Electromagnetic relays are commonly made up of several key components, including an iron core, a coil, an armature, and contact springs. When a specific voltage is applied across the coil's terminals, current flows through it, creating an electromagnetic field. This magnetic force pulls the armature toward the iron core, overcoming the resistance of the return spring. As a result, the moving contact connected to the armature makes contact with the stationary contact, which is typically in an open state when the relay is not activated. This type of contact is referred to as a "normally open" (NO) contact.
When the coil is de-energized, the magnetic field disappears, allowing the spring to push the armature back to its original position. This action causes the moving contact to separate from the normally open contact and connect with another stationary contact, known as a "normally closed" (NC) contact. This switching mechanism enables the relay to control electrical circuits by either completing or breaking the connection.
Relays play a crucial role in electrical systems by acting as switches that can be controlled remotely. They are widely used in applications where low-voltage signals need to control high-voltage devices safely. The two main circuits involved are the control circuit, which carries the low-voltage signal, and the power circuit, which handles the higher current or voltage. This separation ensures that the control system remains isolated from the high-power components, improving safety and efficiency.
Understanding the function of normally open and normally closed contacts is essential for designing and troubleshooting relay-based circuits. By manipulating the coil's energization, engineers can control which contacts are open or closed, enabling complex automation and control systems. Whether in industrial machinery, home appliances, or electronic devices, relays remain a fundamental component in modern electrical engineering.
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