Induction Coils

Fluxtrol’s induction heating production services follow two workflows: one for customers building a new induction coil or application, and one for customers improving an existing coil or application. Both help engineer the coil, select and properly install the correct Fluxtrol SMC materials, and launch the process into production. The sections below walk through each workflow, then follow a detailed hairpin coil example from simulation to test.

Two workflows: new and existing applications

Pre-production induction applications

For customers that want to build a new induction heating coil or application, the Fluxtrol team follows this process:

1. Define a full application description to meet performance and functionality targets.
2. Deploy computer simulation .
3. Engineer the induction heating coil (design and engineering ).
4. Manufacture the coil (manufacturing ).
5. Compare simulation and testing: run the experiment and compare experimental results to simulation results (prototyping and validation ).

Existing-production induction applications

For customers that want to improve an existing coil or application:

1. Use simulation to describe and understand the existing application.
2. Run the experiment and acquire data.
3. Break down the application and draw the coil.
4. Deploy computer simulation to explain the results.
5. Compare the simulation to the results.
6. Propose new coil design and parameters, then test the new process (not applicable to the pre-production example below).

Detailed pre-production example: hairpin coil with Fluxtrol A

The example below follows the Fluxtrol pre-production workflow with Fluxtrol A. Many induction coil styles exist; a hairpin coil is used here for demonstration.

1. Application description and goal

Hairpin coils are commonly used in the induction heating industry to heat flat and non-flat surfaces. Magnetic controllers, especially soft magnetic composites (SMCs), are common with hairpin coils to increase efficiency and heat control.

The goal is to compare the heating performance of a hairpin coil with and without SMCs. For an easy comparison, Fluxtrol A SMC is applied to half of the coil while the other half has no controller. The coil is attached to a robot for scanning, which is common practice. Computer simulation analyzes and predicts the heating of a stainless-steel sheet, and a coil is designed and manufactured from the simulation results for testing.

2. Computer simulation

2D simulation. Plane-parallel static simulations using Flux 2D FEM software are run for both cross-sections. 2D is a simplification of the geometry and is sufficient in many cases. The results show a significant increase in temperature and efficiency for the hairpin coil with Fluxtrol A, for two reasons:

• The SMC concentrates the magnetic field, and the heating, below the coil.
• The SMC redirects the majority of the current from the internal faces to the bottom heat face.

3D simulation, full comparison. Full-geometry scanning simulations using Flux 3D FEM software account for the whole geometry but need longer setup and solve times. As in 2D, the section with Fluxtrol A SMC showed a significant increase in temperature and efficiency.

Simulation also predicts electrical parameters such as voltage, current, power and inductance. These predictions are used to choose the proper power supply and its tuning parameters. See example simulations .

3. Engineer the induction heating coil

After simulation, the coil is fully drawn in 3D for manufacturing. The engineering stage completes all coil details, such as the coil head, SMC design, water cooling path, mechanical components and insulation.

4. Manufacture the coil

Coils can be manufactured from copper tubing, machined copper, or both. In this hairpin coil, 1/2-inch rectangular copper tubing is used with Fluxtrol A SMC on one section, colored green. Rectangular tubing is more advantageous for SMC placement and adhesion, in addition to giving a flat heating face.

• Machining . Machining Fluxtrol A SMC is similar to machining light metals, using high-speed steel, tungsten carbide, TiN coated or AlTiN coated tools. Climb cut into the stock material, exit the detail and enter at the opposite end of the cut to meet in the middle.
• Applying . The Fluxtrol A SMC was applied to this hairpin coil with JB Weld epoxy.
• Protection . The SMC is coated with a green Cerakote coating, adding protection against corrosion.
• Maintenance . Like many coils, maintaining this hairpin coil is as simple as cleaning debris with a nylon bristle brush. An insulating material placed in the middle of the concentrator prevents a short circuit. Visual control of the concentrator and coil is key to spotting excess process residue that can lead to arcing.

5. Simulation and testing comparison

The coil was tested on an ABB robot arm, connected to an EFD power supply with a handheld transformer and a Dry Coolers closed-loop cooling system. The robot controlled the coil and scanned it over a stainless-steel sheet, following its curvature. The experiments behaved very much like the simulation: the Fluxtrol A section heated more than the section without SMC. Comparing simulation with experiment showed very strong agreement in the temperature distribution of the stainless-steel sheet.

Next steps

Whether you are planning a new coil or trying to fix an existing one, contact Fluxtrol with your part, process and power supply. See also R&D services for consulting, modeling and training.