The present master’s thesis describes the development of a variable frequency drive for three-phase asynchronous induction motors for the purpose of driving the fans. It deals with the theory of induction motors with squirrel cage and their specific characteristics with regard to their dependency of variable frequency control. The characteristics of the fan as a load are described. The following is an overview of the various principles of control of power switches and their advantages and disadvantages. The next chapter describes the implementation and operation of the developed prototipe. The system is based on a microcontroller, IGBT transistors and high-voltage gate driver. For current measurements a Hall effect sensor is used. Additional safety features are protections against overvoltage, overcurrent and overtemperature. Through the user interface the user can monitor the current measured variables and also change settings. The emphasis is on the description of the firmware and algorithms. In conclusion the measurements with a fan are presented and possibilities for further develompent of the product are discussed.
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