INDUCTION HEATER USING RESONANT INVERTER WITH FEEDBACK USING PLL
Advisor:
Mr. Habib Wajid
Abstract:
This projects aims to implement Induction heating for metals, employing Single Phase Full Hbridge
voltage fed square wave inverter to power series resonant tank used along with coupling
transformer. IGBTs are used because of their high current capability with high frequency
operation. Driving signals and feedback is implemented via controller. Electrical Model is
simulated on MATLAB Simulink and observed output is a pure sinusoidal waveform across tank
circuit. The resonant frequency of LC tank is tracked using PLL which is implemented via PID
controller. A constant phase difference of 900 between voltage of inverter and tank capacitor
voltage ensures the condition of resonance and the process is achieved in real time. When work
piece is introduced inside the work coil, the inductance of the coil changes thus resonance
frequency also changes. The PID controller taking the feedback signals allows us to reach the
resonance frequency as quickly as possible after the insertion of work piece. Moreover, same
metal piece offer different inductance at different temperatures, this problem is also solved by
PLL.The performance parameters: Resonance frequency, Phase difference and temperature are
displayed on LCD. High temperature sensing is required, for that we have employed non-contact
IR Temperature sensor.