A power converter is an electrical circuit that converts the electrical energy from one form into the desired form optimized for the specific load. This conversion can be from direct current to alternating current to direct current to increase or decrease the magnitude of the input voltage, invert polarity, or produce several output voltages of either the same polarity as the input, different polarity, or mixed polarity, such as in the computer power supply unit. Converters are available in the form of a simple transformer or may be more complex, depending on the application. This article will discuss what power converters are and their different types.
Table of Content
What is Power converters?
- Types of Power converters
- AC-DC Converters
DC-DC Converters
DC-AC Converters
AC-AC converters
Types of Power Converters
1. AC-DC Converters (Phase Controlled Rectifiers)
An AC to DC converter is an electrical circuit that transforms alternating current ( AC ) input into direct current ( DC ) output. These rectifiers 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 a one-phase or three-phase source. It is used in DC drives, metallurgical and chemical industries, excitation systems for synchronous machines, etc.
2. DC-DC Converters (DC Choppers)
A DC-to-DC converter is an electronic circuit or electromechanical device that converts a source of direct current from one voltage level to another. It is also known as DC choppers.
A DC chopper circuit is needed to force, load, and commute 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.
3. DC-AC Converters (Power Inverters)
DC to AC converters is electronic circuits that change direct current ( DC ) to alternating current ( AC ). A DC-to-AC converter is also called a power inverter. 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 applications.
4. AC-AC converters:
AC to AC converters is electronic circuits that convert an AC waveform to another AC waveform, where the output voltage and frequency can be set arbitrarily. In other words, it converts a 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 convert 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 the turn-off device is obtained by line communication.
The output voltage is controlled by varying the firing angle delay, and the 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.