How thermomagnetic actuators work

Learn about thermomagnetic actuators, how they work, their advantages and limitations, and the different types available in this informative article.

How Thermomagnetic Actuators Work

Thermomagnetic actuators are devices that utilize the thermal expansion of materials in response to an applied magnetic field. These actuators are used in a variety of applications, from controlling valves and dampers to adjusting mirrors in optical systems.

Basic Principles of Thermomagnetic Actuators

Thermomagnetic actuators consist of a magnetic circuit and a thermal element. The magnetic circuit is typically made up of a soft magnetic material, such as iron or steel, and is designed to provide a path for the magnetic flux. The thermal element is made up of a material with a large coefficient of thermal expansion, such as a shape memory alloy or a bimetallic strip.

When an electrical current is applied to the coil of the actuator, a magnetic field is generated. This magnetic field causes the magnetic circuit to become magnetized, which in turn causes the thermal element to heat up due to eddy currents generated within it. The heating of the thermal element causes it to expand, which in turn causes the actuator to move.

The direction of the movement of the actuator depends on the orientation of the magnetic field and the design of the magnetic circuit. By changing the direction of the current in the coil, the direction of the magnetic field can be changed, which allows the actuator to be controlled.

Applications of Thermomagnetic Actuators

Thermomagnetic actuators have a wide range of applications, including:

  • Controlling valves and dampers in HVAC systems
  • Adjusting mirrors in optical systems
  • Actuating microelectromechanical systems (MEMS)
  • Actuating switches and relays
  • Positioning sensors

One of the advantages of thermomagnetic actuators is their ability to provide precise and repeatable movements. The movement of the actuator is directly proportional to the change in temperature of the thermal element, which can be accurately controlled by the amount of current applied to the coil.

In addition, thermomagnetic actuators are simple and reliable devices that require minimal maintenance. They do not have any wearing parts, such as gears or bearings, that require regular replacement, and they can operate in harsh environments where other types of actuators may fail.

Overall, thermomagnetic actuators are a versatile and reliable type of actuator that are used in a wide range of applications. Their ability to provide precise and repeatable movements, combined with their simplicity and reliability, make them a popular choice for many different industries.

Types of Thermomagnetic Actuators

There are several types of thermomagnetic actuators, each with its own unique design and operating characteristics. Some of the most common types of thermomagnetic actuators include:

  • Bimetallic actuators: These actuators consist of two layers of metal with different coefficients of thermal expansion that are bonded together. When heated, the layers expand at different rates, causing the actuator to bend.
  • Shape memory alloy (SMA) actuators: These actuators are made from materials that exhibit a shape memory effect, where they can be trained to return to a specific shape after being deformed. When heated, the SMA material returns to its trained shape, causing the actuator to move.
  • Electromagnetic actuators: These actuators use a magnetic field to generate a force that moves a piston or other mechanical element. The thermal element in these actuators is used to control the magnetic field, rather than to directly generate motion.

Advantages and Limitations

Thermomagnetic actuators offer several advantages over other types of actuators, including:

  • Precision and repeatability
  • Simple design
  • Reliability
  • No wearing parts
  • Ability to operate in harsh environments

However, there are also some limitations to thermomagnetic actuators that should be considered when selecting an actuator for a specific application. Some of these limitations include:

  • Low force output compared to other types of actuators
  • Slow response time due to thermal lag
  • Low efficiency due to the need for electrical heating
  • Limitations on the range of motion and displacement that can be achieved


Thermomagnetic actuators are a unique type of actuator that utilize the thermal expansion of materials in response to a magnetic field to generate motion. They offer several advantages over other types of actuators, including precision, reliability, and the ability to operate in harsh environments. However, they also have some limitations, such as low force output and slow response time, that should be considered when selecting an actuator for a specific application.