Influence of Magnetic Flux Controllers

on Induction Heating Systems, Computer

Simulation and Practice

Robert T. Ruffini, President

Fluxtrol Manufacturing, Inc. Auburn Hills, MI

Dr. Valentin S. Nemkov, Chief Scientist; Robert C. Goldstein, Research Engineer

Centre for Induction Technology, Inc. Auburn Hills, MI

Overview

• Magnetic Flux Control in Induction Heating

• Magnetic Flux Controller Application Technique

• Examples of Induction Coils with Magnetic Flux Controllers

• Conclusions

• Robot Guided Induction Heating Application

Technological Effects of MFC

Application

• Improved induction coil efficiency

• Better utilization of the workpiece power

• Magnetic field and heat pattern control

• Protection against unintended heating

• Improved power supplying circuitry

performance

• Elimination of external magnetic fields

Materials for Magnetic Flux

Control

• Laminations

• Ferrites

• Magnetodielectric

Materials (MDMs) 0

0.4

0.8

1.2

1.6

2

0 50 100 150 200 250Magnetic Field Strength

(A/cm)

Flu

x D

en

sity (

T)

MDM's

Laminations

Ferrites

B-H Curves for MFCs

Considerations for MFC

Selection • Relative magnetic permeability

• Operating frequency

• Core Losses

• Thermal resistance

• Ease of installation and removal

• Machinability

• Electrical resistivity

• Chemical resistance

• Cost

Typical properties of MDM’s

• Operating frequency: 50 Hz-5 MHz

• Temperature resistance: 150 - 350 C

• Initial relative permeability: 10 - 65

• Maximum permeability: 10 - 150

• Saturation flux density: 0.3 - 1.6 T

• Electrical resistivity: 100-10^7 Ohm-cm

Magnetic Permeability of

MDM’s for Induction Heating

0

25

50

75

100

125

150

0 50 100 150 200

Magnetic Field Strength

(A/cm)

Perm

eability Fluxtrol A

Fluxtrol A'

Fluxtrol B

Ferrotron

How to Apply MDM’s to Induction

Heating Coils

• Epoxy/Glue/Adhesive MFC to Copper Coil

– Prepare copper surface by removing machining oil or residual

quenchant

– Use thermally conductive, electrically non conductive epoxy

– Use epoxy with high temperature and thermal shock resistance

• Mechanically Fasten

– Soft solder or braze a brass bolt to copper inductor and drill clearance

hole in MFC

– Use a thermally conductive grease between copper coil and MFC

• Soft Solder (Fluxtrol A)

Camshaft Lobe Sintering Power

InductorTM

Clutch Plate Hardening Power

InductorTM

Camshaft Hardening Power

InductorTM

I.D. Hardening Power InductorTM

Conclusions

• Magnetic Flux Controllers Are an Important

Part of the Induction Technique

• Examples of Induction Heating Coils with

MDM controllers applied were shown

• Computer Simulation Can Accurately

Predict the Performance of Magnetic Flux

Controllers

Robot Guided Induction Scanning

Application Demonstrates:

1. The ability to treat complex shape parts with induction

robotic technique

2. Modern induction equipment suitable for robotic

scanning

3. Ability of computer simulation to predict the results of

heating

4. Demonstration of the magnitude of magnetic flux

controller influence

Demonstration Stand

1. Workpiece - S-shaped 1/2” thick steel plate water-

cooled on the back side

2. Specially designed hair-pin coil with Fluxtrol A

magnetic flux controller applied

3. ABB industrial robot

4. Hand-hold coaxial transformer with a flexible cable

(EFD)

5. EFD power supply Minac: 30 kW, 10 - 25 kHz

6. Close loop cooling system (Dry Coolers, Inc.)

Induction Coil Comparison

Coil without a concentrator Coil with Fluxtrol A

concentrator

Induction Coil with Magnetic

Flux Controller

Computer Simulation for

Process Design

Computer Simulation for

Process Design

Computer Simulation for

Process Design

Robot Guided Induction Scanning

Conclusions

• Magnetic Flux Controllers Make a Dramatic

Effect on Hair-Pin Coil Performance

• Computer Simulation Allows the Designer

Accurately Predict the System Parameters and

Heating Results

• Robotic Scanning Systems Can Be Used

Effectively in Flexible Production Line