3 February 2018

Types of power electronics converters

A term power electronics system in electronics science consists of one or more power electronic converters. A power electronic converters are made up of some power semiconductor devices controlled by the integrated circuit.

Broadly speaking power electronic converters can be classified into six types under :

  • Diode rectifier
  • AC to DC converters
  • DC to DC converters
  • DC to AC converters
  • AC to AC converters
  • Static switches

1. Diode Rectifier :

A diode rectifier is an electronic circuit convert AC current known as input voltage which periodically reverses direction to a fixed DC voltage which flows in only one direction. The input alternating voltage may be single phase or three phases. This process is known as rectification. 

Diode rectifiers find wide use in electric traction, battery charging, electroplating, electrochemical processing, power supplies, welding, and uninterruptible power supply systems.

2. AC-DC Converters  ( Phase Controlled Rectifiers ) :

AC to DC converter is electrical circuits that transform alternating current ( AC ) input into direct current ( DC ) output. These rectifier use line voltage for their communication. 

AC to DC converter is mainly used in power electronic applications where the power input is a 50 Hz or 60 Hz sine-wave AC voltage that requires power conversion for a DC output. 

It may be fed from one phase or three-phase source. It is used in DC drives, metallurgical and chemical industries, excitation systems for synchronous machines etc.

3. DC-DC Converters ( DC Choppers ) :

DC to DC converters is an electronic circuit or electromechanical device that converts a source of direct current from one voltage level to another one. It is also known as DC choppers. 

DC chopper circuit is needed to forced, load, commutation to turn off the thyristors. Thyristors are replaced by power transistors for the lower power circuit.

Classification of the chopper circuit is dependent upon the types of DC communication and also on the direction of power flow. It finds wide application in DC drives, subway cars, trolley trucks, battery driven vehicles etc.

4. DC-AC Converters ( Power Inverters ) :

DC to AC converters is an electronic circuit that changes direct current ( DC ) to alternating current ( AC ). DC to AC converter is also called power inverters. Output current may be variable current and variable frequency. 

This types of converter find wide use in induction motor and synchronous motor drives, induction heating, UPS, HVDC, and transmission etc. 

Power inverters use load, line, or forced commutation for turning off the thyristors. 

At present, the conventional thyristor is also being replaced by high power application and by power transistors in low power application.

5. AC-AC converters :

AC to AC converters is an electronic circuit converts an AC waveform to another AC waveform, where the output voltage and frequency can be set arbitrarily. In other words, it converts fixed AC input voltage into a variable AC output voltage. 

There are two types of AC to AC converters : 

  • AC Voltage Controllers 
  • Cyclo Converters 
AC voltage controllers convert fixed AC voltage directly to a variable AC voltage at the same frequency. It is based on either thyristors, TRIACs, SCRs, or IGBTs which converts a fixed voltage, fixed frequency alternating current electrical input supply to obtain a variable voltage in output delivered to a resistive load. 

The output voltage is controlled by varying the firing angle delay and turn off device is obtained by line communication. 

They are widely used for lighting control, speed control of fans, pumps etc.

Cyclo converters convert AC, power at one frequency into AC power of an adjustable but lower frequency without any direct current. It converts input power at one frequency to output power at a different frequency through one stage conversion. 

Line commutation is more common in cyclo converters so that forced and load commuted cyclo-converters are also employed. 

They are primarily used for slow speed large AC drives like rotary kiln etc.

6. Static switches :

The static switch is an electrical device that switches a load between two sources. Some switches are manual that an operator affects the transfer by throwing a switch, while others are automatic when they sense one of a source has lost or gained power.

The static switches are called AC static switches or DC static switches depending upon the input supply. 

Explore more information:

1. Advantages and disadvantages of power electronics converters