الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Induction heating was first noted when it was found that heat was produced in transformer and motor windings. It uses high frequency electricity to heat materials that are electrically conductive. Induction heating is achieved by applying a high frequency electric source through a coil. The passage of current through this coil generates a very intense and rapidly changing magnetic field in the space within the work coil. It is a very efficient heating scheme since the heat is actually generated inside the work piece
Induction heating can be used for any application where we want to heat an electrically conductive material in a clean, efficient and controlled manner such as welding and brazing, hardening metals, sealing the anti-tamper seals of medicine, induction cooking, and zone purification used in the semiconductors manufacturing industry.
The power used in heating can be controlled by many methods. It can be achieved by using a high frequency converter to convert the dc to ac with high frequency. However; the switching losses at high frequency introduce a serious problem. Switching also causes an EMI problem, because a large amount of di/dt and dv/dt is generated in the process.
To overcome these problems and reduce the switching losses, soft switching methods are used. The voltage or current administered to the switching circuit can be set to zero by using the resonance created by an L-C resonant circuit. High frequency resonant converters are used widely for induction heating. This thesis presents a modular resonant inverter to achieve the desired high frequency with reduced switching losses. A hybrid soft switching technique based on the Pulse Width Modulation (PWM) and the Pulse Density Modulation (PDM) is proposed for the modular inverter to control the furnace temperature. Matlab/Simulink software package is used to evaluate the dynamic performance of the proposed system. Simulation results confirm that the load current is sinusoidal with the desired frequency at different conditions. Moreover, the proposed hybrid switching scheme is a Zero Voltage Switching (ZVS) technique.