Recent Developments of Electrical Drives - Part 11. 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 | I-8. Coupled FEM and System Simulator 87 phase voltage load torque FEM computation S-function phase current electromagn. torque angular speed angular position flux linkage Figure 4. Functional block of the FEM computation. Table 1. Characteristics of the asynchronous motor drive Asynchronous motor Frequency converter En 2 MW En 9 MW Cn 3150 V Cmax 3300 V In 436 A Imax 1645 A ZN 40 Hz TN 0-75 Hz nN 792 rpm and the load torque on the shaft are given as input variables and the phase currents electromagnetic torque rotor position and the stator flux linkage are obtained as output variables. The mathematical coupling between the FEM model and SIMULINK is weak which means that the internal variables of the subsystems are solved separately and updated to each other with one-step delay. Accordingly there is no need to use uniform step size in the whole model which provides flexibility and computation-effective simulation due to the different timescales in the system model. Characteristics of the motor model Table 1 presents the ratings and characteristics of the drive including the asynchronous motor and the frequency converter. Because of symmetry the finite element mesh of the motor covers half of the cross section comprising 13 143 nodes and 6 518 quadratic triangular elements. The geometry of the modeled region is presented in Fig. 5. Figure 5. Geometry of the asynchronous motor model. 88 Kanerva et al. Results Steady-state operation In order to study the steady-state operation of the drive the time-stepping simulation was run at 600 rpm which is about 75 of the nominal speed. The nominal torque 24 kNm was applied resulting in the nominal stator current. The time step was qs for the drive model with analytical motor model. When the measurement and control are modeled in different time levels it takes 66 s to run 1 s simulation on a 900 MHz Pentium 4 PC Matlab release 13SP1 . The same case was also simulated with FEM motor model when qs time step was used for
