What is the working principle of automotive relays

The working principle of the automotive relay: Generally speaking, the coil of the relay is energized, and then the coil generates magnetic force, which attracts the iron sheet with the switch to realize the function of the switch.

When a certain voltage or current is applied to both ends of the coil of the electromagnetic relay, the magnetic flux generated by the coil passes through the magnetic circuit composed of the iron core, the yoke, the armature and the working air gap of the magnetic circuit. Under the action of the magnetic field, the armature is Attracted to the pole surface of the iron core, thereby pushing the normally closed contact of the contact to open, and the normally open contact to close; when the voltage or current at both ends of the coil is less than a certain value, and the mechanical reaction force is greater than the electromagnetic attraction, the armature returns to In the initial state, the normally open contact is disconnected and the normally closed contact is connected.

Then the automotive relay can be regarded as a collection composed of two parts: the control circuit working with the coil and the main circuit working with the contacts. In the control circuit of the relay, there is only a small working current. This is because the contact capacity of the operation switch is very small and cannot be used to directly control the load with large power consumption. It can only be controlled through the contacts of the relay.

The relay is both a control switch and a control object (actuator). Take the fuel pump relay as an example, it is the control switch of the fuel pump, but the coil of the fuel pump relay can only form a loop through the grounding point of the electronic control unit when the triode is turned on in the electronic control unit.