# Electromagnetic Actuator Design

### Key Takeaways

• Electric current serves as the actuating quantity in electromagnetic actuators.

• The most popular electromagnetic actuator is the electric motor.

• In electromagnetic actuator design, direct and associated inverse problems are formulated and analytical models are developed to validate one solution from the infinity set of solutions satisfying the application’s requirement.

The most popular electromagnetic actuator is the electric motor

Any device used to convert a control signal into controllable mechanical energy is called an actuator. Actuators are energy converters, and according to the input quantity or actuating quantity, actuators differ from each other. Depending on the principle that enables energy conversion, actuators are classified into hydraulic actuators, pneumatic actuators, thermal actuators, electrostatic actuators, or electromagnetic actuators.

Electromagnetic actuators are employed in various sectors of the automotive industry, industrial automation, and electrical protection systems. The actuating quantity in electromagnetic actuators is current. Electromagnetic actuator design is influenced by several factors such as reliability, cost-effectiveness, size, and the type of actuation needed.

## Electromagnetic Actuators

Electromagnetic actuators convert electrical energy to mechanical energy and vice versa. They work on the principle of electromagnetism. The actuating quantity in electromagnetic actuators is electric current. Electromagnetic actuator design and operation are governed by the following  fundamental laws:

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

1. Robust and reliable 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

## Types of Electromagnetic Actuators

If the actuating quantity is an electric current, the actuator is considered to be the electromagnetic type. For various applications, different types of electromagnetic actuators are used. The most popular electromagnetic actuator is the electric motor.

### Electric Motors

Electric motors are machines that convert electrical energy into mechanical energy. They consist of a stationary part called a stator and a rotating part called a rotor. When an electric motor is supplied by electrical energy, the stator produces a magnetic field, and the current-carrying rotor conductors placed in the magnetic field experience a torque. The rotor starts rotating based on the Lorentz force principle.

Electric motors can be classified into two main types, which are based on the nature of the actuating current:

1. DC motors - The actuating quantity is direct current in DC motors. DC motors are bifurcated into separately excited DC motors and self-excited DC motors. Types of self-excited DC motors are shunt motors, series motors, and compound motors.

2. AC motors - The actuating quantity is alternating current in AC motors. AC motors can be either single-phase AC motors or three-phase AC motors. Irrespective of the number of phases, AC motors are either induction motors or synchronous motors. Based on how the magnetic field is created in AC motors, they can be categorized as permanent magnet motors or electromagnetic motors. Permanent magnet motors rely on natural magnetic materials, whereas electromagnetic motors use materials that behave as magnets when current is allowed to flow.

### Solenoid Actuators

A solenoid is the simplest and most common electromagnetic actuator that produces linear or rotational motion by energy conversion. It consists of a soft iron core, a current-carrying coil, and an armature or plunger. The soft iron core is placed inside the current-carrying coil and the armature is positioned in the center of the coil. The coil induces a magnetic field when energized with the current. The magnetic field pulls the armature to the center of the coil.

Types of solenoid actuators are:

1. Linear solenoid actuators -  In linear solenoids, the movement of the plunger is linear.

2. Rotary solenoid actuators - Rotary solenoids utilize ball bearings to convert linear motion into rotary motion. The angular motion can be either clockwise or anti-clockwise.

Other examples of electromagnetic actuators are moving coil actuators and relays. Irrespective of the actuator type, the design approach for electromagnetic actuators is the same.

## Electromagnetic Actuator Design Approaches

The design of electromagnetic actuators is based on the requirements of the specific application. The electromagnetic actuator design process can be formulated as either a direct problem or an inverse problem.

### Direct Problem

In a direct problem, the structure, dimension, and composition of the electromagnetic actuator are known and certain characteristic values (for example, torque or flux density) are computed using numerical methods such as the finite element method. This approach of electromagnetic actuator design aids in designing steps without making a prototype, making it cost-effective.

### Inverse Problem

According to the characteristic values required by a specific application, the structure, dimensions, and composition of an electromagnetic actuator are designed. If the resolution of a direct problem is not satisfying, an associated inverse problem can be developed to solve the electromagnetic actuator design. The inverse problem approach may generate an infinite number of solutions for an electromagnetic actuator design.

In electromagnetic actuator design, direct and associated inverse problems are formulated and analytical models are developed to validate one solution from the infinity set of solutions satisfying the application’s requirement.

Cadence’s software can help design electromagnetic actuator circuits for given applications satisfying the imposed conditions. Subscribe to our newsletter for the latest updates. If you’re looking to learn more about how Cadence has the solution for you, talk to our team of experts.