, the trip lever includes a trip lever body and a trip lever arm extending outward from the trip lever body;
• a rocker arm is connected to a movable core and can rotate around an axis of the rocker arm;
• the rocker arm includes a rocker arm body and a rocker arm knocking part extending from the rocker arm body;
• and
• a rocker arm positioning plate, which can also rotate around the rocker arm axis;
• the electromagnetic trip unit includes the movable core, an upper static core and a lower static core;
• the movable core can move relative to the upper static core and the lower static core in the upper static core and the lower static core;
• a movable core body end of a movable core body of the movable core faces and approaches the lower static core end of the lower static core, when the electromagnetic trip unit is not released, a first magnetic field air gap is formed between the end of the movable core body end and the lower static core end;
• the movable core body of the movable core is also provided with a movable core body step which causes a portion of the movable core body to have a larger diameter than that of the movable core body end along a moving direction of the movable core, when the electromagnetic trip unit is not released, a second magnetic field air gap is formed between the movable core body step and the lower static core end;
• the electromagnetic trip unit also includes a coil, which is arranged around the movable core;
• when the short circuit current flows through the coil, the movable core moves toward the lower static core under the attraction of the magnetic field, the motion of the movable core drives the rocker arm to rotate, the rotation of the rocker arm causes the rocker arm knocking part to act on the trip lever arm, thereby making the trip lever rotate around the axis of the trip lever to realize the release action of the electromagnetic trip unit;
• the electromagnetic trip unit also includes a magnetic field air gap adjustment assembly, the magnetic field air gap adjustment assembly includes the trip lever, a component that causes the trip lever to move along the axis of the trip lever, and the trip lever includes a trip lever bump, and the rocker arm positioning plate includes an inclined surface engaged with the trip lever bump, so that the linear motion of the trip lever drives the rotation of the rocker arm positioning plate;
• and a magnetic adjusting screw, wherein a threaded through hole is arranged on the rocker arm positioning plate, and the magnetic adjusting screw is engaged in the threaded through hole and connected with the rocker arm, so that when the linear motion of the trip lever causes the rotation of the rocker arm positioning plate, the rocker arm also follows the said rocker arm positioning plate to rotate, so as to drive the movable core to move relative to the lower static core, thus realizing the adjustment of the air gap of the first and second magnetic fields;
• the magnetic adjusting screw can be screwed in and out of the threaded through hole to move the rocker arm around the rocker arm rotation shaft, thereby the first and second magnetic fields air gap can be further adjusted;
• the first magnetic field air gap is smaller than the second magnetic field air gap.