introduction:
Phase Controlled Rectifier
These convert constant AC voltage to variable DC output voltage .
These rectifiers use line voltage for their commutation.
These are also called line commutated or natural commutated AC-to-DC converters.
It is may be fed from a single phase or three-phase source.
It is mainly used in DC drives, metallurgical and chemical industries.
And excitation systems for synchronous machines.
Power Electronics Converters
CHOPPERS:-
A DC chopper converts fixed DC input voltage to a controllable DC output voltage.
The chopper circuits require forced commutation, to turn off the thyristors
For lower power circuits, thyristors are replaced by power transistors.
The classification of chopper circuits is dependent upon the type of commutation and on the direction of the power flow.
Choppers find wide applications in DC drives, subway cars, trolley trucks, battery-driven vehicles.
Control Strategies of Choppers
POWER ELECTRONIC CONVERTERS
AC VOLTAGE CONTROLLERS
These circuits also termed as AC voltage regulators, which convert fixed AC voltage directly to a variable AC voltage at the same
frequency .
These circuits consist of two thyristors in antiparallel, or a TRIAC, and are widely used for lighting control, speed control of fans,
pumps .
CYCLO CONVERTERS
These circuits convert input power at one frequency to output power at a different frequency through one-stage
conversion.
Line commutation is more common in these converters, though forced commutated cyclo converters are also
employed.
These are primarily used for slow-speed large AC drives like rotary kiln, etc.
INVERTERS
It converts DC-AC , use line or forced commutation . Us in IM, UPS and HVDC . SCR’s are replaced by GTOs in high-powered applications
Advantages Of Power Electronics
1.Flexibility in operation
2.High efficiency as there are less losses in devices .
3.High reliability
4.Lower cost
5.Fast dynamic response
6.Long life with less maintenance due to the absence of any moving parts.
Disadvantages Of Power Electronics
These circuits generate harmonics in the supply as well as in the load circuit and therefore deteriorates the performance.
Certain converters like AC to DC or AC to AC under certain operating conditions operate at a low input power factor (PF).
Regeneration of power is difficult in power electronic converter systems & Overload capacity of converters is low, and cost of converters is high.
Password : IIIEEEPED1
pdf made by Dr M Balasubbareddy