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