TYPES OF POWER ELECTRONIC DEVICES

A POWER ELECTRONIC SYSTEM CONSISTS OF ONE OR MORE POWER ELECTRONIC CONVERTERS. A POWER ELECTRONIC CONVERTER IS MADE UP OF SOME POWER SEMICONDUCTOR DEVICES CONTROLLED BY INTEGRATED CIRCUITS. THE SWITCHING CHARACTERISTICS OF POWER SEMICONDUCTOR DEVICES PERMIT A POWER ELECTRONIC CONVERTER TO SHAPE THE INPUT POWER OF ONE FORM TO OUTPUT POWER OF SOME OTHER FORM.

1. DIODE RECTIFIER

A DIODE RECTIFIER CIRCUIT CONVERTS AC INPUT VOLTAGE INTO A FIXED DC VOLTAGE. THE INPUT VOLTAGE MAY BE SINGLE-PHASE OR THREE-PHASE. DIODE RECTIFIERS FIND WIDE USE IN ELECTRIC TRACTION, BATTERY CHARGING, ELECTROPLATING, ELECTROCHEMICAL PROCESSING, POWER SUPPLIES, WELDING, AND UNINTERRUPTIBLE POWER SUPPLY UPS SYSTEMS.

2. AC TO DC CONVERTERS (PHASE-CONTROLLED RECTIFIERS)

THESE CONVERT CONSTANT AC VOLTAGE TO VARIABLE DC OUTPUT VOLTAGE. THESE RECTIFIERS USE LINE VOLTAGE FOR THEIR COMMUNICATION, AS SUCH THESE ARE CALLED LINE-COMMUTATED OR NATURALLY-COMMUTATED AC TO DC CONVERTERS. PHASE-CONTROLLED CONVERTERS MAY BE FED FROM A 1-PHASE OR 3-PHASE SOURCE. THESE ARE USED IN DC DERIVES, METALLURGICAL AND CHEMICAL INDUSTRIES, EXCITATION SYSTEMS FOR SYNCHRONOUS MACHINES

3. DC TO DC CONVERTERS (DC CHOPPERS)

A DC CHOPPER CONCERTS FIXED INPUT VOLTAGE TO A CONTROLLABLE DC OUTPUT VOLTAGE. THE CHOPPER CIRCUITS REQUIRE FORCED, OR LOAD, COMMUTATION TO TURN OFF THE THYRISTORS. FOR LOWER POWER CIRCUITS, THYRISTORS ARE REPLACED BY POWER TRANSISTORS. CLASSIFICATION OF CHOPPER CIRCUITS IS DEPENDENT UPON THE TYPE OF COMMUTATION AND ALSO ON THE DIRECTION OF POWER FLOW. CHOPPERS FIND WIDE APPLICATIONS IN DC DERIVES, SUBWAY CARS, TROLLEY TRUCKS, BATTERY-DRIVEN VEHICLES

4. DC TO AC CONVERTORS (INVERTOR)

AN INVERTER CONVERTS FIXED DC VOLTAGE TO A VARIABLE AC VOLTAGE. THE OUTPUT MAY BE A VARIABLE VOLTAGE AND VARIABLE FREQUENCY. THESE CONVERTERS USE LINE, LOAD, OR FORCED COMMUTATION FOR TURNING OFF THE THYRISTORS. INVERTERS FIND WIDE USE IN INDUCTION-MOTOR AND SYNCHRONOUS-MOTORS DRIVES, INDUCTION HEATING, UPS, HVDC TRANSMISSION.