Is insulation necessary for a coil?

The importance of insulation in electrical systems can’t be overemphasized. It protects you from electrical shocks. You may wonder if the same applies to electromagnetic coils. So, is insulation necessary for a coil?

It’s necessary to insulate coils. Without insulation, there’s a risk of explosion, and the coil will most likely not work. Several devices use coils, including transformers. These voltage control devices use materials such as mineral oil, Askeral, Nitrogen and air, and Fluorogas for insulation.

However, it’s not only coils that require insulation. You can also insulate regular electrical wires if the plastic covering peels off. Here, we discuss why insulating a coil is necessary.

What is a Coil?

A coil is an electronic circuit of current-carrying wires that produce a magnetic field or electrical inductance. Coils are usually circular or cylindrical. They are necessary for rotating devices and any device that requires electric current to interact with magnetic fields. 

You’ll find coils in transformers, electric motors, inductors, generators, and electromagnets. Due to their shape, coils increase the strength of the magnetic field produced by a current. Several home appliances use a coil, such as electric fans, heaters, cloth dryers, etc.

Insulation is crucial for coils. This prevents short circuits in coils by allowing the current to go the right way and complete the turns necessary to generate the electromagnetic energy. The right way is for the current to go around the coil. Without insulation, the current will follow the path with the least resistance across the wire. Lack of insulation can lead to the explosion of the transformer.

The insulation of the coil starts from the wires used for winding. Enamel wires are the most common. While they may look bare, these wires have a thin but tough coating insulating them. Designing any electromagnetic coil or transformer is a complex process.

Most of the work focuses on insulating each part. The wires, pins, grounding plates, and magnetic core all ensure adequate insulation of different parts. So, it’s all about fitting all the materials that’ll perform greatly together and making sure the coil doesn’t burn up due to short-circuiting.

Why is Insulation Necessary?

Insulation of coils is necessary for two reasons:

1.  Uninsulated Coils Will Not Work

The result of lack of insulation is short-circuiting. A coil that’s short-circuiting won’t complete any turn. So, it’ll generate little to no energy. So, it’ll most likely not work. Even if it does, the

2.  Risk of Explosion

When a secondary coil in a transformer short circuit, it’ll produce a fault current that’s many times higher than the full load capacity. A major explosion will damage the coil unless the circuit breaker trips off immediately.

Types of Insulation Materials for Transformers

Several devices use coils. But the transformer is perhaps the most important. There are several materials for insulating coils and other parts of the transformer. They include

1.  Mineral Oil

Some transformers use mineral oil for insulation. This insulant has qualities that make it great such as its low cost, ability to transfer heat, and high dielectric strength. It can also recover quickly after dielectric stress. These qualities make mineral oil the most commonly used material for insulating transformers.

The insulation usually uses a barrier of wood-based paper board and enamel or wrapping paper. There’s direct insulation of the conductor with mineral oil to prevent potentially harmful streamers from forming in the oil. This further increases the strength of the structure.

The lead coming from the winding has heavy paper wrapping to reduce the stress in the oil. This moves the interface away from the conductor to another area with much lower stress. The oil stress will usually determine how heavy the wrapping will be. The minimum size of the conductor will depend on the thermal considerations.

2.  Askeral

This material refers to the group of synthetic chlorinated fire-resistant and aromatic hydrocarbons. They are also fluid-like oil and serve the same insulating purpose. When used for insulating transformers, the construction is similar to oil. Askeral has a high dielectric constant which transfers the dielectric stress to the transformer’s solid elements.

However, it’s not the best when it comes to recovery after dielectric stress. So, it’s seldom used in any transformer above 34.5-kV operating voltage. No one uses Askeral anymore due to their powerful nature as solvents. When they decompose, the products can be very harmful.

3.  Nitrogen and Air

These gases are also insulation materials. But they are only good for transformers with a maximum operating voltage of 34.5 kV. If you’re using an air-insulated transformer in a clean environment, you can leave it open to ventilate the atmosphere. But that’s not advisable if it’s a dirty place. Nitrogen has limited dielectric stress capacity. It usually operates at 1 atm with elevated operating temperature.

4.  Fluorogas

This material has lower heat transfer abilities compared to oil. But the dielectric strength is better than that of Nitrogen and air. Its higher density makes it superior to air and Nitrogen because it has a higher density. Pressure increases the heat transfer capacity and dielectric strength of this material. 

Most Fluorogas transformers operate at a pressure gauge of 3 atm. At that level, the dielectric strength is close to that of oil. Fluorogas uses other solid elements insulation for support. That includes barriers, disk or layer insulation, lead insulation, and layer insulation. Materials such as asbestos, glass, ceramics, and high-temperature resins.

If you’re using the transformer at a higher temperature, it’s better to use a Fluorogas transformer than oil-insulated transformers. It’s important to make sure you don’t overstress the gas. The dielectric stress on the gas is much higher than that of any solid insulation adjacent to it.

How to Insulate Regular Wires

It’s not only coils that require insulation. Even with the regular wires, there’s still a need to insulate it. If the wire isn’t already insulated, there are ways to insulate the wire. These include:

1.  Using Electric Tape

This general-purpose tape is the best way to insulate electric wires. They’re insulating materials, so they work against any material that conducts electricity. This could even be the damaged cable in your house. Most manufacturers use vinyl to make electrical tapes. It’s resistant to voltage, alkali, cold, and acid. It’s also fire retardant.

2.  Heat Shrink 

This shrinkable tube is also good for insulating wire. It’s a plastic tube that you surround wires with before you heat them with solder. It can withstand very high temperatures.

3.  Wire Nuts

Also known as wire connectors, it creates connections between electrical wires and termination. Mostly used for joining circuit wires in the house without soldering. There’s an insulator on the wire connector.

4.  Duct tape

You can use duct tape as an insulator. But it’s a temporary fix. It can only protect a low voltage and dry out over time because of the fibers. It’ll also wear out after a while.

5.  Friction tape

You can also use friction tape. They can replace electrical tapes as they’re resistant to weathering, moisture, solvents, and chemicals. But they don’t have a tensile strength at elevated temperatures.

In Conclusion

Insulation is essential for all coils. Without insulations, the coils won’t work and may even result in serious damage. Apart from coils, almost all electrical connections require insulation. Most come with a plastic covering. But if they don’t, you may have to insulate it yourself.