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Machine Compare

Solenoid fundamentals 101: A useful guide to aid your selection

30 May 2021

Solenoids can be found everywhere, but most go unnoticed. Their simple design has transformed many aspects of our lives – helping us wash our dishes, brew our morning coffees and keep us and others safe by allowing us to break our cars in front of traffic lights. So, what exactly are they and how do they work? We’ve laid it all for you.

What are solenoids?

Derived from the Greek words ‘solen’ (pipe) and ‘Eidos’ (coil), solenoids are electromagnetic devices that convert electrical current into mechanical energy. Solenoids are generally designed by tightly wounding wires in a helix shape around a piece of metal. The basic composition of solenoid includes a coil of wire, the housing and a movable plunger or armature. Once electric current passes through it, this creates a magnetic field, creating linear motion.

With the electric current introduced and the magnetic field formed around the coil, this draws the plunger in and, hence, mechanical energy is created. This movement becomes possible as the magnetic field created has a positive and negative pole that attract and repel material sensitive to magnets. In a solenoid, the electromagnetic field causes the piston either to move backwards or forwards.

 Benefits of solenoids

The main benefits of solenoids include their high reliability, cost-effectiveness and longevity. On top of this, solenoids’ high versatility makes them suitable for use in a vast range of applications including in industries like dental, appliance, energy, medical and transportation.

What’s more, solenoids typically operate fast, are reliable and tend to be easy to install and maintain. Solenoids also generally offer more consistent electrotechnical force over a long period and tend to be affordable.

Different types of solenoids

There are a range of different solenoids out there, suitable for various industrial applications, including:

Linear solenoids

Linear solenoids are composed of wire coil wrapped in a corkscrew around movable metalcore. This type of solenoid’s smooth motions make it perfect for applications such as automatic security door mechanisms and starter motors.

Tubular solenoids

Like linear solenoids, tubular solenoids create a push-pull force on a metallic core. The difference is that tubular solenoids are encased in metallic sleeves instead of movable metals slugs, lessening the magnetic flux leakage. Tubular solenoids are great for ‘long stroke’ appliances such as hydraulic valves, steering controls and current-limit switches.

Rotary solenoids

In this type of solenoid, the magnetic force is converted into rotational force or motion. Rotary solenoids consist of an armature core mounted on a flat disk. Once current is introduced, the armature is attracted towards the stator and the flat disk rotates.

Two other differences worth considering include:

AC laminated solenoids

AC laminated solenoids have a very high initial attracting force and short closing time. These are made with laminated metal or insulated thin sheets which are individually assembled. Due to their characteristics, AC laminated solenoids are used in electronic devices requiring immediate action like medical equipment. Locks, industrial machinery and domestic appliances are other applications.

DC D-frame solenoids 

This type of solenoid has a coil that is covered by two ‘D’ frames on two sides. Typical applications include AC power applications. 

When choosing a solenoid, here are some things to consider:

When choosing a solenoid, here are some things to keep in mind:

Solenoid size. Identify the available space into which the solenoid will be installed – including length, width and height.

The direction of motion required. Solenoids are designed to either provide a push or pull or rotary movement. Define which one fits your given application.

Operating stroke. The amount of force a solenoid can generate decreases exponentially with the distance that the solenoid plunger (armature) must travel. Smaller/shorter solenoids provide short strokes (< .25”), and larger/longer solenoids can provide more stroke (< 2”). You need to estimate how much mechanical movement will be required to achieve the desired result in your application.

Actuation force. This is commonly defined as the minimum amount of force required at the longest stroke in your application. You need to estimate how much force will be required to achieve the desired result in your application.

Duty cycle. This is the amount of time the solenoid is energized (ON) versus the time it is de-energized (OFF). The first step toward identifying the Duty Cycle your application may require would be to estimate how much time the solenoid must be energized (ON) in order to perform the required function. From a size perspective, a shorter duty cycle will enable one to achieve more pull-in force, at a longer stroke, for a given size solenoid, which may help to resolve size constraints in your application.

Environmental considerations. This includes ambient temperature and humidity/moisture and dust. Consider the ambient temperature in which the equipment you are designing will operate. It is also important that you define what level of humidity (moisture), and dust protection your application will require so that the most cost-effective solenoid design can be selected.

Popular solenoid categories on Marketplace 

There’s a range of different solenoids listed on Marketplace. Let the links below guide you or use the simple search tool on the site. Or why not take a shortcut? View all solenoids currently listed on Marketplace by clicking here. Don’t forget, as a first-time user on the site, you can claim an exclusive 5% off your first order – that includes the whole basket. Claim your discount here.

On top of helping you find the right solenoid, we want to make your spare parts buying process future-proof. Discover our 8 crucial tips on how to streamline the purchasing process and save money while doing so.

Brand or Seller Product name Manufacturer Code
UCIC Festo Air Solenoid Valve, 5/2, Spring Return, Monostable, 2.2-8 Bar, G 1/4, MFH Series

























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