Bobbin wound coils are one of the most efficient and economical methods of producing coils. As a result, they are frequently utilized in manufacturing, medical equipment, and other systems that generate electricity for residential and commercial establishments.
Two types of plastic materials are used to create bobbin wound coils: thermoplastic and thermoset. Depending on specifications, coils can be insulated with a wide range of materials after being wound on a bobbin. This article will cover the basics of bobbin wound coils and the various tips and techniques for insulating them.
What Is a Bobbin Wound Coil?
A bobbin wound coil is created by wrapping a wire around a bobbin to maintain its structure and rigidity. It facilitates winding arrangement within or onto the magnetic core. Furthermore, the diameters of the bobbin change based on the voltage and current levels, the rating, and the working frequency.
Bobbins are typically hard, pre-formed elements that serve as insulators. As long as a sufficient resistive distance is maintained, they often provide electrical contact between the coil and the connecting core material. They also indicate the features of the coil and the amount of wire utilized.
Techniques for Bobbin Wound Coil Insulation
The bobbin material is typically a component for insulation, allowing it to provide an electrical connection between the coil and the nearby core material. This is generally the case so long as the correct creepage distance is utilized.
There are numerous methods for insulating a coil, including the following:
Potting or Encapsulating
Encapsulation is wrapping electric coils in materials such as silicone rubber, polyester, liquid, or thermoformed epoxy. They provide higher protection against extreme weather conditions, grease, and vibrations than molding.
The main distinction between encapsulated and potted coil techniques is the tooling. Encapsulation uses a reusable mold into which the coil is deposited, filled, and removed after curing. In contrast, the potting process uses a disposable cup, which quickly becomes a finished product component.
Overmolding or Insert Molding
For overmolding or insert molding, a synthetic material is used to cover a coil or assembly. This method maximizes the protection of coiled materials against harsh environmental conditions, such as moisture, oil and grease penetration, salt, and vibration. Moreover, overmolded coils feature dielectric characteristics, consistent diameters, and varied stability.
The overmolding method to insulate bobbin wound coils is often utilized in various industries, including aerospace, electronics, power transmission, and transportation.
Taping or Thread Covering
Taping or thread covering is considered the most cost-efficient technique for insulating coils. It often utilizes readily accessible electrical tapes in various materials, adhesives, and temperature specifications. Although taping may not provide the same degree of protection as other coil insulation methods, it often satisfies the requirements of less severe applications at a cheaper cost.
Vacuum impregnation in transformer coils involves eliminating as much air from the structure as possible and replacing it with epoxy with significantly higher dielectric strength. These epoxies are special adhesives and will link the wires and other components of the construction to create a sturdier assembly.
Commonly, vacuum impregnation is used to enhance the structural integrity of coils, enhance heat transfer, minimize partial discharge, and strengthen environmental protection. It is also used to reduce winding noises.
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Endicott Coil Company has been the leading provider of magnetic components to various original equipment manufacturers for over 65 years! We have gained a reputation for value and performance, enabling us to meet and exceed the needs and expectations of our customers. We also provide services and consulting regarding material selection, test settings, and modifying an existing coil design to reduce costs.
We can design and manufacture any coil, including air core, injection-molded, impregnated, bobbin wound, and sensing coils! Contact us today for additional details about our custom coil services, or request a quote.
An electromagnetic coil, also known as an electric coil is an electrical conductor containing a set of conductive wires wrapped around a specified shape and size. This can be a self-supporting (air core) design or include a customer specified core. Electrical coils are simple electronic components that provide inductance in an electromagnetic circuit. There are many coil types to meet the needs of various equipment. Electromagnetic coils can vary by wire gauge, length, coil diameter, core material, and other factors such as Overmolding.
Overmolding is a multi-step process where two or more components are molded over top of one another. Overmolded coils are protected from moisture, corrosive chemicals, vibration, explosions, and harsh working environments by being molded in a tough temperature resistant material.
In addition to additional insulation and dielectric properties, overmolding can improve:
Grip or “feel”, while providing a stylish appearance that’s attractive to consumers
Reduce shock and vibration
Provide electrical insulation
Improve chemical/UV resistance
Increase product longevity
Definition of an Overmolded Coil
Overmolding requires using a synthetic material to overmold a coil or assembly. This technique optimizes the protection of the winding goods against extreme environmental conditions, such as humidity, oil and grease penetration, salt, and vibration.
A quality overmolded coil has guaranteed and preserved dimensions through precise molds, the proper choice of materials, a consistent manufacturing process, and quality assurance. It is commonly used in various industries, including transportation, aircraft, electronics, and power transmission. Thus, these coils comply with UL, CSA, military specifications, and other applicable standards.
Benefits of Overmolded Coils and Assemblies
Overmolded coils are designed to create components resistant to fluids that would normally compromise the circuit, including solvents,water and oil. This reduces the risk of wire failure in harsh or unstable environments, allowing the completed circuit to continue functioning. Moreover, overmolding of coils enables customer selection of materials with resistance to vibration and other types of degradation based on their specific requirements.
Endicott Coil Company’s Overmolding of Wound-Copper Coils for the Electronic Industry
Endicott Coil Company manufactures epoxy molded, wound copper coils for the electronic industry. Depending on the requested coil dimensions, we utilize high-quality presses and carefully selected epoxy compounds, including Farboset, BMC, MH6, and Rynite .
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Since 1954, Endicott Coil Company has been the #1 supplier of magnetic components to various original equipment manufacturers! We have a solid track record for performance and growth, allowing us to meet and exceed the requirements and expectations of our customers.
Our engineering staff is exceptionally competent and offers expertise in electric coil winding assembly customization. We can accommodate various coil requirements based on our customers needs, including self-supported, injection molded, bobbin wound, impregnated, and solenoid.
Contact us today to learn more about our coil services! You can also request a quote to collaborate with us on your next project.
An electric coil comprises two distinct components: a conductor and a core. The conductor is typically made of solid copper wire wrapped around a metal core. A turn is created each time the wire is looped around the core, while multiple turns are considered a coil. It acts as an electrical conductor, efficiently sending an electrical current to generators, electric motors, electromagnets, and inductors.
The most common application of an electric coil is as an inductor, which stores energy within its electric field. As a passive electronic component, an inductor has no gain and thus cannot control the directional flow of energy. Instead, it captures energy from the electric current flowing through its body.
Electrical coils are typically required in industrial manufacturing, medical equipment, and devices used to supply electricity to commercial and residential buildings.
Definition of an Encapsulated or Potted Coil
Like any other electrical coil, an encapsulated or potted coil is constructed from a ferromagnetic metal wire wrapped into a specific diameter. It is an electromagnet that is only activated by magnetism when exposed to electric currents. Since most coils use outer casings for protection from harsh environmental conditions — such as salt, water, moisture, and vibration — encapsulated coils are frequently molded into liquid or thermoformed epoxies. This procedure causes the coil to fuse with its casing.
Both encapsulated and potted coils surround and seal the coil with liquid materials, including silicone rubber, epoxies, and polyesters. These materials are available in temperatures ranging from 105 °C to 190 °C. The only difference between the processes for encapsulated and potted coils is the tooling: encapsulation utilizes a reusable mold into which the coil is placed, filled with material, and then removed after curing. Meanwhile, potting uses a single-use cup, which soon becomes a component of the final product.
Advantages of Using Encapsulated or Potted Coils
Encapsulated or potted coils have high dielectric and isolation properties and uniform dimensional and cosmetic characteristics. Thus, they often provide better protection against extreme environmental conditions than molded coils. Besides that, because they are dipped and thermoformed into sealing liquid, epoxies such as silicone rubber provide vibration protection that molded casings do not. Encapsulated coils can also be heat-treated after manufacturing, which sinters the plastic component with the molded coil inside, providing excellent protection.
Moreover, encapsulation and potting processes aid in transferring heat and protect the components from thermal shock and adverse working environments, such as grease, salt, water, humidity, and gasoline. Finally, they provide a cost-effective alternative to overmolding when a protective outer shell is required, as overmolding tooling can be costly and impractical in small volumes.
Endicott Coil Company creates customized encapsulated coils resistant to the harshest environmental circumstances. Depending on the customer’s application, our experts select the best encapsulation material, such as thermoplastics, thermosets, epoxies, silicone rubber, and polyesters.
We are fully equipped with vacuum chambers, vacuum ovens, and curing ovens to achieve a proper cure regardless of the material used.
Our company produces encapsulated coils with temperatures ranging from 105 °C to 240 °C. To ensure that all specifications are met, these coils are extensively tested using hi-pot, inductance, resistance, leak, and surge testing.
High-Quality Custom Coils and Components From Endicott Coil Company
Endicott Coil Company, Inc. has a long history of providing high-quality custom magnetic components and services. Our company leverages our extensive knowledge, expertise, versatility, and capabilities to meet and fulfill each customer’s specifications. We also offer comprehensive value-added services — such as overmolding, encapsulation, and sub-assembly manufacturing — in addition to our wide assortment of coils and transformers.
Our facility is RoHS compliant and employs ISO methodologies and procedures throughout the manufacturing process. Furthermore, we have experience with ASTM, CSA, VDE, NRC, Mil-Spec, and UL testing procedures.
Contact us today to learn more about the products and services Endicott Coil Company offers. You can also request a quote now!
An electric coil, also known as an electromagnetic coil, is an electrical conductor composed of wires wrapped around a cylindrical, disk-shaped, or toroidal ferromagnetic core. It is one of the most basic electronic components, providing inductance in an electric circuit. Inductance refers to an electrical property that opposes current flow through the circuit.
Electric coils are widely used in applications where electric currents interact with magnetic fields. These include the manufacturing, engineering, and medical industries. They are also found in devices and equipment such as electric motors, generators, transformers, inductors, and sensor coils.
Definition of a Self-Supported Coil
Self-supported or air core coils are created by coating magnet wire with an adhesive and then wrapping it in an insulating film. Solvents, hot-air heating, and post-baking can all be used to activate the adhesive and secure the adjacent strands of magnet wire. They are also wound on collapsible mandrels, allowing disassembly without damaging the wire insulation. The mandrels can be machined into nearly any shape to accommodate any desired coil configuration.
These coils are ideal for electronic applications where a bobbin or other coil form is impossible due to dimensional constraints. They reduce bobbin costs while increasing copper content in a given area.
Presently, bondable magnet wire with fundamental solutions up to 180° is available. However, the strand-to-strand bond typically begins to soften at temperatures 10° to 15° below the insulation rating. A bondable wire is also useful when magnet wire bonding is preferred to prevent movement or wire abrasion in applications where other processes, such as impregnation or varnishing, are not recommended.
Advantages of Self-Supported Coils
One of the most significant benefits of a self-supported coil is the low signal loss that occurs at higher magnetic field strengths. Ferromagnetic cores such as iron can become magnetically saturated when the magnetic field is too strong, causing an inductance loss. This is not a problem for self-supported coils as they can carry electromagnetic frequencies up to 1 GHz. Conversely, ferromagnetic core inductors lose efficiency once the frequency exceeds 100 MHz.
Self-supported coils are also simple to build since they are unaffected by the value of the electric current they transport. If there is no ferromagnetic core, they are more suitable for low-power devices, such as commodity electronic products, computer devices, communication equipment, and other consumer goods.
CNC Winding of a Self-Supported Copper Coil by Endicott Coil
Endicott Coil Company, Inc. manufactures a wide range of self-supported coil shapes and sizes for use in various space-constrained electronic applications. Based on customer specifications, the company uses CNC equipment to wind strands of coated 24-48 AWG copper magnet wire to the desired shape. The bondable coating is then activated via a solvent or heat cure to secure the magnet wire strand-to-strand.
Endicott also solders and trims the finished pieces using in-process gauging to maintain tolerances of less than 0.005 in.
Partner With Endicott Coil Company for High-Quality Custom Coils and Components
Endicott Coil Company, Inc. has been the leading supplier of magnetic components to a wide range of OEMs for over 65 years! We have earned a solid reputation for value and performance, enabling us to meet and exceed our customer’s needs and expectations.
Our company can significantly help with material selection, parameter testing, and cost-cutting redesigns of existing coil designs. Endicott Coil’s engineering team is also exceptionally skilled and specializes in custom electric coil winding assemblies! We can create and construct any coil type, including self-supported, injection molded, bobbin wound, impregnated, and sensing coils.
For more information on our coil services, contact us right away. You can also request a quote to start your next project with Endicott Coil Company!
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An electric coil is a fundamental type of electronic component which provides inductance in a circuit. In other words, it is an electrical feature that opposes current flow. These coils are classified according to the coil diameter, wire gauges, number of turns and core materials.
Electric coils are commonly used in manufacturing, medical instruments, and other devices that generate electricity for homes and businesses. They are meticulously designed according to their intended applications. Various electric coils are made up of a core and wiring wrapped around it; one of these is the bobbin wound coil.
Definition Of A Bobbin Wound Coil
Bobbin wound coils are created by wrapping a wire around a bobbin to keep its shape and rigidity. It makes winding assembly into or onto the magnetic core easier. The bobbin diameter varies with voltage and current levels, rating, and operating frequency.
Bobbins are rigid, pre-formed components that typically act as insulators. As long as an adequate resistive distance is used, they provide an electrical connection between the coil and the connecting core material. They also specify the coil’s characteristics and the amount of wire used. Moreover, they aid in determining the coil’s temperature rating, the device’s dielectric properties, and other coil-related features.
Most bobbins are molded, while others are fabricated. Designs for these frequently include terminals, pins, and surface mount pads for wire termination and printed circuit board mounting.
Considerations When Designing A Bobbin Wound Coil
Bobbin wound coils are the most efficient and cost-effective method of producing coils. However, it is critical to choose the most suitable bobbin to achieve the best bobbin and wire combination. The following are some of the most important factors to consider:
A critical material consideration is the amount of heat a plastic molded bobbin must withstand; it should be strong enough to endure soldering temperatures for a short period during production. Two types of plastics are used in bobbin molding: thermoplastic and thermoset.
Thermoplastic materials are the most commonly used in bobbin molding. When mixed with mineral, quartz, or glass fillers, thermoplastic bobbins are economical and can satisfy many heat and flammability requirements. However, these materials are more costly. Still, they provide the highest strength and temperature performance.
Although DAP and epoxy plastics are suitable for toroid mounts and potting cups, their brittleness makes them unsuitable for bobbin applications. On the other hand, phenolic plastic is ideal as a bobbin because it is stable at high temperatures.
Cost And Shape
The square stack lamination sizes E187, E24/25, E375, E21, and E42/15 have the cheapest core and bobbin combination with the greatest availability. However, such leg shapes may need to be protected with copper foil to reduce electromagnetic interference (EMI), increasing the cost.
You can also consider the newer round center leg cores and bobbin combinations. Common examples of this core style include ETDs, PQs, EFDs, and EPs made of ferrite. These recent combinations are more expensive than the square ones, but they are easier to wind and provide good EMI shielding.
Orientation Of The Bobbin And Core
Vertical mount bobbins require less board space but are taller than horizontal mount bobbins. Wire termination is also more complex, and only a few multi-section types are available.
On the flip side, horizontal mount bobbins are less visible but take up more board space. These types also make wire termination easier, and many multi-section types are available.
The requirements of the safety agencies apply to the entire process of inductor construction. These regulations address insulation and spacing to prevent thermal aging and an electrical malfunction in the winding from developing over time.
UL 1446 is the primary specification in the United States that controls the insulation requirements of these products. This standard covers motor, transformer, and coil insulation. Meanwhile, UL 510 is another essential regulation for the flammability of electronic tape, frequently used in the design of a transformer or inductor.
Tips For Insulating Bobbin Wound Coil
Coils can be insulated with various materials after being wound on a bobbin to meet your specifications. Some methods for insulating a coil are as follows:
Tape or Thread Covered
The most cost-effective method of coil insulation is to use one of the many electrical tapes on the market. These tapes are widely available and come in various materials, adhesives, and temperature ratings. Despite not providing the same level of protection as other options, tapes frequently fulfill the requirements of less stringent applications at a lower cost.
Impregnation can provide many benefits of molded and encapsulated parts without the expense of dedicated tooling. Impregnants form a bond between the wire and the filler, improving heat dissipation. You can also improve the dielectric properties by selecting the right impregnated coils.
Encapsulation or Potting
Encapsulation involves enclosing the electric coils in silicone rubber, polyester, liquid, or thermoformed epoxy casing. They provide better protection from harsh weather, oil, and vibration than molded coils because they are frequently dipped or thermoformed into sealing liquid epoxies.
In overmolding or insert molding, a coil is overmolded using a synthetic material in a subsequent process step. This method protects the winding materials from harsh environmental conditions.
Endicott Coil Company For High-Quality Custom Coils And Transformers
For over 65 years, Endicott Coil Company, Inc. has been the top supplier of magnetic components to a wide range of OEMs. We have built a reputation for service and quality, allowing us to meet and surpass our customer’s needs and requirements.
We have a highly skilled engineering team that specializes in custom electric coil winding assemblies. Our expertise and versatility allow us to design and build any coil type, including air core, injection molded, impregnated, bobbin wound, and sensing coils. Endicott Coil Company, Inc. can also help with material selection, test parameters, and redesigning an existing coil design to save money.
Contact us now for more information on our custom coil services. You can also request a quote and let us make your innovative ideas a reality!