Solenoids – Overview and Types

What are Solenoids?

solenoidsSolenoids are among the very simple electrical components that have huge impacts on everyday life. The name itself is derived from the Greek term solen, which describes a pipe or a channel. The second half of the name is derived from the Greek term eidos, which refers to a shape. Essentially, a solenoid is an electrical component in the shape of a pipe.

Solenoids are utilized in a variety of different applications, and there are many different types of solenoid designs available. Each of them has its own particular properties that make it useful in a specific application or in many specific applications.

The different designs of solenoids do not change their essential operating feature. Solenoids, though they are designed in many different ways, generally function on the same electrical principle, but their mechanical energy is distributed differently in different designs, allowing them to be used on a broader range of devices and designs.


How Do Solenoids Work? What is the Physical Principle?

The principle behind any solenoid has to do with magnetism. Electricity and magnetism are combined by physicists into electromagnetism – the relationship is so strong that this is necessary – and electromagnetism is one of the four fundamental forces of the universe.

A solenoid is a very simple device. It generally consists of a coil of wire that is wrapped around a core made out of metal. This has the effect of making a uniform magnetic field when a current is applied to it. Electricity converts to magnetism, magnetism converts to electricity and, hence, these two forces are combined into one. An interesting thing about the uniform field in a solenoid is that, if the solenoid was an infinite length, the magnetic field would be the same anywhere along the component.

Anybody with experience with magnetism understands just how powerful this force can be. In a solenoid, this translates to these sometimes very small electrical components being able to do a tremendous amount of work. For example, a powerful solenoid can easily slam shut a valve that would be challenging for even the burliest plumber to close manually.

By altering the direction of the mechanical force that a solenoid produces, rotary applications and other types of applications can be accommodated. This makes these extremely flexible devices that make some of the most common electrical components and appliances possible. This very simple device can make limitless complexity possible.


Who Invented Solenoids?

The solenoid was invented by Andre–Marie Ampere, whose name may be familiar to anybody who knows anything about electronics. The unit of current, the ampere, is named after the same individual. He was active in the 19th century and one of the most significant of all early electrical inventors.

What Kinds of Applications use Solenoids?

Solenoids have many different applications. The primary type of application that they are used in, however, is one that takes advantage of the fact that the metallic slug in the middle of the solenoid can be driven forward or backward by the application of electric current. This has some very powerful implications.

A solenoid can be used to electrically control a valve, for instance, by using the solenoid core to apply mechanical force to the valve. They can also be used in specific types of door locking mechanisms, which utilize an electromagnet and provide an extremely secure closure. You may be familiar with some of these devices. If you've ever passed through a door that emitted a loud buzz before it opened, you heard a solenoid driven lock in action.

Solenoids are used in many different products and appliances. You'll find them in computer printers, you'll find them in the fuel injection equipment used on cars and you'll find them in many different industrial settings.

Another advantage of the solenoid as a component is that, when electricity is applied, the reaction is instant. This means, for example, in a high security situation a door that uses an electromagnetic lock that is driven by a solenoid can be locked instantly.

That fast response is one of the most important factors in determining the different applications for solenoids. For all practical purposes, the time between an electrical current being applied to a solenoid and the device reacting with the predictable movement of the core is instantaneous. This means that they are particularly valuable in any application where lightning fast reactions to a given state are imperative. For example, in a situation where a particular line of pipes may leak heated steam into an environment where workers may be burnt, having a solenoid operated valve that can react under those conditions and instantly close down that line is imperative.

The same is true in situations where, rather than something being closed, something needs to be opened. For example, a solenoid can be used on electrical contacts and, under certain circumstances, the solenoid can be used to pull the contacts apart from one another so that the electricity across the circuit is disrupted.

Solenoids – like transformers, capacitors and other basic electrical components – are found in a tremendous variety of different applications. They are, in reality, too numerous to even list. This is one of the most basic electrical components in the world and has one other quality that makes it particularly useful in rugged industrial conditions.

Solenoids are simple. That is a tremendous strength where electrical components are concerned. A well–built solenoid can operate for hundreds of thousands of cycles. If you consider the fact that in emergency valve may only be tripped once or twice in the entire lifetime of the equipment to which it is affixed, you can easily see how much value there is to be had in these components. Solenoids have the very unusual quality of being able to provide extremely mission–critical functionalities in a device that is nothing close to what could be called expensive, exceptionally reliable and that is capable of lasting for literally decades before it needs to be replaced with a new device.


What Types of Solenoids Exist?

Description: Solenoids in pipesThe many different types of solenoids available all have a place in industrial and other usages. They vary in terms of their design, th ere function and the materials of which they are made, but they are all based on the same electrical principles that drive the basic solenoid.

Most of the variations on solenoid designs involve using either AC or DC power and altering the direction of mechanical force that the solenoid exerts. This can allow the devices to be used in any application where instantaneous mechanical force needs to be exerted to close a valve, lock a door and so forth.

While there are different types of solenoids on the market, they're all variations on the core principle that makes solenoids work. Whether they are installed on pipes and provide a fast and safe way to close the valve, installed in a car ignition so that the contacts that actually power the vehicle can be brought together or installed in any other capacity, they are largely the same devices with some variations allowing for customized applications.


What is a AC Laminated Solenoid?

Description: AC Laminated SolenoidAn AC laminated solenoid is notable for the amount of force that can be executed in their initial stroke. They can also utilize a longer stroke than a DC solenoid. They are available in many different configurations and sizes. These are one of the types of solenoids that emit an audible hum when they are being used.


What is a DC C–Frame Solenoid?

DC C–Frame solenoid utilizes a single frame, shaped like the letter C, which is wrapped around the coil. These have a wide variety of different applications. Although they are noted here in a DC configuration, they can also be manufactured to be utilized with AC power.


What is a DC D–Frame Solenoid?

DC D–Frame solenoid components have a two-piece frame that is wrapped around the coils. These are utilized in many different applications, including industrial applications. Like their C–Frame cousins, these can also be manufactured in AC variants, for applications when the properties of an AC solenoid are more desirable than a DC solenoid.


What are Holding Magnets?

Holding magnets are used for just what the name implies. These magnets are used to either hold materials or a mechanical device in a certain position. These are oftentimes utilized in manufacturing processes and, to some degree, they may also be used in food processing. Holding magnets can be used to remove metallic impurities from food or other materials and hold it in place so that it does not fall into the material being purified.


What is a Linear Solenoid?

Description: AC Laminated SolenoidLinear solenoids are the types that most people are likely familiar with. These are capable of exerting a pushing or pulling force on a mechanical device and can be used for various metering functions.

Linear solenoids are used in a variety of different applications. For example, there is a solenoid on the starter apparatus of a motor vehicle. When electrical current is applied to the solenoid, the solenoid moves – generally in a linear fashion – to bring two contacts together. When these contacts are brought together, they allow power to flow from the battery to the various components of the vehicle and the vehicle to start.

Linear solenoids are also utilized in applications such as electric locks. The linear solenoid can be thrown when voltage is put through it and, when it is attached to the heavy bolt that goes through the receptacle on a doorframe, it can instantly secure a door enough to hold up to a great deal of abuse.

Linear solenoids are the easiest ones to understand, as the coil and the core are generally arranged exactly as one would expect and there is little variation from theory to the actual design of the device.


What is a Rotary Solenoid?

A rotary solenoid provides a great example of how mechanical force can be utilized in different ways to facilitate the automated control of processes and, quite simply, to make life easier.

In a rotary solenoid, there is the same coil and core configuration, though it is slightly altered. In a rotary solenoid, instead of the solenoid being a simple device with a coil and a core, there is a disc involved. The core is mounted in the center of this disc and there are grooves cut on the bottom of the disc. The solenoid body is lined up with these grooves and there are ball bearings used to facilitate easier motion.

Activating the solenoid causes the core to be drawn backward into the coil. This force is translated to rotation force in the disc. Most of these devices are also equipped with a spring. When the power is removed from the solenoid, the spring causes the core to be drawn out of the coil, releasing the disc and sending it back to its original position.

Like many electrical devices, this device happens to have been developed as a defense product. It was first utilized during World War II as a way to increase the durability of the devices utilized in bombs. Today, these types of solenoids are common electrical components, which are very heavy duty and very suitable for use in trying industrial environments.


What is a Tubular Solenoid?

It should come as no surprise that electrical components – even those as sturdy and simple as a solenoid – need to be protected under certain working conditions. A tubular solenoid provides a way to provide that protection and to still get the classic push pull function of a solenoid.

In a tubular solenoid design, a standard solenoid is encased in a solid metal tube. This allows the device to be safely installed in a variety of different appliances and components and, of course, also provides a great deal of protection for the device so that its longevity can be assured.

Tubular solenoids are most common in DC applications. They are inexpensive devices that can be utilized whenever a standard push pull/plunger design is required for a solenoid application.