The basic information and introduction about electromagnetic switch

The electromagnetic switch, as the name implies, is a switch controlled by an electromagnet, which is a combination of an electromagnet and a switch. When the electromagnet coil is energized, electromagnetic attraction is generated, and the movable iron core pushes or pulls the switch contact to close, thereby turning on the controlled circuit. Electromagnetic switches have a wide range of applications in various industries, and the most common is the contactor in the industrial field. The electromagnetic switch is the control switch on the starter. It is one of the three major components of the starter (DC motor, transmission meshing mechanism, electromagnetic switch). The transmission meshing mechanism makes the starter pinion move forward and meshes with the engine flywheel ring gear. On the other hand, it pushes the switch contact to connect, so that the DC motor is energized to run, thereby driving the engine to start.
Basic Information
The starter electromagnetic switch is the key component of the starter, and the design quality of the electromagnetic switch directly affects the reliability of the starter.
The electromagnetic switch of the starter has two functions. One is to connect the main circuit to make the starter rotate, and the other is to push the drive gear out through the fork to mesh with the gear ring of the engine flywheel. Therefore, the electromagnetic switch is required to have a corresponding suction force and a corresponding stroke. , The contacts can reliably make and break large currents. In addition, it is also required to reduce the volume and weight as much as possible.
Based on the above characteristics, the contact structure of the electromagnetic switch generally adopts the contact form, that is, the movable contact is made into a bridge or disc shape, so that it has a larger heat dissipation surface and heat capacity. Most of the magnetic system adopts solenoid type electromagnet structure to meet the requirements of corresponding stroke, corresponding suction, small size and light weight.
The moving iron core of the electromagnetic switch can move smoothly in the brass bushing equipped with solenoid coils. The moving iron core rod is connected by the fork unidirectional device. Under the action of the return spring, the moving iron core is usually kept at the initial non-working position. When starting, the drive gear of the starter should move forward about 12-20mm. Therefore, when the electromagnetic switch starts to attract, a large magnetic potential is required to generate the necessary initial suction. After the suction, the air gap is reduced. , The electromagnetic attraction force increases sharply, which greatly exceeds the force required to maintain the attraction state. For this reason, the electromagnetic switch adopts two coils (attracting coil and holding coil). At the beginning, the attracting coil and the holding coil generate electromagnetic attraction. When the switch contacts are attracted, the attracting coil is automatically out of the working state, and the holding coil is used alone. To keep the switch in the closed state, keep the coil current relatively small, it can be wound with a thinner wire, so that the volume of the electromagnetic switch can be reduced, and a reasonable suction matching can be achieved. In order to ensure the reliability of the starter, it is necessary to focus on the design quality of the electromagnetic switch.

Post time: Sep-13-2021