DESIGN AND DEVELOPMENT OF INDUCTION HEATER
Submitted in partial fulfillment of the requirements for the award of
Bachelor of Engineering Degree in
Electricals and Electronics Engineering
by
R.VAISHNAVI (Reg. No. 3214286)
NEHA SINHA (Reg. No. 3214207)
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
FACULTY OF ELECTRICAL AND ELECTRONICS ENGINEERING
SATHYABAMA UNIVERSITY
JEPPIAAR NAGAR, RAJIV GANDHI SALAI,
CHENNAI – 600119, TAMILNADU.
APRIL 2016
SATHYABAMA UNIVERSITY
(Established under Section 3 of UGC Act, 1956)
Jeppiaar Nagar, Rajiv Gandhi Salai, Chennai - 600 119
www.sathyabamauniversity.ac.in
DEPARTMENT OF ELECTRICAL AND ELECTRONICS
ENGINEERING
______________________________________________________________________
BONAFIDE CERTIFICATE
This is to certify that this Project Report is the bonafide work of R.Vaishnavi (Reg. No.
3214286) and Neha Sinha (Reg. No. 3214207) who carried out the project entitled
“DESIGN AND DEVELOPMENT OF INDUCTION HEATER” under our supervision
from November 2015 to April 2016.
Internal Guide External Guide
(Name in capital letters (Name in capital letters
with signature) with signature)
Head of the Department
(Name in capital letters with seal & signature)
______________________________________________________________________
Submitted for Viva voice Examination held on ______________________________
Internal Examiner External Examiner
(Name in capital letters (Name in capital letters
with signature) with signature)
DECLARATION
We, R.VAISHNAVI (Reg.No. 3214286) and NEHA SINHA (Reg.No. 3214207) hereby
declare that the Project Report entitled “DESIGN AND DEVELOPMENT OF
INDUCTION HEATER” done by us under the guidance of Mrs.S.RADHIKA (Internal)
and Shri.J.PRABHAKAR RAO (External) at IGCAR, Kalpakkam is submitted in partial
fulfillment of the requirements for the award of Bachelor of Engineering degree in
Electrical and Electronics.
1.
2.
DATE : SIGNATURE OF THE CANDIDATES
PLACE :
ACKNOWLEDGEMENT
We are grateful to the almighty for the blessings showered on us to complete this
project work successfully.
We are highly thankful to the Chairman & Chancellor Col. Dr. JEPPIAAR, M.A., B.L.,
Ph.D., an icon in the arena of engineering education promotion, for having provided
ample facilities to our project work. We are also beholden to the directors Dr. Marie
Johnson, B.E., M.B.A., M.Phil., Ph.D., and Dr. Mariazeena Johnson, B.E., M.B.A.,
M.Phil., Ph.D., for their support.
We express our sincere thanks to the Vice-chancellor Dr. B.Sheela Rani, M.S. (By
Research), Ph.D., the registrar Dr.S.S.Rau., Ph.D., and the controller of examinations
Dr.K.V.Narayanan., Ph.D., for creating a conductive environment to proceed with our
project work.
We thank our head of the department Dr. Siva who gracefully accepted to do the
project in IGCAR, Kalpakkam. I am so thankful to my internal guide Mrs.S.Radhika,
professor, who inspired and guided us at every stage to design and develop the project
successfully.
We sincerely thank Shri.J.Prbhakar Rao, SO/E, and Mr.Jagadeesh Chandran who
directed us and helped us to complete the project in time. Our special thanks to
Shri.R.Ramakrishnan, Head, RCL, IGCAR for having permitted to do the project in
IGCAR, Kalpakkam.
We are also thankful to our EEE department staffs for rendering meaningful guidance.
And finally our parents and friends owe thanks from us for their love and help offered to
us throughout this project.
ABSTRACT
The design and development of an Induction Heater for a miniature high frequency
induction furnace is described. A background study into the fields of induction-heating,
resonance, power electronic, resonant converters and phase locked-loops are
performed with relevance to this research. An analysis of the resonant load circuit is
performed by means of a combination of measurement and numerical simulations. The
study of the load behavior and power source is used as a tool to aid effective
implementation of the automatic frequency control system. This simulation data is used
to determine the Operating frequency range of the RLL system. A background study is
performed in which several frequency-control schemes for power electronic converters
are investigated. A brief summary, in which the basic requirements for a frequency
control system with regards to this research are presented. Future suggestions for
optimizing the loop performance are presented. Further steps in the developmental
process of the miniature high frequency induction furnace are also discussed. A 1kW
prototype Induction Heater is designed to operate at frequency from 5kHz to 15kHz with
10kHz as central frequency. The system is using the high power MOSFET’s (500V,25A)
for the inverter section. This setup is tested with work pieces like nickel, stainless steel,
pure iron and aluminum. The system is checked for tuning the operating frequency to
resonant frequency for different work pieces.
TABLE OF CONTENTS
ACKNOWLEDGEMENTS SYNOPSIS
LIST OF ILLUSTRATIONS vi
1. Figures vi
2. Tables
CHAPTER 1
INTRODUCTION
CHAPTER 2
Previous work 4
2.1 Previous Induction Heating Reseal ch 4
2.2 Background Study 6
2.2.1. Current Source Inverter using SIT's for Induction Heating
Applications 6
2.3.1 High Power Ultrasound for Industrial applications
2.3.2 Discussion
2.4.1 Half— Bridge Inverter for Induction Heating Applications
2.5.1 PWM Inverter Control Circuitry for induction Heatinsi. 10
• Signal Conditioning 11
• Stability 11
• Speed 11
• Protection 12
• Initialization Procedure 13
CHAPTER 3 14
AN INTRODUCTION TO INDUCTION-HEATING AND PHASE LOCKED-
LOOPS 14
3.1 Background 14
3.2 Basics of Induction Heating 14
3.3 Hysteresis and Eddy-Current Loss 17
3.4 Power Source I8
3.5 Choice of Frequency 20
3.6 Eddy current stirring 22
3.7 Resonance 23
3.7.1 Parallel Resonance 24
3.8 Phase locked-loops
3.8.1 Loop Fundamentals -28
3.8.2 Phase Detector 28
3.8.2.1 4-Quadrant Multiplier 29
3.8.2.2 Switch type phase-detectors 30
3.8.2.3 Triangular phase detectors
3.8.2.4 XOR Phase Detector 33
3.8.2.5 R-S Latch 33
3.8.3 Loop filter 33
3.8.3.1 Passive loop filter 34
3.8.3.2 Active loop filter 34
3.8.3.2.1 Integrator and lead filter 34
3.8.4 Voltage Controlled Oscillator (VCO) 35
CHAPTER 4 36
IMPLEMENTATION OF AUTOMATIC FREQUENCY CONTROL 36
4.1 System description and operation 36
4.2 Loading Effect 37
4.3 Load circuit 38
4.3.1 Unloaded heating coil 39
4.3.2 Copper work-piece 40
4.3.3 Steel work-piece 40
4.2 Concept of resonance locking 41
4.3 Resonance locking methodology 43
4.3.1 Signal Measurement 44
4.4 Control circuit implementation 45
4.4.1 RLL revision 1 45
4.4.2 RLL revision 2 47
4.4.3 Discussion 48
4.4.4 Anti-Lock protection circuitry 49
CHAPTER 5 50
EXPERIMENTAL RESULTS 50
5.1 Revision I 51
5.2 Revision 2 53
CHAPTER 6 56
CONCLUSIONS AND RECOMMENDATIONS FOR FUTURE WORK 56
6.1 CONCLUSIONS 56
6.2 RECOMMENDATIONS FOR FUTURE WORK 58
REFERENCES
INTRODUCTION
Induction heating is a process which is used to bond, harden or soften metals or other conductive
materials.
BASIC INDUCTION HEATING SETUP
Induction heating relies on the unique characteristics of radio frequency (RF) energy - that portion of
the electromagnetic spectrum below infrared and microwave energy.
ALTERNATE TYPES OF HEATING
All industrial heating methods utilize one or more of three basic heat transfer methods:
● Conductive heating is the direct flow of heat through a material resulting from physical contact.
.
● Convection heating systems rely on heat transfer between a surface and adjacent fluid (gas,
air, liquid) and by the flow of fluid from one place to another induced by temperature.
● Radiation heating (electromagnetic radiation) does not require any transfer medium; thermal
energy is transferred through matter or space by electromagnetic waves - ultraviolet, infrared,
microwave, or radio frequency etc.
● Some other methods are –
● FLAME HEATING
● RESISTANCE HEATING
● TRADITIONAL OVENS AND FURNANCE
Advantages, drawbacks of inductive heating,
problems and practical issues
In comparison with other types of heating (gas heating, furnace, and flame), induction heating
presents several advantages:
● Accurate heating in term of amount of heat applied and area of heating
● No contamination of the treated part(non-contact heating)
● High heating rate and high efficiency
● No thermal inertia
Finally, security concerning induction is important, indeed, inductive heating can lead to several
problems in addition to those of conventional heating (risk of burns, fire):
● Electrical shocks, due to induced current in the work piece and its surrounding environment.
● HF frequency generation which can lead to interference with apparatus (network, computer,
control system)
● Magnetic field generation which can lead to dysfunction to pacemaker and other electrical
devices .
In a basic induction heating setup shown at above right, a sto be heated becomes a
short circuit secondary. When a metal part is placed within the inductor and enters the
magnetic field, circulating eddy currents are induced within the part.
Fig 2.1 Principle of induction heating
These eddy currents flow against the electrical resistivity of the metal, generating
precise and localized heat without any direct contact between the part and the inductor.
This heating occurs with both magnetic and non-magnetic parts, and is often referred to
as the “Joule effect”, referring to Joule’s first law – a scientific formula expressing the
relationship between heat produced by electrical current passed through a conductor.
Secondarily, additional heat is produced within magnetic parts through hysteresis –
internal friction that is created when magnetic parts pass through the inductor. Magnetic
materials naturally offer electrical resistance to the rapidly changing magnetic fields
within the inductor. This resistance produces internal friction which in turn produces
heat.
In the process of heating the material, there is therefore no contact between the
inductor and the part, and neither are there any combustion gases. The material to be
heated can be located in a setting isolated from the power supply, submerged in a
liquid, covered by isolated substances, in gaseous atmospheres or even in a vacuum.
2.2. IMPORTANT FACTORS TO CONSIDER
The efficiency of an induction heating machine for a specific application depends on
several factors: the characteristics of the part itself, the design of the inductor, the
capacity of the power supply, and the amount of temperature change required for the
application.
2.2.1. METAL OR PLASTIC
First, induction heating works directly only with conductive materials, normally metals.
Plastics and other non-conductive materials can often be heated indirectly by first
heating a conductive metal susceptor which transfers heat to the non-conductive
material.
2.2.2. MAGNETIC OR NON-MAGNETIC
It is easier to heat magnetic materials. In addition to the heat induced by eddy currents,
magnetic materials also produce heat through what is called the hysteresis effect. This
effect ceases to occur at temperatures above the “Curie” point - the temperature at
which a magnetic material loses its magnetic properties. The relative resistance of
magnetic materials is rated on a “permeability” scale of 100 to 500; while non-magnetics
have a permeability of 1, magnetic materials can have a permeability as high as 500.
2.2.3. THICK OR THIN
With conductive materials, about 85% of the heating effect occurs on the surface or
“skin” of the part; the heating intensity diminishes as the distance from the surface
increases. So small or thin parts generally heat more quickly than large thick parts,
especially if the larger parts need to be heated all the way through. Research has
shown a relationship between the frequency of the alternating current and the heating
depth of penetration: the higher the frequency, the shallower the heating in the part.
Frequencies of 100 to 400 kHz produce relatively high-energy heat, ideal for quickly
heating small parts or the surface/skin of larger parts. For deep, penetrating heat, longer
heating cycles at lower frequencies of 5 to 30 kHz have been shown to be most
effective.
2.2.4. RESISTIVITY
If you use the exact same induction process to heat two same size pieces of steel and
copper, the results will be quite different. Why? Steel – along with carbon, tin and
tungsten – has high electrical resistivity. Because these metals strongly resist the
current flow, heat builds up quickly. Low resistivity metals such as copper, brass and
aluminum take longer to heat. Resistivity increases with temperature, so a very hot
piece of steel will be more receptive to induction heating than a cold piece.
2.2.5. DESIGNING THE INDUCTOR
It is within the inductor that the varying magnetic field required for induction heating is
developed through the flow of alternating current. So inductor design is one of the most
important aspects of the overall system. A well-designed inductor provides the proper
heating pattern for your part and maximizes the efficiency of the induction heating
power supply, while still allowing easy insertion and removal of the part.
2.2.6. POWER SUPPLY CAPACITY
The size of the induction power supply required for heating a particular part can be
easily calculated. First, one must determine how much energy needs to be transferred
to the work-piece. This depends on the mass of the material being heated, the specific
heat of the material, and the rise in temperature required. Heat losses from conduction,
convection and radiation should also be considered.
2.2.7. DEGREE OF TEMPERATURE CHANGE REQUIRED
Finally, the efficiency of induction heating for specific application depends on the
amount of temperature change required. A wide range of temperature changes can be
accommodated; as a rule of thumb, more induction heating power is generally utilized to
increase the degree of temperature change.
2.3. BLOCK DIAGRAM
POWER SUPPLY
An induction heater consists of an electromagnet, and an electronic oscillator that
passes a high-frequency alternating current (AC) through the electromagnet. The
rapidly alternating magnetic field penetrates the object, generating electric currents
inside the conductor called eddy currents. The eddy currents flowing through the
resistance of the material heat it by Joule heating. In ferromagnetic (and ferromagnetic)
materials like iron, heat may also be generated by magnetic hysteresis losses.
The frequency of current used depends on the object size, material type, coupling
(between the work coil and the object to be heated) and the penetration depth.
