M.

Sc Thesis Proposal(Revised)

GUI based Design and implementation of induction heating

Supervisor

Dr. Gulam Abbas

(Assistant Professor)

Department Of Electrical Engineering

Submitted by

Mian Usman Zahid

(MSEE 01131026)

The University Of Lahore

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Table of Contents

1 Abstract...............................................................................................................................................2

2 Introduction.........................................................................................................................................2

2.1 Working of Induction Heating Furnace:...............................................................................................3

3 Related literature and research...........................................................................................................4

4 Motivation...........................................................................................................................................6

5 Problem Statement and Objective.......................................................................................................7

6 Proposed Methodology.......................................................................................................................7

7 Expected Results..................................................................................................................................8

8 References...........................................................................................................................................9

9 Time Line...........................................................................................................................................11

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 Project Title: GUI based Design and implementation of induction heating
furnace using (PLL) Method

1 Abstract

The main objective of this research work is to design and implement an induction heating
furnace. Afterwards next aim is to create a Personal Computer (PC) based Graphical User
Interface (GUI) and inter-communicating hardware that helps furnace to communicate with the
PC for monitoring and control purpose. Prime motive of research is to design and implement an
induction heating furnace using controller based phase lock loop controlling method. This
furnace will be able to reach to a desire temperature at set frequency. The temperature, consumed
power and other variables can be monitored on GUI. Microcontroller is used to communicate
hardware with PC. Controller provides two kinds of services here. First control of induction
heating furnace and second is to build an interface between the hardware and PC. That assembles
the incoming real time information and plots in a manner which is easy to understand by the user.
The PC based GUI helps the user to interact with the hardware in a convenient manner. The
temperature information of heating object and values of other control variables (like current,
voltage and power consumed) are sent to the PC using serial communication. The human
computer interaction is built in appropriate software to provide a convenient interface which will
allow the user to set the controlling parameter like (protection and required heat) and also to plot
its response. The GUI will be used to observe and analysis the essential parameters of furnace.
In addition the user interactive property of GUI will help user to have efficient and convenient
control of furnace.

2 Introduction

All induction systems are developed using electromagnetic induction which was first discovered
by Michael Faraday. Electromagnetic induction refers to the phenomenon by which electric
current is generated in a closed circuit by the fluctuation of current in another circuit places next
to it. The basic principle of induction heating, which is an applied form of Faradays discovery, is
the fact that AC current flowing through a circuit affects the magnetic movement of a secondary
circuit located near to it. Heat loss, occurring in the process of electromagnetic induction could
be turned into productive heat energy in an electric heating system by applying this law. Many
industries have benefited from this new breakthrough by implementing induction heating for
furnacing, Quenching and welding.

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2.1 Working of Induction Heating Furnace:
A source of high frequency electricity is used to derive a large alternating current through a coil
as shown in Figure 1. This coil is known as the work coil. The passage of current through this
coil generates a very intense and rapidly changing magnetic field in the space within the work
coil. The work piece to be heated is placed within this intense alternating magnetic field.

Figure1: Block diagram of Induction Furnace.

Depending on the nature of the work piece material a number of things happen. The alternating
magnetic field induces a current flow in the conductive work piece. The arrangement of work
coil and the work piece can be thought of as an electrical transformer. The work coil is like the
primary where electrical energy is fed in, and the work piece is like a single turn secondary that
is short circuited. This causes tremendous current to flow through the work piece. These are
known as eddy currents.

In addition to this, the high frequency used in induction applications gives rise to a phenomenon
called skin effect. This skin effect forces the alternating current to flow in the thin layer towards
the surface of the work piece. The skin effect increases the effective resistance of the metal to the

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passage of large current. Although the heating through the eddy currents is desirable in this
application, it is interesting to note that the transformer manufacturers go to great lengths to
avoid this phenomenon in their transformers. Laminated transformer core, powdered iron cores
and ferrites are all used to prevent eddy currents from flowing in side transformer cores.

Inside a transformer the passage of eddy current is highly undesirable because it causes heating
of the magnetic core and represents power that is wasted.

2.2 Basics of Phase Locked Loop:

VCO OUTPUT
ERROR LOOP FILTER VCO
DETECTOR

FEEDBACK
DIVIDER

Figure 2: Basic Phase Locked Loop (PLL) Model

As shown in the above Figure 2 the basic blocks of the PLL are the Error Detector (composed of
a phase frequency detector and a charge pump), Loop Filter, VCO, and a Feedback Divider.
Negative feedback forces the error signal, e(s), to approach zero at which point the feedback
divider output and the reference frequency are in phase and frequency lock.

Referring to Figure 2, a system for using a PLL to generate higher frequencies than the input,
the VCO oscillates at an angular frequency of ω O. A portion of this signal is fed back to the error
detector, via a frequency divider with a ratio 1/N. This divided down frequency is fed to one
input of the error detector. The other input in this example is a fixed reference signal. The error
detector compares the signals at both inputs. When the two signal inputs are equal in phase and
frequency, the error will be constant and the loop is said to be in a “locked” condition.

3 Related literature and research

Due to the diversity and improbability of the high power loads, the power controls of medium-
frequency power are a time-varying and non-linear system. Moreover, the process of temperature

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control shows characteristics such as big inertia, long time-delay and nonlinearity, so it is very
difficult to construct the accurate mathematical model for the temperature control system, and
conventional PID controller is difficult to achieve the ideal results. As fuzzy control is a kind of
intelligent control method, that is why it has been used widely and effectively in the past years.
The most significant merit of fuzzy control is that not required mathematical model of
objectives. This method uses fuzzy logic to illustrate the control experience as a group of rules,
and then using fuzzy sets to quantify the rules, thus make the system to execute the rules
according to human’s manipulating experience automatically and exactly [1].

There are assorted types of converters acclimated for consecration heating as rotary converters.
Its use is for medium frequency applications (250 Hz to 10 kHz). They abide about of a three-
phase asynchronous motor powered by the 60Hz electric arrangement and mechanically
accompanying to a single phase alternator at the appropriate frequency. This supplies the load the
amount formed by the inductor and compensation capacitors. The operating frequency is fixed
because the coupling between induction motor and the alternator remains fixed. Currently the
rotary converters are outdated and replaced by static converters with better performance. Years
after with the development of electronic rotary converters were replaced by static thyristor
converters operating at a low frequency (3-10 kHz) but afforded bigger achievement compared to
the rotary converters. At present assorted types of converters are acclimated for induction heating
applications, resonant converters are broadly acclimated because of zero voltage switching and
zero current switching with which losses can be minimized. [2].

Inverter topologies are the more active branch of induction heating fields, which has full-bridge
and half-bridge inverter topology. Full-bridge topology is mostly used for high power output
occasions because of its high cost and complexity. However, in low-cost and small-power-level
practical applications the half-bridge inverter is mostly popular because of better better
performance, simple control, high efficiency and the lower voltage stress of the switching
elements. ZVS turn-on, ZCS turn-off is not considered half-bridge inverter topology with
increased switching losses. This paper adds switch snubber capacitances based on the
conventional half-bridge topology, that limits the rise rate of the collector current at the moment
of the switching conduction and the collector voltage at switching turn-off, i.e. di / dt and du/dt
,respectively. Thus it will avoid the collector voltage and current simultaneously reach the
maximum values, which will reduce switching losses during transitions. [3].

Due to better efficiency, cleanliness and safety, induction heating cooktops are becoming more
popular. Spiral n-turn winding placed beneath of a metallic vessel is the basic part of induction
heating system, fed by a power electronic inverter. Without any restriction of dimensions, shape
and quantity of the pots, conventional cooktops with fixed burners are changing to total-active
surface appliances. The most common arrangement consists of many reduced-size inductors each
one supplied with an inverter. The major disadvantage of this arrangement is the high
manufacturing cost. Pursuing a potential cost reduction, especially in small size inductors, and
following the trend of other applications, where the integration of passive components in PCB

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entails important research efforts, the implementation and design of PCB inductors for domestic
induction heating has been analyzed. These implementations present several advantages such as
good repeatability and ease of manufacturing [4].

Major problems of medium frequency induction furnace are the large inertia, serious delay,
nonlinear parameters and complex structure, it is difficult task to meet the requirements with PID
controller. An adaptive PID control program is proposed based on the RBF neural network, using
neural network identifier online identification system model to get PID controller parameters
auto-adjusting real-time and on-line. So the control system would be able to maintain the
indicators in ideal range, having a better balance between the robustness and controllability and
improvement of performance between dynamic heating process and static. What’s more, the
system’s capability of anti-jamming has made enhancement [5].

A high frequency inverter is developed for a high frequency induction heating furnace. This
circuit was used for the implementation of ZVS LCL resonance method. In this paper IGBT
20MVA are used at the frequency of 100kHz for LCL resonant induction heating equipment
during the development process, 100kHz IGBT module development process and understanding
gained from the design of LCL resonant Zero Crossing through the PLL control over operation
of the IGBT Soft Switching, and focused on minimizing losses. In addition, through the actual
design and implementation of devices using the area to test drive the development of large
inverter technology based on the test [6].

Matlab- GUI (graphical user interface) is a tool which allows users to perform tasks interactively
and programmatically. This tool can be used for developing a software package for
comprehensive performance analysis of single phase SEIG(self excited induction generator). In
this paper, a unified model of the generator is developed using Matlab- GUI tool which accepts
input of different capacitor topology connections [7].

In this paper a GUI (graphical user interface) using MATLAB tool boxes is used for complete
analysis, design and capacitor estimation under different operating conditions. GUI facility is
shown to be an effective tool for the design to visualize the results.GUI will help one to arrive at
needed design/ analytical output in a short time. In this software package nonlinear equations are
solved by a numerical based routine ‘Fsolve’ in the tool box of MATLAB to find the values of
saturated magnetizingreactance Xm and the output p. u. frequency F for the given values of
machine parameters such as RL, Xc, and v [8].

Aim of the research is to design GUI based software tool that can facilitate the user for accurate
and speedy analysis of SEIG (self excited induction generator).. The mathematical models have
been programmed in script files (M-files) using conventional MATLAB language in GUI
environment to represent all the operating conditions of a SEIG which makes it a very user
friendly design tool. This will provide the interactive windows for all simulated operating
conditions [9].
The process of induction heating has become a convenient method for heating metals or
conductive materials in industrial processes, such as melting, surface hardening, brazing,
soldering, welding, tempering and annealing, forming and extrusion, etc. With the advancements
in power semiconductor switching devices and microprocessors, Super audio-frequency

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induction heating power supplies are becoming more reliable and cost-effective and have better
performances. To keep the inverter in resonant state in the heating process, control circuit must
have the ability to trace frequency automatically to meet the need of load variation. Furthermore,
with the raising of the inverter’s output frequency, tracing circuit should be quicker and more
accurate. Thus phase lock loop (PLL) is widely used in induction heating apparatuses [10].

4 Motivation

Induction heating eliminates the inconsistencies and quality issues associated with open flame,
torch heating and other methods. Once the system is properly calibrated and set up, there is no
guess work or variation; the heating pattern is repeatable and consistent. With modern solid state
systems, precise temperature control provides uniform results. Power can be instantly turned on
or shut off. With closed loop temperature control, advanced induction heating systems have the
capability to measure the temperature of each individual part. Specific ramp up, hold and ramp
down rates can be established & data can be recorded for each part that is run.

Induction heating systems do not burn traditional fossil fuels; induction is a clean, non-polluting
process which will help protect the environment. An induction system improves working
conditions for your employees by eliminating smoke, waste heat, noxious emissions and loud
noise. Heating is safe and efficient with no open flame to endanger the operator or obscure the
process. Non-conductive materials are not affected and can be located in close proximity to the
heating zone without damage.

This uniquely energy-efficient process converts up to 90% of the energy expended energy into
useful heat; batch furnaces are generally only 45% energy-efficient. And since induction requires
no warm-up or cool-down cycle, stand-by heat losses are reduced to a bare minimum. The
repeatability and consistency of the induction process make it highly compatible with energy-
efficient automated systems.

Matlab- GUI (graphical user interface) is a tool which allows users to perform tasks interactively
and programmatically. This tool can be used for developing a software package for
comprehensive performance analysis of induction heating furnace.

5 Problem Statement and Objective

The term "User Interface" refers to the methods and devices that are used to accommodate
interaction between machines and the, users, who use them. User interfaces can take on many
forms, but always accomplish two fundamental tasks: communicating information from the
product to the user, and correspond permissible from the user to the product. GUI provides the
interaction between the end-user, and the functions behind the interface. Without this interaction,
the GUI would not have any purpose. Main focus is to interface the hardware with the computer

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for the convenience and to maintain connection with hardware in an efficient and reliable manner
remotely. For such activity

 Controller is used to control the power of furnace and temperature of work piece and to
create an interface between Hardware and PC.

 The PC based GUI helps the user to interact with the hardware in a convenient manner

6 Proposed Methodology

The main objective is to design and implement an induction heating furnace, in which
Inverter is the most important part of the induction heating furnace. Working frequency and
output power of inverter will decide the furnace’s frequency and power. A GUI based interface
will be designed to operate with the available hardware. The main intermediate device that will
be used for interfacing the hardware with the computer will be microcontroller. Block diagram of
proposed methodology is shown in Figure 3.

Figure: 3 – Block Diagram of proposed Methodology

7 Expected Results

Following are some of the result that is expected to be achieved at the end of this research work
in the form of software and hardware.

1. Design and hardware of an induction heating furnace.

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2. Design of the GUI for monitoring and controlling purpose. That GUI may include:

a. ON, OFF switch.

b. Temperature controls (center, right and left).

c. Graph plots.

3. Programming of the controller for the proper interfacing with the hardware.

4. Design of an Interfacing circuitry.

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8 References

[1] Zheng, Z., Guocheng, W., & Xiaowei, L. (2010, October). An Intelligent Monitoring
System of Medium-Frequency Induction Furnace Based on Fuzzy Control. In Intelligent
System Design and Engineering Application (ISDEA), 2010 International Conference
on (Vol. 1, pp. 261-264). IEEE.

[2] Fernandez, O., Delgado, J., Martinez, F., Correa, J., & Heras, M. (2013, November).
Design and implementation of a 120A resonant inverter for induction furnace. In Power,
Electronics and Computing (ROPEC), 2013 IEEE International Autumn Meeting on (pp.
1-6). IEEE.

[3] Zhou, Y., Yang, R., & Li, Y. (2013, May). An improved ZVZCS half bridge inverter
applied to small power level induction heating device. In Control and Decision
Conference (CCDC), 2013 25th Chinese (pp. 2274-2277). IEEE.

[4] Lope, I., Carretero, C., Acero, J., Burdio, J. M., & Alonso, R. (2013, March). Printed
circuit board implementation of small inductors for domestic induction heating
applications using a planar litz wire structure. In Applied Power Electronics Conference
and Exposition (APEC), 2013 Twenty-Eighth Annual IEEE (pp. 2402-2407). IEEE.

[5] Zheng, Z., Xiao-Wei, L., & Guo-cheng, W. (2010, October). The Study of Intelligent
Control of Medium Frequency Induction Furnace Based on RBF Neural Network.
In Intelligent System Design and Engineering Application (ISDEA), 2010 International
Conference on (Vol. 2, pp. 740-743). IEEE.

[6] Yoo, H., Shim, E., Kang, J., Choi, G., Lee, C., & Bang, B. (2011, May). 100kHz IGBT
inverter use of LCL topology for high power induction heating. InPower Electronics and
ECCE Asia (ICPE & ECCE), 2011 IEEE 8th International Conference on (pp. 1572-
1575). IEEE.

[7] Pradana, A., Sandeep, V., Murthy, S. S., & Singh, B. (2012, December). Acomprehensive
MATLAB—GUI based performance evaluation of three winding single phase SEIG.
In Power Electronics, Drives and Energy Systems (PEDES), 2012 IEEE International
Conference on (pp. 1-6). IEEE.

[8] Murthy, S. S., Bhuvaneswari, G., Ahuja, R. K., & Gao, S. (2010, October). A novel
MATLAB graphical user interface based methodology for analysis, design and capacitor
estimation of self excited induction generators. In Industry Applications Society Annual
Meeting (IAS), 2010 IEEE (pp. 1-6). IEEE.

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[9] Murthy, S. S., & Ahuja, R. K. (2010, November). Design and analysis of three phase Self
Excited Induction Generator using MATLAB Graphical User Interface based
methodology. In Power, Control and Embedded Systems (ICPCES), 2010 International
Conference on (pp. 1-5). IEEE.

[10] Cui, Y. L., He, K., Fan, Z. W., & Fan, H. L. (2005, August). Study on DSP-based PLL-
controlled superaudio induction heating power supply simulation. InMachine Learning
and Cybernetics, 2005. Proceedings of 2005 International Conference on (Vol. 2, pp.
1082-1087). IEEE.

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9 Time Line

Task Duration
Proposal Submission 2 weeks

Proposal acceptance 2 weeks

Literature survey 2 weeks

Algorithm and design 3 weeks

Simulation and Results 3 weeks

Report writing 1 week

Submission of thesis and Final viva 3 weeks

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Comments of Supervisor:

Signature of Supervisor Signature of Student

___________________ __________________

Endst. No. Univ / _____________ Dated:_______________

The above duly proposal recommended by the departmental board of studied/ committee of Post-
Graduate studies in its meeting held on ______________ is forwarded to the Director of
Research for obtaining the approval of the Vice-Chancellor.

Chairman
Department of Electrical Engineering
The University Of Lahore.

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Aims of the research paper of (Analysis of Various Parameters of Self-excited Induction
Generator Using MATLAB/GUI) by Deeksha Choudhary is the complete evaluation of steady-
state behavior and mathematical modeling of self excited induction generator and to stimulate
different operating parameters like

(i) Effect of stator resistance on terminal voltage

by designing a graphical user interface using MATLAB.

Aims of this research is to implement an induction heating furnace, designing a GUI and
interfacing it with the furnace using some hardware to stimulate and to control some of the
operating parameters of the furnace for example:

(i) Temperature of the work piece

As described in the title of proposal that Phase Locked Loop will be used for the controlling
purpose of the furnace; a phase-locked loop is a feedback system combining a voltage controlled
oscillator (VCO) and a phase comparator so connected that the oscillator maintains a constant
phase angle relative to a reference signal. Phase-locked loop can be used, for example, to
generate stable output high frequency signals from a fixed low-frequency signal.

As it is mentioned that we want to operate our furnace at resonance frequency so that maximum
power could be delivered. To keep the circuit at resonance we use RLC resonance tank designed
for a fixed resonance frequency. This RLC resonance tank consists of coupling or impedance
matching transformer, capacitor bank, work coil and a work piece, in that circuit we set the value
of capacitor so that capacitive reactance could cancel out the combined inductive reactance of
coupling transformer, work coil and work piece at a fixed frequency. As the work piece could be
of different materials and could have different ferromagnetic properties at different frequencies
as inductance of iron, steel and aluminum decreases as the frequency increases and similarly
their resistivity increases with the increase in the frequency, so the properties of different
materials could disturb resonance, to avoid that problem phase locked loop arrangement will be
used. A PLL consists of three parts: A voltage controlled oscillator (VCO), a loop filter and a
phase detector. The VCO output derives the device or the inverter gate. It also closes the loop by
feeding itself back into the phase detector so that it can get compared with reference. The VCO
generates a 50% duty cycle square wave; the frequency depends on the input voltage to the VCO.
The higher the VCO input voltage the higher the VCO output frequency; the lower the voltage
the lower the frequency. The PLL phase detector compares the phases of two inputs: the

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reference signal from capacitor bank and the VCO out frequency. The phase detector could be a
XOR gate.

Phase detector generates a square wave whose width is based on the phase difference of the two
signals. If the two waves are 90 degrees out of phase the average output of the phase detector
will be equal to the half of its biased voltage. The loop filter takes the phase detector output and
converts this to the input voltage to the VCO. The simplest filter is a RC low-pass filter. The cut-
off frequency will determine how sensitive the PLL is to phase changes, and how well it stays
locked on the reference signal. At resonance the tank current is real and in phase with the coupler
transformer voltage, which is in phase with the inverter voltage. The tank capacitor voltage lags
the tank current by 90 degrees; therefore, it lags the inverter voltage by 90 degrees. Now as the
workpiece heats its ferromagnetic properties change. The workcoil becomes a variable inductor
and affects the resonant frequency of the tank. If the effective resonance goes down, it seems to
the circuit that we increased on drive frequency to the tank. This makes the tank more inductive.
Inductance causes the source voltage lead the tank current. That is, the tank current is forced to
lag the inverter voltage. The capacitor voltage initially lagged the current by 90 degrees. This
means the capacitor voltage lags the inverter voltage even more.

An increase in inductive reactance is the same as if we increased our inverter drive frequency.
We lower it by decreasing the voltage to VCO input voltage. As capacitor voltage V c shifts more
to the right of inverter output Vinv the XOR region increases. However, we need it to decrease in
order to yield a lower voltage for VCO. We achieve this by inverting V c. Now as inverted Vc
shifts to the right, output voltage of phase detector V phi decreases. We integrate this to a voltage
value and use this for VCO input. A smaller VCO input results in a lower frequency and we stay
in resonance. At resonance inverter voltage and current are in phase the inverter voltage leads the
tank capacitor voltage by 90 degrees. Vphi is half of half a pulse width. The average voltage is
half of the biased voltage. So, half voltage at VCO input will keep us close to resonance. The
problem is that resonance frequency changes with different workpieces and during heating.
However, the PLL will adjust itselft to maintain a lock on the phase relationship.

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