This master's thesis deals with the operation of an induction motor. The induction motor is equipped with a frequency converter, which enables the adjustment of the rotational speed and the amplitude of the input voltage. Control with the scalar V/Hz method is more cost-effective than vector control, but there is excessive magnetization of the induction motor, which is especially evident in the motor’s efficiency at lower loads. The purpose of the thesis is to achieve optimal motor magnetization by adjusting the V/Hz ratio at different rotational speeds and torques and to improve the efficiency of the electric drive with an induction motor (EDIM).
In Matlab, we developed a system of numerical equations that describe the operation of an induction motor. Based on the results, we obtained the values of losses and efficiencies of the induction motor and the frequency converter, which we compared with the obtained measurements. Following this, we calculated the efficiencies and annual electricity consumption in the case of the operation of a 2.2 kW pump system and EDIM. In the final part of the thesis, we made a graphical interface in the design tool App Designer to facilitate the use of simulations.
By optimizing the magnetization of the induction motor, we successfully improved the efficiencies and reduced the losses of the induction motor and EDIM, which was most pronounced at low loads. The largest reduction in losses was shown in magnetization losses and in stator losses in the windings. The results obtained using the magnetization method of an induction motor show that it would be sensible to use them in industry where drive loads are lower than the nominal value, as this would reduce drive losses and at the same time reduce operating costs and extend plant operating life.