Modelowanie statycznych i dynamicznych stanów pracy małego silnika indukcyjnego

W pracy przedstawiono wyniki modelowania obwodowego i obwodowo-polowego charakterystyk elektromagnetycznych małego (370 W) silnika indukcyjnego przy biegu jałowym i w stanie zwarcia. Pomierzone charakterystyki pozwoliły na weryfikację obliczonych parametrów schematu zastępczego silnika. Parametry te zostały wykorzystane w obliczeniach obwodowych przebiegów rozruchowych silnika zasilanego napięciem sieciowym. Porównanie wyników wskazuje na dobrą adekwatność stosowanego modelu obwodowego.

In last years the speed-control drives with inverter-fed induction motors more and more are used. In inverter-fed motors additional phenomena due to high voltage/current harmonics may occur. Thus, the necessity to modify mathematical models of induction motor's should be taken seriously into consideration to make possible electromagnetic calculations in static and dynamic states as well. In the paper are presented the results of the electromagnetic characteristics' modelling of a small induction motor (370 W) using circuit method and circuit-field one as well, in no-load and short-circuit states of the machine. The modified motor's model should take into consideration the higher motor's harmonics as well as non linear phenomena such as magnetic circuit saturation, displacement of currents in rotor bars [3] and parametric resonance [5], if any, i.e. their influence on equivalent circuit parameters of the motor. Therefore, the calculation of motor's field distribution was necessary using field and circuit calculation methods. Next, these parameters have been used in order to calculate - using the circuit method - the start characteristics of the motor when supplying with network voltage. Applying the measured motor characteristics the verification of the calculated motor's equivalent circuit parameters has been done, in no-load and short-circuit states of the motor. The calculations and measurements of currents have been done when supplying motor with network sinusoidal voltage as well as with PWM inverter. Relevant results are shown in sequence in Fig. 2 (r.m.s. currents' values) and Fig. 3 (relative differences between calculated and measured currents related to measured value when supplying with sinusoidal voltage). In Figs 10, 11, 12 the measured and calculated courses of phase currents, electromagnetic torque and speed during free acceleration of the motor are presented. The comparison of measured and calculated results proves a good adequacy of the circuit model used.