Types of Power Electronics Circuits

Power electronics circuits (also known as converters) can be classified into four types:

1a) Diode Rectifiers

• Also known as uncontrolled rectifiers.
• Converts ac input voltage (single phase or three phase) into fixed dc voltage.
• Application: Electric Traction, Battery Charging, Electroplating, Electrochemical processing, Power supplies, Welding, and Uninterruptible power supplies (UPS) system.

1b) AC to DC Converters

• Also known as phase controlled rectifiers.
• Converts constant ac voltage (single phase or three phase) into variable dc output voltage. 
• Use line voltage for their commutation, hence called as line commutated or naturally commutated converter. 
• Applications: DC drives, Metallurgical and chemical industries, and Excitation systems for synchronous machines (SM)

2) DC to DC Converters

• Also known as DC Choppers.
• Converts fixed dc input voltage into a controllable dc output voltage. 
• Requires forced or load commutation to turn off the thyristors. 
• For lower power circuits, Thyristor are replaced by power transistor. 
• Classified according to the type of commutation and also the direction of power flow.
• Applications: DC drives, Subway cars, Trolley trucks, and Battery driven vehicle.

3) DC to AC Converters

• Also known as inverters.
• Converts fixed dc input voltage into a variable ac output voltage. 
• Output may be variable voltage and variable frequency. 
• Use line, load or forced commutation for turning off the Thyristor. 
• At present, conventional Thyristor are also being replaced by GTOs in high power applications and by power transistors in low power applications. 
• Applications: Induction motor drives, Synchronous motor drives, UPS, HVDC transmission, and Induction heating.

4) AC to AC Converters

• Converts fixed ac input voltage into variable ac output voltage. 
• It is of two Types:

4a) AC Voltage Controllers

• Also known as AC Voltage regulators.
• Converts fixed ac input voltage directly into a variable ac output voltage at the same frequency. 
• Employ two Thyristor antiparallel or a TRIAC and turn off of both the devices is obtained by line commutation.
• Output voltage is controlled by varying the firing angle delay. 
• Applications: Lighting control, Speed control of fans, and Pumps.

4b) Cycloconverter

• Converts input power at one frequency to output power at different frequency through one stage conversion. 
• Line commutation is more common, through forced and load commutation may be employed. 
• Applications: Slow speed large ac drives like Rotary Kiln.

Note:

• The power semiconductor devices can operate as static switches or contactors also.

Reference

• M. H. Rashid, “Power Electronics: Circuits, Devices and Applications,” Prentice Hall India, Second Edition, 2006.
• P. S. Bimbhra, "Power Electronics," Khanna Publishers, fifth edition, 2012.