What is the operating principle of electromagnetic relays?

Relays are some of the most versatile components in electronics and industrial systems. They allow control of current flow in electrical circuits by switching them between different configurations depending on the applied signal. Among them, electromagnetic relays stand out, whose operating principle is based on the phenomenon of electromagnetic attraction. They enable safe and efficient switching of circuits with different power levels, even in high-power systems.

An electrical relay is therefore an invaluable component in both classic electromechanical systems and modern industrial electronics.

Construction of an Electromagnetic Relay

An electromagnetic relay consists of several key components:

• Relay coil through which electric current flows;
• Iron core that strengthens the generated magnetic field;
• Movable contact (armature) that physically closes or opens the circuit;
• Spring, returning to the initial position after the current is disconnected;
• Enclosure providing insulation and protection against external conditions.

When current flows through the coil, a magnetic field is generated that attracts the movable contact. As a result, the electrical circuit is closed or opened, depending on the relay's design.

Operating Principle of an Electromagnetic Relay

The operating principle of a relay is relatively simple yet very effective. When electric current flows through the coil, a magnetic field is created that attracts the armature or other switching mechanism. This causes the relay contact to change state, allowing current to flow in the controlled circuit.

After the current is disconnected, the spring returns the contact to its original position, and the electromagnetic relay returns to its resting state. This mechanism allows control of circuits without direct contact with the load, increasing system safety and reliability.

Types of Relays

Relays come in various types, suited to specific applications:

• Electromagnetic relays – operate based on the magnetic field generated in the coil;
• Solid-state relays – use electronic components instead of a movable contact, increasing lifespan and allowing fast switching;
• Time relays – enable delayed circuit switching, e.g., in industrial automation systems;
• Electromechanical relays – classic devices with a mechanical contact and spring.

All these types allow control of low-power circuits while safely switching higher-power loads.

Function of a Relay in Electrical Circuits

The function of a relay is to separate the control circuit from the power circuit. In practice, this means a small electrical signal can turn large industrial devices, motors, or other loads on or off.

Electromagnetic relays also allow:

• protection of circuits against overload;
• fast disconnection in case of a short circuit;
• automatic control in industrial automation systems;
• electrical isolation between the input and output circuits.

Thanks to this, relays are a key component in many industries, from industrial systems to home and consumer electronics.

Relay Electrical Circuit

In a relay circuit, we distinguish two main elements:

1. Coil circuit – low voltage, controlled by a signal.

2. Contact circuit – high voltage, through which load current flows.

The current flowing through the coil generates a magnetic field that changes the state of the contact. Depending on the configuration, this may be an NO (normally open), NC (normally closed), or changeover contact. This allows safe control of industrial devices and electronics.

Relay Construction and Operating Principle Step by Step

1. Coil energization – applying voltage to the coil causes current to flow.

2. Magnetic field generation – the coil generates a field that acts on the movable contact.

3. Contact switching – the contact is attracted or repelled, closing or opening the electrical circuit.

4. Coil de-energization – disconnecting the voltage returns the contact to its original position thanks to the spring.

5. Final effect – the controlled circuit is closed or opened without physical contact between low and high voltage.

Applications of Electromagnetic Relays

Electromagnetic relays are used in a wide range of applications:

• Industrial automation – controlling motors, pumps, and conveyor systems;
• Consumer electronics – turning devices on and off using small control signals;
• Power industry – protection of high-voltage circuits and automatic switching;
• Timing and logic systems – implementing delays and control logic;
• Safety and isolation – separating control circuits from power circuits, preventing overvoltage.

In practice, relays allow control of large loads with a small signal, making them a key component in industrial automation and electronics.

Summary

An electromagnetic relay is a device that uses a magnetic field to switch electrical circuits. Its operating principle is based on current flow through the coil, which moves the contact and allows control of high-voltage circuits. Thanks to isolation between the control circuit and the load, relays are reliable, efficient, and essential in industrial systems and electronics.

We invite you to explore our offerings and discover how electromagnetic relays can increase the reliability and efficiency of your systems. Check our solutions and select components suited to your needs.