Converters: An Introduction
The term "Converters" is used to refer a system which transforms one form of electrical energy into another form of electrical energy. For example AC into DC or DC into AC. Here conversion of ac into dc is called as "rectification" and conversion of dc into ac is known as "inversion".
In this page we are going to see brief introduction about various power electronics converter circuits.
Depending on the type of source and the type of load, the power electronics converter circuit comes into the following categories:
AC to DC = Rectifiers
DC to DC = Choppers
DC to AC = Inverters
AC to AC = AC Voltage Controllers
AC to DC Converters: (Diode Rectifiers)
A diode rectifier circuit converts ac input voltage into a fixed dc voltage. The input voltage may be single phase or three-phase.
Please click here to understand the Diode Bridge Rectifier Circuit.
Click here to know about Comparison of various types of rectifiers
AC to DC Converters: (Phase Controlled Rectifiers)
These circuits convert constant ac voltage to variable dc output voltage. These rectifiers use line voltage for their commutation. These are used in dc drives, chemical industries, synchronous machines. Phase controlled converters may be fed from single phase and three-phase source.
DC to DC Converters: (DC Choppers)
- A dc chopper converts fixed dc input voltage to a controllable dc output voltage.
- The chopper circuits require forced, or load commutation to turn-off the SCR.
- For low power circuits we can use Power BJTs. Choppers are used in dc drives, battery driven vehicles etc.
Please click here to know about principle of operation, applications, types of chopper
DC to AC Converters (Inverters):
An Inverter converts fixed dc voltage to a variable ac voltage. The output may be a variable voltage and variable frequency. Inverters find wide use in induction motors and synchronous motor drives, Induction heating, Uninterruptible Power Supply (UPS), High Voltage DC (HVDC) Transmission etc.
AC to AC Converters:
These circuits convert fixed ac input voltage into variable ac output voltage. These are of two types of AC to AC converters namely AC Voltage Controllers and Cycloconverters.
AC Voltage Controllers:
These converter circuits convert fixed ac voltage directly to a variable ac voltage at the same frequency. These circuits employ two BJTs in antiparallel or a triac. Output voltage is controlled by varying the firing angle delay.
- These circuits convert input power at one frequency to output power at a different frequency through one stage conversion.
- These are mainly used for slow-speed large ac drives like rotary kiln etc.
Please click here to know about the basics, types and applications of Cycloconverters
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