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 Impregnating
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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