hrvatski

Analiza stacionarnih karakteristika tiristorski upravljanog kaveznog asinkronog motora

This thesis defines a procedure for evaluation of caracteristics of the voltage-controlled sqquirel-cage induction motor without neutral wire. An appropriate model of the thyristor voltage controller and induction motor has been developed. In the model, beck to beck thyristors have been substituted by ideal switches, and induction motor has been modeled in two variants: with neglected rotor skin-efect, and with rotor skin-efect taken into consideration. On the basis of the comprehensive mathematical model of the thyristor voltage controller - induction motor system, software for computer simulation has been made. The typical steady-state modes with variation of the delay angle and load torque have been simulated. The simulation results of the voltage and current waveforms of the voltage-controller-fed induction motor drive for different operating point have been analysed. For those modes of operation, the harmonic analysis of current and voltage has been made. Simulation results of waveforms and harmonics of the voltage and current have been compared with measurements done on the laboratory setup for the same operating points. The laboratory setup consists of the soft-starting device (thyristor converter) and 2.2 kW induction motor. The close match of the simulation and experimental confirms correctness of the mathematical model. The method for evaluation of losses of nonsinusoidal supplyed induction motor has been defined. The metod is based on the results of harmonic analysis of voltage and current. On the basis of evaluation of losses and efficiency of induction motor with neglected rotor skin-effect, we have come to conclusion that increasing of the delay angle, at small loads, reduces losses, i.e. increases efficiency. Analysis of the results obtained with the model with rotor-skin effect shows that efficiency is reduced when rotor skin-effect is taken into consideration. This phenomenon indicates the need to study if for larger motors reduction of voltage results with increased efficiency, since the rotor copper losses could be significant. Finally, efficiencies obtained by simulation and experiment have been compared.

asinkroni kavezni motor; naponsko upravljanje; stacionarne karakteristike

nije evidentirano