Computer Simulation of

Induction Heating Processes

Dr. Valentin Nemkov

Mr. Robert Goldstein

Centre for Induction Technology, Inc.

Auburn Hills, MI USA

Overview

• Benefits of Computer Simulation

• Special Features of Induction Heating

Computer Simulation

• Induction Heating Computer Simulation

Software

• Rule of Pyramid

• Computer Simulation Example

Computer Simulation Rules of Thumb

• Works for Any

Geometry and

Conditions

• Demonstrate the

Entire Dynamics of

the Process

• Leaves a Record for

Future Study

• Limitless Accuracy

• Good for Simple

Geometries

• Don’t Provide a Good

Understanding of the

Process

• Experience Isn’t

Passed On

• Case Dependent

Accuracy

Accuracy of Computer

Simulation

• Mainly Depends upon Description of

Material Properties

• Number, Distribution and Type of Elements

• System Description

Why Isn’t there One Comprehensive

Computer Simulation Software Package for

Induction Heating?

• Induction heating simulation involves a set of mutually

coupled non-linear phenomena

• Many induction applications are unique and may require

individual program structures

• Powerful personal computers with high processing speeds

and large available memory only recently became available

• The induction heating market is small compared to other

industrial sectors

• It is difficult to make an induction coil that doesn’t heat at

all and some users don’t care about design optimization

Process Control

Machine Operating Mode Power Supply Circuits

Thermal Process (Heating) Electromagnetic Process

Cooling Quenching Stresses

Structural Transformations Distortions

Specific Features of Induction Heating

Computer Simulation

Types of Programs for Induction Heating

Computer Simulation at CIT

PC simulation programs

Type Example

1D coupled Elta

2D Electromagnetic QuickField

2D Thermal Flux2D

2D Coupled Flux2D

3D Electromagnetic Flux3D

3D Thermal Flux3D

ELTA, 1-D Software Features

• User Friendly Interface with Very Fast

Solver

• Electromagnetic + Thermal

• Axisymmetrical or Plane Parallel

Geometries

• Database with Non-Linear Properties of

Materials

• Automatic Report Generation

Scanning Simulation Using

ELTA

QuickField, 2-D Software

Features

• User Friendly Interface

• Electromagnetic Only

• Linear Materials Only

• Fast Solver

• Inexpensive

Flux 2D, Software Features

• Less Friendly User Interface

• Electromagnetic + Thermal

• Material Database with Non-Linear

Properties

• Can Work in Conjunction with Other

Software (AutoCad, MatLab, etc.)

Flux 3D, Software Features

• Less Friendly User Interface

• Electromagnetic or Thermal

• Material Database with Non-Linear

Properties

• Tetrahedral, Cubic and Prizmatic Elements

3-D Simulation of Heat

Exchanger Joint Brazing

Rule of Pyramid

3D

2D, Electromagnetic or Thermal

1D, Electromagnetic + Thermal

2D, Electromagnetic +

Thermal

Computer Simulation of Seam

Annealing Process

Induction Seam Annealing

• Removes Stresses and Improves

Microstructure after Induction Seam

Welding

• High Production Rates, > 3 ft / s

• One of Two Induction Coil Styles Used:

Split-n-Return Vertical Loop

• No Published Studies on Coil Style

Selection

Case Study Conditions

• Tube: 1040 Steel

– 2” Diameter with 1/8” Wall

• Frequency 10 kHz

• Same Current Applied (2200 A)

• Production Rate 3.8 ft / s

• Flux Concentrator: Fluxtrol A

Half of Geometry Used For

Simulation, 2mm Grid

Vertical Loop Split-n-Return

Vertical Loop Inductors

Magnetic Field Lines

Return Leg Same Tube Return Leg Wider Tube

Vertical Loop Inductors, Final

Temperature Distribution

Return Leg Same Tube

Tmax 934 C Tmax 938 C

Return Leg Wider Tube

Vertical Loop Inductors, Flux

Density in the Concentrator

Return Leg Same Tube

Return Leg Wider Tube

Split-n-Return Inductor Magnetic

Field Lines

Split-n-Return Inductor Final

Temperature Distribution

Tmax 959 C

Split-n-Return Inductor, Magnetic

Flux Density in Concentrator

Table of Results of Simulation

Style Coil V Coil I Coil Loss Tube P Max T Efficiency Total Power

VL Same 378 2200 36.0 216 934 85.7% 252

VL Wide 321 2200 31.8 216 938 87.0% 248

SNR 272 2200 31.1 236 959 88.0% 267

Results of Study on Seam

Annealing

• Both Induction Coil Styles When Properly

Designed Work Effectively for the Seam

Annealing Process

• For Vertical Loop Inductors, a Wider

Return Leg Should Be Used

• Computer Simulation Is an Effective Tool

for Prediction and Study of Induction Seam

Annealing System Performance

Conclusions

• There are Many Advantages of Using

Computer Simulation

• The Specific Features of an Induction

Heating System must be Considered for

Computer Simulation

• The Rule of Pyramid is a Strategy for

Limiting the Time Required for Simulation