What is a Solenoid Coil?
A solenoid coil is a common electric device that consists of a wire wrapped around a core, normally made out of metal, for electromagnetic capabilities. When electrical current flows through the coil, an electromagnetic field generates the force that creates linear motion. Solenoid coils are one of the simplest types of linear actuation devices.
How Solenoid Coils are Used?
Solenoid coils are extremely flexible electromagnetic devices that are essential for a wide range of applications and industries, from factory automation to consumer electronics.
As the key component of solenoid actuators, the primary purpose of solenoid coils is to have automatic switching, locking, or movement of components inside electrical circuits or mechanical systems.
When electrical current is applied to the solenoid coil, it produces a magnetic field that magnetizes a movable armature, which in turn engages and operates connected devices or mechanisms.
Solenoid coils are commonly used in a wide range of automated applications and electromechanical systems because they are reliable, capable of fast response times, and their installation is simple and effective.
In industrial environments, solenoid coils are often used alone or in pairs to operate hydraulic and pneumatic valves, industrial robots, dedicated and automated gate systems, and machinery that requires precision on-off or direction control of process control.
Solenoid coils are also frequently the basis of safety interlocks, high-speed sorting machines, as well as any electrical machine or process control requiring the conversion of an electrical signal into mechanical actuation.
How Solenoid Coils are Used
Locking Mechanisms
Solenoid coils are a major technology employed in automatic locking systems (for instance, door locks typically used to secure high-security facilities or restricted access areas) where the solenoid coil is in a non-charged condition when locked, then becomes charged when powered and retracts the locking bolt allowing access.
A fail-safe manner in access control systems, safe deposit boxes and any smart security solution requiring remote or automated actuation is essential.
Medical Applications
In an increasingly challenging and competitive environment solenoid coils are widely utilized in the medical device industry where high reliability, electromagnetic compatibility and precise actuation are all mission critical.
In dialysis systems, solenoid coils activate miniature valves to control blood and fluid flows. In automated medication dispensing systems solenoid coils provide precise dosing by opening or closing delivery channels/valves when required.
Solenoid coils are commonly found in a wide range of medical devices including, but not limited to, medication delivery infusion pumps, oxygen machines, diagnostic imaging machines, respiratory devices, anesthesia machines, gas chromatograph equipment, etc.
Due to the complexities and difficulties concerning medical regulations for manufacturers, solenoid coils for medical devices are manufactured using sophisticated materials and quality control processes so that they have high isolation resistance, low power consumption and fail-safe aspects for continual duty cycles.
Automotive
In the automotive sector, solenoid coils (or solenoids) have become essential components for reliable and rapid switching capabilities as the advent of automated vehicles and electronic control systems have increased.
In automotive applications, solenoid coils are used to enable transmission shifters, control starter motors, open fuel injectors, function anti-lock braking systems (ABS), and function emissions control devices.
Solenoid coils in today’s vehicles control automatic transmission gear selection, automatic air conditioning systems, enable keyless entry systems and immobilizers, and turn on entertainment or infotainment.
The precise and high-speed actuation of solenoid coils provides a direct contribution to vehicle safety, performance, and increased driver comfort.
Irrigation System
Solenoid coils are essential linear actuator devices in both landscape management and agricultural irrigation applications and are integrated into on-off water valves.
The irrigation solenoid valves allow an irrigation controller or smart timer to control or turn on/off an individual water flow, maximizing the efficiency of water usage, and allowing for automated irrigation scheduling and systems.
Irrigation solenoid valve coils are designed for life outdoors; they are weatherproof, submersible, and compatible with multiple plumbing standards. While designed to last and be used outdoors, solenoid valve coils are susceptible to clogs.
Clogs may consist of sediment or debris and can cause pointing to the solenoid valve to stick either open or close, water may escape or irrigation will be insufficient as a consequence.
Most clogs can be avoided with appropriate filtration and maintenance, both issues can generally be avoided, and the life of a system can be extended.
Aviation
Solenoid coils are an honorable technology in aerospace, providing dependable captive power management, as well as protection of sensitive avionics.
An aircraft uses solenoid relays or contactors to physically separate sensitive avionics from the circuit voltage transient spikes caused by an engine startup.
Aviation solenoid coils are designed and tested to rigorous industry standards for vibration resistance, EMI shielding and high-cycle duty.
Solenoid coils can help protect flight-critical electronics and communications systems, as well as provide safe stations for stable aircraft operation, by correctly switching the connection between the avionics bus and the master power bus.
Hydraulic Solenoid
Hydraulic solenoid coils are essential parts of hydraulic solenoid valves. These valves constrain and regulate the movement and direction of hydraulic fluids in a variety of machines.
Hydraulic solenoid coils and valves enable operators to control the flow of hydraulically charged liquids remotely by energizing the coils to open or close valves. Once opened or closed, valves allow the pressure flow of liquid either to actuate components (i.e., hydraulic cylinders, actuators, and motors) or to remove and stop the pressurized flow.
Hydraulic solenoid coils are commonplace in industrial automation applications, construction equipment, motor vehicles, injection molding, and other heavy equipment applications, any time pressurized flow-controlled components need to be controlled where there is little tolerance for error or lots of pressure.
When considering solenoid coils, some of the major specifications include, electrical voltage with rated voltage tolerances, insulation class (temperature ranges), power consumption, coil response time (how long it take the coil to deactivate and/or activate the valve), and the duty cycle (time in operation).
These aspects of hydraulic solenoid coils ultimately help match a coil for proper efficiency and safety against project expectations.
Pneumatic System
Pneumatic solenoid coils are coils that are actuated electromagnetically; they activate valves either in systems employing compressed air or gas. Once the coils are energized, the pneumatic solenoid opens or closes the pneumatic solenoid valves.
This allows or restricts the flow path to the various pneumatic actuators or cylinders or other pneumatic devices.
Pneumatic Control systems utilize two-way, three-way, or five-way pneumatic solenoid valve designs to create bi-directional or multi-position control, to support mechanical interfaces for high speed automation and packaging, conveyors, and air tools.
In more advanced systems, a pneumatic solenoid valve can use a double coil to independently and selectively operate the individual flow paths to add further flexibility to the industrial automation solution.
Many of these electromagnetic coils have rapid switching / high reliability with toleration of varying temperatures and pressures encountered being used in pneumatic circuits. The basic features to specify, were voltage, coil resistance, and compatibility with a valve manifold system.
Pinball Machines
In the realm of recreational technology, pinball machines use solenoid coils. Solenoid coils offer quick, high-speed actuation to launch the ball with bumpers, propel the ball with flipper arms, etc.
A solenoid coil delivers kinetic energy by retracting a metal plunger quickly and then releasing it several times quickly.
In current manufacturing approaches, modern pinball mechanisms use high-quality solenoid coil assemblies to improve operator engagement, while also utilizing design features to enhance safety using pulse-width modulation, heat resistance, etc., to protect the coil and control overheating in continuous-motion play…and ensure reliable service life.
Retaining proper timing on coil use during play is crucial for consistent performance, avoiding mechanical wear and tear.
Choosing the Right Solenoid Coil for Your Application
The right solenoid coil is dependent on specific application variables including the voltage requirements (AC or DC), the coils resistance, insulation class, response time, duty cycle, and compatibility with the controlled device.
It is just as important to consider the environmental aspects such as the temperature range, moisture exposure, chemical exposure, and duty environment (continuous duty or contained duty).
Most solenoid coil manufacturers have options for custom specifications and off-the-shelf coils made for different markets including automotive, industrial automation, fluid handling, and medical.
When considering solenoid coils, it is a great idea to check the engineering datatsheets and utilize supplier engineering support to provide the best solution in performance, life and safety for your automated project.
Whether you want to view a large selection of high quality solenoid coils or any electromagnetic actuator, reach out to an experienced suppliers and you can be assured of reliable, efficient solutions designed for your application, whether it be for industrial, commercial, or specialty equipment.
How Solenoid Coils are Made?
A solenoid coil is constructed when wire, most frequently copper or aluminum wire, is wound around a hollow core forming a cylindrical coil.
The construction of the solenoid coil is a key factor developing a strong electromagnetic field used in electromechanical devices. Industrial applications include, but are not limited, to: industrial automation, pneumatic actuators and hydraulic valves.
Solenoid coils are constructed to operate with either direct current (DC) or alternating current (AC). Coil voltage can include: 6, 12, 24, 120 and 220 volts, ensuring the coil used is compatible with a broad range of available circuit design and control systems.
Low voltage and therefore safe option for coils are those defined as 24 volts or less, most commonly used in sensitive electronic circuits or for small machines. This voltage has the greatest ability to safely provide sufficient solenoid actuation without danger.
An amplified voltage would apply to high voltage solenoids operating above 24 volts. High voltage can commonly be found in heavy-duty industrial applications, automation or electromechanical actuators with high demand conditions.
The two basic types are tape-wrapped and encapsulated solenoid coils. Tape-wrapped solenoid coils tend to be applied in less demanding applications, such as clocks, timers, industrial pneumatic solenoid valves and general electronic devices, where solvents, moisture and aggressive chemicals are minimal.
Tape-wrapped solenoids are designed to achieve reliability and quick assembly, and are developed/ manufactured at lower cost in a more appropriately controlled environment.
Encapsulated solenoid coils have outer layers of protection made from polyester, rubber or epoxy resin. Encapsulation will provide insulation resistance, high dielectric strengths and a higher mechanical quality/durability.
Encapsulation is a critical performing scenario to achieve an acceptable performance level in a demanding industrial scenario.
Hidden by the encapsulation, solenoid coils are more appropriate for outdoor automation systems, hydraulic valve actuation or a machine subject to vibration and contaminants.
Encapsulation is also the preferred build style of coiled solenoids operated by electricity on safety critical solenoid operated various forms of valves, due to enhanced long-term performance, protection from environmental type exposure.
How Solenoid Coils are Made
Copper Wire
Copper wire, an outstanding wire choice for solenoid coil manufacture, is selected for its high electrical conductivity, thermal stability and easiness to use for winding.
Collectively through these characteristics, the wire is a superior choice for transferring power efficiently and producing electromagnetic force.
While other wire may be possible, such as aluminum, copper tops the list of materials used for manufacture in high-performance solenoid actuator coils and electromagnetic relays.
The copper wire classes that are best suited to solenoid coils are F, H, and N. F, H and N are made due to their resistance to heat (Highest, High, Normal). These insulation type wires work well for demanding industrial control applications.
The diameter of the wire is critical to the coil’s resistance, inductance, and current carrying capacity. If the wire is to thin, it will lower the electrical resistance and increase heat dissipating, possibly leading to coil failure due to overheating.
This is especially true in applications where the solenoid is continuously operated or where the solenoid is operated at a high frequency.
Correct wire gauge selection is fundamental when considering the manufacture of high quality miniature solenoid assemblies and using inductive loads for powerful industrial electromagnetic actuators.
Class F
Class F copper winding is rated for use at temperatures of more than 155°C. There is operational stability at an ambient temperature of 20°C and media temperatures of 100°C. This makes them practical for standard industrial automation and control circuit roles.
Class H
Positions and Class H expansion windings are reliable in ambient temperatures up to 50 degrees Celsius; however, media temperatures can be as high as 180 degrees Celsius.
Class H copper windings provide protection at high operating temperatures relative to Class F and Class B copper windings.
Class H windings can be used in heavy-duty power solenoids and electric actuator coils that operate under high demands which are typical in industrial applications.
Class N
Class N Windings are considered thermally stable when the rated temperature is greater than 200°C. These windings are rated to operate in ambient temperatures of 80°C and 200°C media temperature, which allows advanced deployment applications with Class N windings to promote applications where optimum performance is essential for electromagnetic switching or quickly actuated high-efficiency solenoid valves or energy-demanding industrial machines.
Coil Bobbin
The bobbin serves a stable support and a shape for the coil winding. It keeps the wire in the proper placement and protects the physical structure of the solenoid coil.
It maintains the lead wires, helping to prevent mechanical stress on the lead wires and helps in making sure the components inside the solenoid are in an accurate orientation, which can affect the actuator response and stroke consistency.
Use durable materials for the bobbins, such as high-temperature engineered plastics, engineering materials with composites, low-friction materials, electrical, electrical insulated materials, and capable of enduring repetitive cycles of automation.
Assemble connectors, such as DIN connectors into the bobbin design further standardized installation and was able to provide electrical connectivity with control panels and more complicated valve assemblies.
Winding
The number of turns of wire is based on the requirements of the solenoid coil performance specifications, e.g., how much inductance is required; how strong of a magnetic field is needed; how much current is the coil designed to handle; etc.
More wires wound closer together creates a stronger electromagnetic field, making them suitable for high speed actuation, power relays, or magnetic latching.
Because the solenoid coil is made of windings or turns of wire, the way winding and core parameters such as the resistance of each coil turn (ohms per unit length), bobbin diameter, and the method of winding (single layer or multiple layers), all affect the ability of the solenoids to respond quickly and the energy efficiency of inductive devices used in industrial power control.
An increase in number of turns increases the density of the magnetic flux and affects the force output and the precision of solenoid valves, electronic and wether proof/redundant automation switches, or relay modules.
The number of turns can be determined based on conductor size and thermal quality to ensure that the solenoid will be operated safely and dependably form a wide range of industrial and automotive solenoid coil applications.
Coil Core
The core material internal to the solenoid coil is significant in optimizing the magnetic field produced by the winding.
The benefit of using cores is that they typically consist of a ferromagnetic metal, which enhances the electromagnetic strength, and is especially important in solenoids for linear actuators, hydraulic solenoid valves, and almost every servo actuator.
Some solenoid coils incorporate air cores, particularly for high frequency circuits or where low inductance is present, though using solid metal cores, in this case soft iron or composite alloys, can increase magnetic field strength as much as 100 times more than air core models, providing stronger actuation forces and an overall more efficient methodology for actuation purposes.
Air core solenoids (glass or plastic) are preferable for high frequency circuits such as RF transmitters because they have less eddy current losses and operate at high frequencies to one gigahertz (GHz) spectrum.
Also, metal core-solenoids, such as those with laminated iron around the coil or special ferromagnetic alloys, can operate effectively to 100 megahertz (MHz) and provide robust and reliable power in actuation or performing specific tasks in automation systems and electromechanical relay applications.
The primary solenoid core types include:
- Alloy Iron – High permeability and saturation magnetic strength, used in heavy-duty solenoid actuators.
- Electrical Pure Iron – Low eddy current losses and uniformity for control solenoids.
- Ferronickel – Improved magnetic properties for precision automation applications of solenoids.
- Ferro-Aluminum – Lightweight design, makes it ideal for low hysteresis and responsive solenoid designs.
- Ferro Cobalt – Provides maximum saturation magnetic strength for very fast and powerful actuation.
Solenoid Coil Protection
The protection of solenoid coils from adverse effects for reliability and electrical safety during the lifespan of the coils is essential. Two ways to protect solenoid coils are wrapping and encapsulating. Each has specific environmental use and application.
The choice of protection can either be tape-wrapped for standard industrial controls or fully encapsulated for Class 1 Div 1 rated in hazardous areas, and will have considerably greater longevity in a challenging environment for coil life in automation applications and fluid power systems.
Wrapped
Wrap-type solenoid coils utilize layers of insulation tape or paper for easy and low-cost physical protection. This technique adequately protects for the use of coils in non-corrosive locations, and in a controlled environment.
It provides adequate amounts of insulation to prevent short circuits assuring functionality when used in light duty applications like circuitry, simple actuators, and basic electromagnetic relays.
Encapsulated
Encapsulated solenoid coils are protected by robust materials, such as epoxy, rubber, specially formulated polyester resins, and engineering plastics that encapsulated coils can resist abrasion, moisture, chemicals, and voltage spikes, making them highly advantageous across oil and gas, process automation, outdoor powered equipment, and safety-critical systems.
Encapsulation improves a solenoid coil’s capability to deal with industrial contaminants, extreme vibration, and electrical spikes.
DIN Connectors
DIN connectors are intended to provide a standard way of electrical connectivity to solenoid coils, especially regarding modular automation and cabinet configurations as proposed by Deutsches Institut für Normung.
Presently, replacing lead wires in this manner provides an easy-to-use, secure, quick disconnect interface to allow ease of installation and removal, and maintenance and replacement of coils in both solenoid valves located in the non-traditional field and in factory automation systems where the interchangeability among coils is often highly desirable.
DIN connectors are mostly used with encapsulated solenoid coils, but can be provided as part of some bobbin type housing designs if the coil design allows for development.
Providing connectivity allows troubleshooting, upgrades and maintaning production to be minimized since higher levels of standardization exists for industrial applications and environments related to PLC interface modules and industrial machines requiring fast coil exchanges.
How a Solenoid Coil Works?
The major function of a solenoid coil is to convert electrical energy to mechanical energy, producing linear motion. A solenoid coil is made up of a wire wrapped around a piston made from ferromagnetic material.
A solenoid coil differs from a permanent magnet, in that it can be turned off and multiples it can be used in electrical switches, valves, and actuators to quickly make automatic applications.
Like all magnets, a solenoid coil has positive and negative poles that will attract or repel ferromagnetic or non-ferromagnetic material dependent on the polarity of the components.
The magnetic field produced by the solenoid moves the core or piston forward or backward, producing the forward or backward motion required to engage or disengage a timely manner.
How a Solenoid Coil Works
A solenoid coil functions similarly to magnets by controlling electrical energy to produce mechanical movement, which generates linear movement. A solenoid coil then consists of wire that is wound around a ferromagnetic material piston.
A solenoid coil can be turned on and off, that is where a magnet cannot, therefore a solenoid is used in switches, valves and a host or other automatic devices.
Just like a magnet you have positive and negative poles, which can attract and repel various materials based on their magnetic sensitivity.
The impressive fact is that the solenoids generate a magnetic field which will drive the core of the piston to any position you may want thus allowing you to potentially run or stop potentially a variety of applications.
The solenoid coil has two main parts, the electrical input and field that it generates. Since for example, you may use a magnet to move a metal object in a different positions or directions, it is still a magnet. The solenoid can control the field supplied by electrical activation for exact location control.
Every wire when electric current is flowing through it has an extremely weak magnetic field. When you coil those wires with a solenoid, you amplify/strengthen that extremely weak magnetic field. Each time you coil the wire, you strengthen the magnetic field, and now you have created something much larger than a straight wire.
As with all electrical gadgets they must have a closed circuit connection between the power supply and into the device. A switch provides a solid method to break the closed circuit.
If the demand for power increases, then the size of the switch size must also increase., good news it takes very little energy to activate the switch. Solenoids are great at doing this; hence a 24-volt solenoid activating and deactivating a 240-volt machine.
If you were to use a heavy duty switch for this heavy duty application and large piece of equipment, everything theoretically would work, however it might take an awful lot of wire and power, and control may be an hour longer.
Solenoids will require less power to operate than use so in theory, the offer control because the wire can be increased to reduce the cost when power is on.
The solenoid coil movement will either turn on or off the application when activated. So we can see a simple application allows you to control very large applications, with exceptionable energy consumption.
Different designs of mechanical solenoid coils can provide different implications. For example, a solenoid can stay engaged in the locked position of a door lock mechanism. When you apply electric current to the solenoid, the plunger retracts and the unlock allows the door to open.
Proportional solenoid coils are especially useful features of the solenoid as they convert electric signal energy into a proportional mechanical force.
Like a proportional solenoid will move at various positions from an electric current, while producing different amounts of force. Proportional coils are went even further with regards to use valve openings and usually have actuation of plunger to control flow rates.
What are the Types of Solenoid Coils?
There is an array of solenoid coils that can be used for just about any type of application conceivable. Solenoid coils vary in design, materials used, and intended use.
Even though there are a range of solenoid coils and very specific applications for the coils, all solenoid coils operate under the same principles based on electricity.
Solenoid coils are also commonly considered as solenoid valve coils for fluid control. Also, solenoid coils, are commonly considered in automation, for machine controls and robotic applications.
Solenoid coils are typically considered as either wrapped or cast, and are also categorized based on power sources; alternating current (AC), or direct current (DC).
The decision to consider either AC or DC, for these coils should be determined based on several parameters in relation to the coil application.
Solenoid Coils Types
AC Laminated Solenoid Coil
An AC solenoid coil can exert a tremendous amount of force on the first stroke due to the amount of current flowing into it when engaged. Because of this, the coil can generally perform several strokes.
AC laminated solenoid coils come in several designs and produce a buzzing sound when actuated. The AC solenoid coil is excellent for applications that require a quick response, such as in instruments, automotive, printers, and appliances.
DC C Frame Solenoid Coil
The DC solenoid C frame has an open frame design to allow linear motion. It is one of the simplest and most economical ways of constructing a solenoid, while also being extremely high-performing.
The solenoid is available as a push configuration or pull configuration and is frequently utilized in simple applications such as in circuit breakers, scanners, coin counting devices, and point-of-sale devices.
Linear Solenoid Coil
A linear solenoid coil, which is also commonly referred to as a linear electromechanical actuator (LEMA), can be used in either a continuous operation mode or an on/off mode.
LEMAs can be made as proportional solenoid coils, in which the plunger would be positioned along the plunger’s stroke according to the power input. The term “linear solenoid coil” refers specifically to the linear motion of the plunger when the coil is energized.
Rotary Solenoid Coil
Linear devices that either oscillate back and forth in linearly, are solenoid coils. Rotary solenoid coils convert linear motion into rotary motion with three ball bearings. When the rotary solenoid coil is energized, the armature is then drawn towards the stator and will rotate along an arc.
All coils produce angular or rotary motion and may do so in clockwise, counterclockwise, or bidirectional motion.
The rotary motion of the rotary solenoid coil may be 25°, 35°, 45°, 60°, or 90° and may even involve several movements of a specified angle. The rotary motion may be produced when either energized, de-energized, or if the electromagnetic field changes polarity.
DC – D Frame Solenoid Coil
A DC D frame solenoid coil is housed in a two sided D frame design. This design gives slightly increased force output and better environmental performance.
D frame solenoid coils have a low cost configuration ideal for high volume applications and continuous duty. They are obtainable for on and off operation.
With the different size and stroke options of DC D frame solenoids, they can consistently perform for millions of cycles.
Solenoid Valve Coil
A solenoid valve coil serves the purpose of controlling the flow of liquids and gases in pipe, duct and tube systems. There are different solenoid valve coils for the different needs for fluid flow applications.
Direct Acting
Direct acting solenoid valve coils have a plunger that closes a small orifice without additional force. Direct acting solenoid valve coils are very fast acting, have the capability to work under pressure, and are available in either a normally open or a normally closed coil.
Pilot Operated
The solenoid valve coil is a “pilot operated” or “indirect acting” type of coil that uses pressure from across the port of the valve to open or close the valve. It is energized to open the valve while the pressure from the system holds the valve closed.
Two Way
A two-way solenoid valve coil consists of two ports that can open or close to control fluid flow as desired. Two-way solenoid valves are typically found wherever the control of a release or restricting flow of fluids is required, like in air compressors, etc.
Three Way
A three-way solenoid coil has three ports and two openings alternating according to the coil. Two of the ports are inlets and the last is an outlet. This setup provides the functionality of controlling two different fluids.
Four Way
A coil on a four-way solenoid valve provides an extra port, where two of the ports are inlets and the two ports are outlets. This is designed to operate double-acting solenoid valve actuators.
Conclusion
- A solenoid coil is a standard electrical device designed with a wire that is wound in close refresh around a core, commonly made of metal, which develops an electromagnetic field.
- The electromagnetic field created in the core of a solenoid coil is used to pull an armature that will work against the spring tension of the core, which offers linear motion in order to activate a switch, ring a doorbell, or to turn on a paintball gun.
- Solenoid coils are a really versatile device and its a component of production machines, toys and appliances, etc. It can be found in many different forms of automation.
- A solenoid coil has wires (copper or aluminum) that has been wound around a hollow geometric form.
- The function of the solenoids coils is to change electrical energy to mechanical energy to create linear motion.