Recent Developments of Electrical Drives - Part 30. The book stating the recent developments of electrical drives, can be useful for engineers and researchers investigating and designing electrical and electronic devices as well as for students and young researchers dealing with electrical and electronic engineering, computer sciences (advanced computer modelling, sophisticated control systems with artificial intelligence tools applied, optimal design bye use of classical and genetic algorithms employed), applied mathematics and all the topics where electromagnetic, thermal, mechanical phenomena occur | II-12. Field-Circuit Finite Elements Models 283 Figure 16. Decomposition of measured current curve vs. time into exponential components for DC voltage V Figure 17. Decomposition of measured current curve vs. time into exponential components for DC voltage V. Figure 18. Decomposition of measured current curve vs. time into exponential components for DC voltage 138 V 284 Komçza et al. Table 3. Values of solution coefficients obtained from measured curves DC supply Us V Steady-state current A A1 A A1 Us Ü -S1 1 s A A A2 Us Ü -S2 1 s In Fig. 21 the relative permeability curves vs. time is shown a average for both stator and rotor core b average for one tooth pitch. The average value changes significantly and the permeability distribution is also different. The second important reason for the observed effect is a very well known skin effect in the rotor bars. As can be expected the current density distribution in the rotor bar changes considerably during the time Fig. 22 . The resulting value of equivalent rotor bar resistance and inductance changes too Figs. 23-25 . It should be emphasized that all described changes occur during the initial period when the stator current is compensated by rotor current. The main flux and magnetizing current do not grow as they occur in the final period when stator current goes to a constant value Figure 19. Relative permeability for time s. II-12. Field-Circuit Finite Elements Models 285 Figure 20. Relative permeability for time s. and rotor current disappears. According to these results it should be clear why constant parameter equivalent circuits sometimes used especially by Matlab Simulink users are not usable for transient simulation of induction machines. Therefore noticeable growth of scientific reports according to adjustable parameters .
