The electromagnetic switch is composed of an attracting coil, a holding coil, a movable iron core, a return spring, and a main contact.It has the functions of controlling the engagement and separation of the starter drive gear and the engine flywheel ring gear, and controlling the connection and disconnection of the DC motor circuit.
The working process of the electromagnetic switch is
1. Turn the ignition switch to the start position, connect terminal 50, the suction coil passes through the main contact C, the excitation winding, and the armature rotor are energized. Keep the coil directly grounded and energized.
2. The magnetic fields of the two coils have the same direction, and together overcome the elastic force of the return spring to attract the movable iron core, thereby pushing the shift fork to mesh the drive gear with the flywheel rack of the engine, and at the same time connect the main contact of the starter.
3. The main contact is connected, the excitation winding of the starter and the armature rotor are energized at the same time, driving the flywheel of the engine to complete the starting action.
4. When the main contact of the starter is turned on, the suction coil is short-circuited, and only the holding coil keeps the iron core in action.