VARIABLE SPEED DRIVES USING THREE-PHASE CONTROLLED RECTIFIER AND INVERTER FED FROM A DC- LINK VOLTAGE SOURCE

The purpose of this report is to design of variable speed drives using three-phase,
half-wave controlled rectifier and inverter fed from a DC- link voltage source. These
devices are used in industry to vary the speed of DC as well as AC motors according
to the needs of a process.
The building blocks of Variable speed Drives are rectifier, DC link and the inverter.
The rectifier is used to rectify the incoming AC power from the supply into a DC
voltage. The DC link is used to smooth out the output of the rectifier. The output
from the DC link is fed to the inverter stage. The inverter changes this DC power into
AC power, to vary the speed of the AC motor.
For this project to be successful, there are a number of methods that were
implemented. Firstly, the literature review of the variable speed drives was made.
This was followed by the literature review of the firing circuit for the thyristor, the
filter design and the inverter design. Lastly the software which was mainly used to
simulate this design is Pspice.
The project is divided into to semesters, during the first semester of the project; the
firing of the SCR was designed. This was followed by the design of the complete
three-phase controlled rectifier, but this was only accomplished during the second
semester of the project. The simulation results of SCR triggering and the rectifier
shows that design was successful.
During the second semester DC Link as well as the inverter was to be designed. The
DC link design was successful as shown in the simulation results. And up to this
point, the rectifier can drive a DC motor. The design of the inverter is not yet
completed.