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Electromagnetic Actuators in Mechatronics

Key Takeaways

  • An actuator takes a control signal and responds to it by converting that signal into controllable mechanical energy. 

  • An electromagnetic actuator works on the principle of electromagnetism, and converts electrical energy into mechanical energy and vice versa. 

  • Electromagnetic actuators are reliable and robust, simple to manufacture and mass produce, and easily integrate in mechatronic systems. 

Electromagnetic actuator

Electromagnetic actuators and sensors are common in most mechatronic systems

Mechatronics is an interdisciplinary branch of engineering that has helped the evolution of modern technology. Systems that combine electrical, electronics, and mechanical engineering applications are categorized as mechatronics. Electromagnetic actuators and sensors are two critical components in most mechatronic systems.

Let's take a closer look at mechatronic systems, and the role actuators play in them. 

Actuators

Actuators are devices used to convert a control signal into controllable mechanical energy. There are different types of actuators that are classified by how they enable energy conversion. The types of actuators commonly seen in industrial and commercial applications are:

  • Hydraulic actuators
  • Pneumatic actuators 
  • Thermal actuators
  • Electrostatic actuators
  • Electromagnetic actuators

Actuators are just energy converters, and according to the input quantity or actuating quantity, each actuator mentioned above is different from one another. The actuating quantity in the thermal expansion actuator is temperature, it is voltage in the magnetostrictive actuator, charge in the piezoelectric actuator, and current in the electromagnetic actuator.

Electromagnetic Actuators

Electromagnetic actuators work on the principle of electromagnetism. Energy converts from electrical to mechanical and vice versa. The electric current serves as the actuating quantity in electromagnetic actuators.

 The fundamental laws governing electromagnetic actuators are:

  1. Faraday’s laws of electromagnetic induction.
  2. Lorentz force of electromagnetic forces.
  3. Biot-Savart’s Law.

Advantages of Electromagnetic Actuators

  1. Reliable and robust operation.
  2. Easy to manufacture and mass produce.
  3. Easy integration in mechatronic systems.
  4. Compatible in harsh environments such as high temperatures or vacuums.
  5. High force density and acceleration.

Electromagnetic Actuators in Circuit Breakers

Protective relays in circuit breakers are a classic example of an electromagnetic actuator. A protective relay detects faults and enables the circuit breaker to isolate the rest of the circuit from the fault. These relays are classified into two types based on use.

Electromagnetic Attraction Relays - Electromagnetic attraction relays are further divided into attracted armature relays, solenoid relays, and balanced beam relays. Electromagnetic attraction relays actuating quantities can be either ac or dc.

Electromagnetic Induction Relays - Any relays that utilize electromagnetic induction fall under this type of relay. Ac quantities are used to actuate electromagnetic induction relays. 

Solenoid Relays 

A solenoid relay utilizes a solenoid and a movable iron plunger to operate a circuit breaker. The plunger being drawn to the relay coil or solenoid operates on the principle of electromagnetic attraction.

Under healthy circuit conditions, the current through the relay coil (solenoid) is less than the pick-up value. This causes the plunger to be held down either by gravity or a spring. The downward position of the plunger will not allow current through the trip coil, so the circuit breaker will remain in the closed position. However, under faulty conditions, the circuit breaker will open.

Under faulty current conditions, the heavy current flowing through the circuit makes the current flowing through the relay coil greater than the pick-up value. As a result, the plunger is drawn towards the relay coil, and this upward movement allows the current through the trip coil. When the trip coil is energized, the circuit breaker will open.

Designing a Mechatronic System

When designing a mechatronic system, it is almost impossible to avoid actuators. If the actuating quantity in the system is an electric current, then the actuator of choice will be an electromagnetic actuator. Cadence’s software can help design electromagnetic actuator circuits for industrial and household applications.

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