What is the working principle of an automotive relay?
2 Answers
Automotive relay working principle: Simply put, it refers to energizing the relay coil, which generates magnetic force. This magnetic force attracts an iron piece containing a switch to achieve a switching function. Here is a detailed explanation: 1. A relay is both a control switch and a controlled object (actuator). Taking the fuel pump relay as an example, it is the control switch for the fuel pump. However, the coil of the fuel pump relay can only form a circuit through the grounding point of the electronic control unit when the driving transistor in the electronic control unit is turned on. 2. When a certain voltage or current is applied to both ends of the relay coil, the magnetic force generated by the coil acts through the magnetic circuit composed of the iron core, yoke, armature, and working air gap. Under the influence of the magnetic field, the armature is attracted to the pole face of the iron core, thereby pushing the normally closed contacts to open and the normally open contacts to close. When the voltage or current at both ends of the coil is below a certain value, the mechanical reaction force exceeds the electromagnetic attraction force, causing the armature to return to its initial state, with the normally open contacts opening and the normally closed contacts closing.
The working principle of automotive relays is actually quite interesting. It's like a little helper in the car that controls high-current components. Simply put, when you press a button, such as turning on the headlights or starting the engine, a small current signal flows through the coil inside the relay. This coil instantly generates a magnetic force, pulling the internal metal contacts to close, thereby allowing another high-current circuit to connect, which powers the headlights or turns the starter motor. Relays are designed to prevent small switches from being damaged by high-voltage currents. For example, after a small current controlled by an in-car switch triggers the relay, the relay safely transmits the power. In modern cars, such relays are ubiquitous, such as in fans or audio systems. If a relay fails, the circuit will break, with symptoms like headlights flashing once and then turning off or the engine not starting. Although you might not notice its presence while driving normally, its efficient operation makes the car's electronics more stable and durable. It's recommended to learn a bit more about this, as it can help you perform simple roadside troubleshooting.
