Designing a Variable Frequency Drive

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Dr. Varjasi István
Department of Automation and Applied Informatics


We can find electric drives at many fields of industrial automatization. Usually, they are at production processes, they are employed for driving conveyors and many industrial machines.

One of the most widely used drives is the induction motor drive, because of the fine properties of this motor type. Synchronous motors are also often applied.

If we want to use either of them running in a closed-loop control mode at different rotation speed, then we need a variable frequency drive system. This is also suit to start these motors.

The alternate current motors are usually feed by voltage inverters. At modern drives the control algorithm is calculated by a digital signal processor.

The goal of my thesis project is to present the design of a small power, universal AC drive.

I worked on a programmable DC motor control equipment during my (BSc) self laboratory work.

I began the development of the AC drive during my (MSc) self laboratory work. I had came to know the inverters, and I had finished the schematics of the power electric part of it.

In my master thesis, the industrial drive solutions are presented, and I study the use of them. Then the system design of the Variable Frequency Drive is introduced, it is followed by the explanation of the schematics and layout designs and the software architecture. Finally, summary of test results and the directions of further development are documented.


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