Electromagnets : operating modes

Electromagnets, also known as electromagnetic actuators, are essential in many functions and uses of machines or control systems used in our everyday lives.

What is the role of an actuator? How does it work? You will see that in order to address some of their uses, electromagnets are subject to different standards and certifications.

Electromagnet operating principles and characteristics

What is an electromagnet ?

An electromagnet is a device that allows electrical energy to be converted into mechanical energy. To do this, an electrical current will travel along the electromagnet’s coil and generate a magnetic field, the attraction force of which allows for activating a mechanical movement through its mobile core.

The 3 elements of an electromagnet are :

• The magnetic circuit or inductor : represents the part containing the coil, which is generally static
• The copper coil : wound conductive wire that receives the electrical energy in order to create the magnetic field
• The armature/mobile core : the part attracted in the inductor against the static head

Once the electromagnet ceases to be supplied with the electrical current, the magnetic field is broken, and the mobile armature returns to its initial position when it comes into contact with a resistant force.

What are the action modes of an electromagnet ?

Electromagnets are defined in eight main categories :

• Linear : device in which the effect of the magnetic force is used to produce a rectilinear movement.
• Simple-effect : he movement from one end of the stroke to the other is ensured by the effect of the magnetic force and the return by exterior forces.
• Double-effect : the mobile armature has a different, so-called neutral position. The working stroke is made alternately in both directions, from the neutral position. The return to the neutral position must be ensured by exterior forces.
• Reversible : mobile armature without a neutral position. The working stroke is made alternately in both directions, from one end position to the other.
• Bistable : magnetic locking of the mobile armature in the two end positions, allowing for holding in position without power.
• Proportional : the magnetic force is proportional to the current circulating in the coil.
• Rotary :  device in which the effect of the magnetic force is used to produce a limited angular movement.
• Carrier : device in which the effect of the magnetic force is used to hold loads with ferromagnetic qualities.

Its operations are based on two modes :

• Pull action mode
• Push action mode

In pull mode, the electrical current crossing the coil will cause a magnetic flux that attracts the mobile armature. This attraction force will create a pulling movement that will move the load or the attached system.

Once power is lost, the mobile core returns to its original position under the effect of an exterior force (gravity, return spring, etc.).

With regard to push mode, when the coil is energized, a system or indeed a load is pushed by a through rod fixed to the mobile core (opposite the pulling side). Without power and as in the previous case the core returns to its starting position under the effect of an external force (gravity, return spring, etc.).

Standards and certifications : a gauge of electromagnet safety and reliability

Electromagnets and other actuators (holding devices, locks, etc.) can be employed for both common uses (locking access to buildings) and more critical ones (locking missiles). In all cases, the electromagnets must meet specific standards and certifications that attest to their reliability, durability and safety.

There are as many standards as there are market sectors and specific sub-fields, which guarantee that the actuators actually fulfil the requirements of the scope for which they are used.

In order to guarantee actuator compliance with current standards, tests and audits are performed frequently by laboratories or certifying bodies.
Compliance tests linked to the specifications are carried out on every actuator deemed as “critical” before delivery to the client.

Example standards :

• EN 9100, European standard describing a quality assurance system for the aerospace market.
• ISO 9001, international quality management system standard
• ISO 14001, standard guaranteeing the implementation of an effective environmental management system

The importance of an electromagnet is measured by its capacity to transform electrical energy into mechanical energy, produced via the magnetic field generated by the electromagnet.

This mechanical energy will be used to activate, hold or lock.

This is why actuators are of use in every market sector (industrial, medical, aeronautics, transport, buildings, etc.).

Secure, reliable, practical and modulable, electromagnets offer a wide scope for making movement processes easier.

Would you like us to help you with your development project? Mecalectro will take care of it.

Our recognized expertise and experience in the field of electromagnetic actuators enables us to offer standard ranges of electromagnets  and design specific solutions that are built to spec.