So, car relays can be seen as a collection of two parts: the control circuit for coil operation and the main circuit for contact operation. In the control circuit of a relay, there is only a small working current. This is because the contact capacity of the operating switch is small and cannot be used to directly control loads with high electricity consumption. It can only be controlled through the contacts of the relay to make and break.

When a certain voltage or current is applied to both ends of the electromagnetic relay coil, the magnetic flux generated by the coil passes through the magnetic circuit composed of the iron core, yoke, armature, and magnetic circuit working air gap. 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 force, the armature returns to its initial state, the normally open contact opens, and the normally closed contact closes.

The working principle of automotive relays mainly utilizes the principle of electromagnetic induction, which generates a magnetic field through the electrification of the coil, thereby controlling the closure and disconnection of the contacts. Specifically, when the coil is energized, it generates a magnetic field, and the moving iron is attracted to drive the contact spring, causing the static contact point to separate and the moving contact point to close. When the current of the electromagnetic coil is cut off, the iron core loses magnetism, the moving iron core resets under the action of spring force, the moving contact opens, and the stationary contact closes.

In addition, automotive relays are also widely used in scenarios such as automatic regulation, safety protection, and conversion circuits. In cars, relays usually need to be able to withstand harsh environmental conditions such as high and low temperatures, sand and dust, water, salt, oil, etc., as well as vibration and impact.