POWER ELECTRONICS

UNIT I: Thyristor Silicon controlled rectifier (SCR), construction and principle of operation, two-transistor analogy, static and dynamic characteristics, gate characteristics, ratings, series and parallel operation of SCRs, over voltage and over current protections, protection against high di/dt and high dv/dt, use of UJT for pulse generation. UNIT II: Phase Controlled Rectifiers Principle of phase control, performance parameters, single-phase half wave and full wave controlled rectifiers, mid point and bridge converters, full controlled converters, half controlled converters, comparison between full and half controlled converters, three-phase half wave and fully controlled bridge converter, three-phase semi-converter, effect and source inductance in single-phase and three-phase bridge converters, commutation or overlap angle, effect of overlap. UNIT III: DC To DC Conversion Principle of chopper operation, controlled strategies, step up chopper, step down chopper, chopper configuration, forced commuted chopper, voltage commutated chopper, current commuted chopper, Load commuted chopper, Jone’s chopper, Morgan chopper. UNIT IV: Inverter Classification of inverters, voltage source inverter, current source inverter, series resonant inverter, modified series resonant inverter, parallel inverter, bridge inverter, auxiliary commuted single-phase inverter, complementary commuted singe-phase inverter, and three-phase inverter, Cyclo-converters: basic principle of operation, step-up and step down single-phase to single-phase Cyclo-converter. UNIT V: Speed Control Of DC Motors Four-quadrant operation of series and shunt DC motors, constant HP and constant torque operation, various schemes of speed control (single converter, double converter, chopper), modern semiconductor devices, power transistors, power bipolar junction transistors, steady state characteristics, switching characteristics, switching limits, safe operating area, power MOSFET: steady state characteristics, switching limits, safe operating area, IGBT: steady state characteristics, safe operating area.