Gradually, induction heating has been replacing conventional heating systems in several industries. After all, it provides pollution-free, localized, consistent, and precise heating.

However, most people don’t know that induction coil design influences heating efficiency.

This post discusses the basics of induction heating coil design. In addition, you will come to know what types of induction coils are available. But let’s first find out how an induction heating coil functions.

How Does an Induction Heating Coil Function?

The coil is the most prominent part of induction heating equipment. Its design and quality determine how effectively a workpiece will be heated.

An induction coil is copper tubing in the shape of a coil. Depending on how many turns are in the copper tube, the coil is called a helical or solenoid-wound coil.

When the power supply passes through the coil, it produces an electromagnetic field. It happens due to the flow of AC (alternative current).

This alternating electromagnetic field produces an induced current in the workpiece. And this current generates heat because of squared R losses.

How much current passes through the workpiece depends on the EMF intensity of the coil. This energy transfer is called the Eddy Current Effect or the Transformer Effect.

Types of Induction Coil

People have been using a wide range of coils for induction heating. These coils have different heating behaviors and applications. Let us learn about some common induction coil types.

Single-Turn Coil

The single-turn coil is also known as a solid inductor. This coil heats the workpiece with a narrow band. Apart from this, the coil can scan the length of the workpiece.

Internal Coil

The internal coil is known for its unique design. The coil can heat the inner surface of holes. The coil’s design ensures that the overall distance from the surface of the holes is lessened, helping optimum heat reach the holes.

Multi-Turn Helical Coil

A multi-turn helical or solenoid coil is a well-known induction coil featuring several turns. These turns express the length of the heating pattern.

Multi-Position Helical Coil

Multi-position helical coils are suitable for a complete heating process. This coil can have any number of positions. Nevertheless, up to eight positions are practical.

Curved Channel Coil

These coils are used on a rotary table. They help the operator occupy one step in the multistep assembly process.

Pancake Coil

Operators use this coil when a workpiece needs to be heated from one side only. Generally, it is suitable for flat-surface metals. In addition, the pancake coil can heat a small, narrow band from the center.

Hairpin Coil

A hairpin coil could be a single or multiple-turn coil. Generally, it helps you heat long and thin parts. Operators also use it to heat moving steel or aluminum.

Now you know about the different types of coils. Let us learn about the basics of an induction heating coil design.

Things to Keep in Mind When Designing an Induction Heating Coil

Induction heating coil design plays a role in the effectiveness of the induction heating process. As a result, it is crucial to make the best selection when choosing its components.

Tubing Selection

The tubing of the coil must have high-conductive copper. The copper tube with an outer diameter of at least 0.32 cm ensures easy water cooling.

Nevertheless, the diameter could be as large as 5.1 cm for applications that need high power.

Coil Turn Numbers

Multi-Turn coils are ideal for single-shot, large-diameter heating. These coils have multiple turns that increase the overall proportion of the coil. However, when the diameter of the coil exceeds 4x–8x, it becomes difficult to produce uniform heating.

Single-Turn Coils

Single-turn coils are suitable for heating bands with narrow diameters. The height and diameter of single-turn coils vary slightly with size.

Design of Coil Leads

The design and structure of the work-coil lead have the main influence on the performance of the coil.

The coil has a tank circuit. All the leads connecting the tank capacitor to the coil have inductance. When the coil heating area has a higher inductance, it counterbalances the effect of lead inductance.

Coil Bracing

Coil bracing is another crucial factor to consider when designing an induction coil. Coil bracing stops the magnetomotive force from making unwanted movements.

When electric current flows in the coil and workpiece, it generates magneto motive forces. The force can become uncontrollable during induction heating. Therefore, braces are crucial.

Distance of Coupling

Coupling is the term used for the gap between the induction coil and the workpiece.

For progressive heating, the coupling distance should be 0.19 cm.

However, if the workpiece is a magnetic material, the coupling distance should range from 0.25 to 0.38 inches.

The small gap between the coil and the workpiece is known as tight coupling, while the large gap is called loose coupling.

Coil Forming

Most manufacturers anneal the coil tubing every few bends. It prevents the deformation of the coil.

The tubing is heated until it becomes bright red. After that, it is cooled rapidly with water. The process prevents the coil from fracturing during fabrication.

Tools Used During the Coil Bending and Forming

Many tools are used to ensure a perfect induction heating coil design. Let us learn about some crucial ones below.


A caliper is a measuring tool that helps the manufacturer measure the different dimensions of the induction heating coil. In addition, the tool can measure the thickness of the coil.

Feeler Gauge

The Feeler gauge is another crucial tool used during coil forming. It helps engineers determine the gap widths in the induction heating coil turns. The instrument measures the spaces between the things that are close together.

Measuring Rod

Engineers use a measuring rod to measure the lengths of the coil’s survey areas.

Angle Ruler

Also known as an angle gauge, an angle ruler is a measuring tool that helps you measure the inner and outer angles of the workpiece.

Flow Meter

Flow Meter is another crucial instrument used when designing the induction coil. The coil generates a lot of heat due to the current passing through it.

Therefore, the coil is cooled with the help of cooling water flowing inside the copper tube. The flow meter helps you detect if the pressure and flow rate of the cooling water is appropriate. It should be as per the diameter of the copper pipe.

If it is inadequate, it might not minimize the heat effectively, resulting in burnout. Apart fro

Electrician Meter

An electrician meter helps you detect if the current is passing appropriately. To install an induction heating coil onto the connector, it needs brazing. Therefore, it is important to check if the current is passing normally.

Induction Brazing Machine

Engineers utilize induction brazing machines to join copper inductance coils together.

Induction Coil Installation

Like its design, the proper installation of the induction coil is crucial. An incorrectly installed induction coil might cause several hours of downtime. Following the manufacturer’s manual for coil installation or replacement is advisable.

Keep the following points in mind when replacing the coil on an induction heating device.

  • Make sure the main switch and cooling water are turned off.
  • Place a container beneath the inductor to collect the leaking cooling water.
  • Carefully release the thrust parts by loosening the nuts on the connector jaws.
  • Pull the inductor out and install the new coil.
  • Tight fit the coil and the coaxial transformers.

Note: Always use brass nuts and washers.

The induction heating coil is the most crucial part of the induction heating machine. As a result, induction heating coil design takes many considerations.

So this is the in-depth guide on an induction heating coil, its design, functioning, types, and more. We hope this gives you adequate knowledge on the subject.

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