Solenoid

Jai Ganesh · 2025-01-25 16:57:53

Solenoid

Gist

A solenoid is a type of electromagnet formed by a helical coil of wire whose length is substantially greater than its diameter, which generates a controlled magnetic field. The coil can produce a uniform magnetic field in a volume of space when an electric current is passed through it.

Summary

The Greek word “Solen” from which the English word “solenoid” derives, means “channel” or “pipe.” Soldering irons are utilised in both industrial and domestic equipment. They come in a range of shapes and sizes, each with a unique set of uses. Despite the fact that the application changes, the underlying working principle remains constant.

What is Solenoid?

A solenoid is a coil of wire, often cylindrical in shape, that functions as a magnet when it is carrying a current, attracting a movable core into the coil as the current passes. Solenoid switches and controls mechanical devices and it is particularly useful as switches or controls in mechanical devices (such as a valve).

Working Principle of Solenoid

* Electromagnetic phenomena make the solenoid work. Putting a metal core inside the coil makes the magnetic lines of flux focus on the core, which increases the coil’s induction. This is because the magnetic lines of flux aren’t spread out across the whole coil.

* Only the coil’s centre receives the vast majority of the flux and only a small amount of flux remains at the coil’s end.

* To enhance the magnetic strength of a solenoid, you can do one of two things: either increase the density of its turns or increase the amount of current passing through it.

* As with all magnets, the active solenoid is composed of two poles: a positive and a negative pole, to attract or repel objects, respectively.

Function

* During the passage of electric current through the coils of a solenoid, a magnetic field is generated.

* The number of coils that the solenoid has an effect on the strength and amplitude of the magnetic field generated by a solenoid.

* Solenoid armatures can move in response to the voltage applied to the coils, increasing the flux coupling between the coils and the armature.

* It accomplishes this by bridging the air gap that exists between the two cores.

* The movable core, also known as the armature, is spring-loaded, which means that when the voltage to the solenoid is turned off, the armature retracts to its original position.

Types

* AC Laminated Solenoid

** The metal core and wire coil make up an AC laminated solenoid. Composite metal cores are used to reduce stray currents and improve the solenoid’s performance.

** The AC laminated solenoid has the benefit of delivering a large force on the initial stroke. They come in various sizes and generate a clear buzzing sound while in use.

** Medical equipment, locks, cars, industrial equipment, printers and various household appliances all use AC laminated solenoids.

* DC C-Frame Solenoid

** The particular C frame pertains to the design of the solenoid. It is merely a C-shaped frame by which the coil is surrounded.

** Several daily applications have made use of the DC C-Frame solenoid, which is distinguished by its controlled stroke. Despite the fact that they are classified as DC, their application can be found in equipment that is powered by alternating current.

* DC D-Frame Solenoid

** A two-piece frame protects the coils.

** On AC power, the D-frame solenoid has a controlled stroke just like a C-frame solenoid.

Application

* Solenoids are used in a wide range of applications, ranging from electronic hobbies to household appliances and beyond.

* A common application for these devices is an electric lock or latch, which requires an automatic on/off feature to function properly.

* Solenoids are also commonly found in a variety of appliances throughout your home or office, such as your washing machine and copy machine, among other places.

* They are found in a variety of applications, including automobiles and pinball machines.

* When we apply current to a solenoid, the magnet becomes even more powerful. When it comes to locking mechanisms, solenoids are widely used. Door locking in hotels, offices and secure areas, vending machines, remote access systems, turnstiles, car parks and access obstacles are just a few of the obvious applications.

Conclusion

Solenoids, their operation and the many types of solenoids on the market should all be familiar concepts by this point. It is simple and effective to use solenoid valves, electromagnetic switches and mechanical interlocks to control valves and electromagnetic switches. When it came to applications that required a lot of power in a compact space, they were the best option because of their immediate response and their ability to operate reliably.

Details

A solenoid is a type of electromagnet formed by a helical coil of wire whose length is substantially greater than its diameter, which generates a controlled magnetic field. The coil can produce a uniform magnetic field in a volume of space when an electric current is passed through it.

André-Marie Ampère coined the term solenoid in 1823, having conceived of the device in 1820. The French term originally created by Ampère is solénoïde, which is a French transliteration of the Greek word σωληνοειδὴς which means tubular.

The helical coil of a solenoid does not necessarily need to revolve around a straight-line axis; for example, William Sturgeon's electromagnet of 1824 consisted of a solenoid bent into a horseshoe shape (similarly to an arc spring).

Solenoids provide magnetic focusing of electrons in vacuums, notably in television camera tubes such as vidicons and image orthicons. Electrons take helical paths within the magnetic field. These solenoids, focus coils, surround nearly the whole length of the tube.

Physics:

Infinite continuous solenoid

The magnetic field inside an infinitely long solenoid is homogeneous and its strength neither depends on the distance from the axis nor on the solenoid's cross-sectional area.

This is a derivation of the magnetic flux density around a solenoid that is long enough so that fringe effects can be ignored. In Figure 1, we immediately know that the flux density vector points in the positive z direction inside the solenoid, and in the negative z direction outside the solenoid. We confirm this by applying the right hand grip rule for the field around a wire. If we wrap our right hand around a wire with the thumb pointing in the direction of the current, the curl of the fingers shows how the field behaves. Since we are dealing with a long solenoid, all of the components of the magnetic field not pointing upwards cancel out by symmetry. Outside, a similar cancellation occurs, and the field is only pointing downwards.

Now consider the imaginary loop c that is located inside the solenoid. By Ampère's law, we know that the line integral of B (the magnetic flux density vector) around this loop is zero, since it encloses no electrical currents (it can be also assumed that the circuital electric field passing through the loop is constant under such conditions: a constant or constantly changing current through the solenoid). We have shown above that the field is pointing upwards inside the solenoid, so the horizontal portions of loop c do not contribute anything to the integral. Thus the integral of the up side 1 is equal to the integral of the down side 2. Since we can arbitrarily change the dimensions of the loop and get the same result, the only physical explanation is that the integrands are actually equal, that is, the magnetic field inside the solenoid is radially uniform. Note, though, that nothing prohibits it from varying longitudinally, which in fact, it does.

A similar argument can be applied to the loop a to conclude that the field outside the solenoid is radially uniform or constant. This last result, which holds strictly true only near the center of the solenoid where the field lines are parallel to its length, is important as it shows that the flux density outside is practically zero since the radii of the field outside the solenoid will tend to infinity. An intuitive argument can also be used to show that the flux density outside the solenoid is actually zero. Magnetic field lines only exist as loops, they cannot diverge from or converge to a point like electric field lines can (see Gauss's law for magnetism). The magnetic field lines follow the longitudinal path of the solenoid inside, so they must go in the opposite direction outside of the solenoid so that the lines can form loops. However, the volume outside the solenoid is much greater than the volume inside, so the density of magnetic field lines outside is greatly reduced. Now recall that the field outside is constant. In order for the total number of field lines to be conserved, the field outside must go to zero as the solenoid gets longer. Of course, if the solenoid is constructed as a wire spiral (as often done in practice), then it emanates an outside field the same way as a single wire, due to the current flowing overall down the length of the solenoid.

Finite continuous solenoid

A finite solenoid is a solenoid with finite length. Continuous means that the solenoid is not formed by discrete coils but by a sheet of conductive material.

Irregular solenoids

Within the category of finite solenoids, there are those that are sparsely wound with a single pitch, those that are sparsely wound with varying pitches (varied-pitch solenoid), and those with varying radii for different loops (non-cylindrical solenoids). They are called irregular solenoids. They have found applications in different areas, such as sparsely wound solenoids for wireless power transfer, varied-pitch solenoids for magnetic resonance imaging (MRI), and non-cylindrical solenoids for other medical devices.

The calculation of the intrinsic inductance and capacitance cannot be done using those for the conventional solenoids, i.e. the tightly wound ones. New calculation methods were proposed for the calculation of intrinsic inductance(codes available at ) and capacitance.

Additional Information

A solenoid is a uniformly wound coil of wire in the form of a cylinder having a length much greater than its diameter. Passage of direct electric current through the wire creates a magnetic field that draws a core or plunger, usually of iron, into the solenoid; the motion of the plunger often is used to actuate switches, relays, or other devices.

A solenoid is a coil of insulated or enameled wire wound on a rod-shaped form made of solid iron, solid steel, or powdered iron. Devices of this kind can be used as electromagnets, as inductors in electronic circuits, and as miniature wireless receiving antennas.

André-Marie Ampère was the French scientist, who have invented the calendric coil (i.e. solenoid). Michael Faraday, a British scientist, has created two experiments for the demonstration of electromagnetic rotation. A solenoid engine generally works on the law of electromagnetic attraction.

When an electric current passes through the coil, the solenoid produces a magnetic field and converts that magnetic energy into mechanical motion. Essentially, a solenoid converts electrical energy into mechanical work through electromagnetic forces.

A solenoid’s composition includes a long piece of wire wound into a coil and a moveable plunger (armature) within an iron or steel housing unit. The solenoid works on the principle of “electromagnetism” because when an electric current passes through the coil, it creates a magnetic field inside the coil. Basically, a solenoid converts electrical energy into mechanical work.

What is the Difference Between a Solenoid and an Electromagnet?

Although the solenoid and electromagnet are closely related, they are not precisely the same. A solenoid, or long coiled piece of wire, becomes a type of electromagnet when the purpose is to generate a controlled magnetic field.

However, if the solenoid application impedes changes in the electric current, it can be more specifically classified as an inductor rather than an electromagnet. In sum, a solenoid is an electromagnet - but an electromagnet is not always a solenoid.

What is a Solenoid Used For?

Solenoids are a simple and effective solution for controlling valves, electromagnetic switches, or mechanical interlocks. Solenoid applications are prevalent across numerous industries, including industrial, medical, aerospace, domestic, and automotive.

Solenoids are usually found in applications that require a feature for automatically turning something on or off. Their operation principle and instantaneous response make them a great solution for applications needing a large amount of power in a small space or quick, consistent, and robust operation. For example, many cars’ gearbox drive selector uses a solenoid, which prevents the selection of “drive” without first receiving a release signal from the brake pedal - so starting the car is only possible when parked.

Solenoids also have especially extensive industrial applications where electrical power is required to achieve a movement, such as locking, cutting, clamping, punching, positioning, diverting, holding, or rotating.

Types of Solenoid

There are five basic types of solenoids, and each type’s material, design, and function determine the application. Let’s take a closer look at each type and how they differ in material and design, including examples of applications.

AC- Laminated Solenoid

An AC Laminated Solenoid includes a coil of wire and a metal core constructed with a laminated metal to reduce the stray current, which helps improve the performance of the solenoid. AC solenoids are unique because they deliver a large amount of force in the first stroke, thanks to an inrush current, i.e., an instantaneous high input current drawn by a power supply or electrical equipment when turned on.

AC-Laminated Solenoids are characterized by emitting a clean buzzing sound when they are in operation. They are commonly used with equipment that requires immediate action, such as medical equipment, locks, vehicles, industrial equipment, printers, and household appliances.

DC- C Frame Solenoid

In the DC- C Frame solenoid, the “C” refers to the design of the solenoid frame, which covers the coil and is shaped like the letter C. Although this solenoid is DC configured, it can also be used in equipment design for AC power.

The DC- C Frame solenoid is used in multiple day-to-day applications thanks to its controlled stroke application. Some application examples include gaming machines, camera shutters, scanners, circuit breakers, coin counters, and bill changers.

DC- D Frame Solenoid

The DC- D Frame solenoid includes a two-piece frame covering the coils, forming a rectangular shape, and has a similar function to the C-frame solenoid. The DC- D Frame solenoid has a controlled stroke operation and can be used with DC or AC power.

DC- D Frame solenoids are commonly used with gaming machines, ATMs, and blood/gas analyzers.

Linear Solenoid

The Linear Solenoid is an electromagnetic device that converts electrical energy into a mechanical pushing or pulling force or motion. The linear solenoid’s coil winds around a cylindrical tube with a ferromagnetic actuator or "plunger" that moves or slides "IN" and "OUT" of the coil when electrified.

Linear solenoids are available in two basic configurations: a "Pull-type" that pulls the connected load towards itself when energized, and the "Push-type" that pushes away from itself when energized. The configuration is basically the same, except for the return spring's location and the plunger's design.

Linear solenoids are most common in starting devices, where the switching mechanism helps complete a circuit and allows the current to flow through the mechanism.

Rotary Solenoid

A rotary solenoid has the same elements as the others - a coil and a core. However, the operation is different. The metal core of the rotary solenoid is mounted to a disk with tiny grooves under it, which exactly match the grooves in the body of the solenoid, separated by ball bearings for easy motion.

The rotary solenoid is a unique type of solenoid used for various applications where there is a need for an easy automatic control process. Interestingly, they were originally designed for defense mechanisms; however, today, you can find them in many automated industrial mechanisms like lasers and shutters.

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#1 2025-01-25 16:57:53

Solenoid

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