Damir Žarko

THE APPLICATION OF FINITE ELEMENT METHOD FOR MORE ACCURATE CALCULATION AND ANALYSIS OF TURBOGENERATOR PARAMETERS

The paper describes a computation of basic electromagnetic parameters of a turbogenerator using 2D finite element method with completely automated preprocessing. The results obtained by 2D method are compared to the ones obtained by classical (analytical) method and to the measured values from tests carried out on a 194 MVA turbogenerator manufactured by KONCAR-Generatori, Zagreb, Croatia. It appears that finite element method combined with analytical method gives more accurate results than analytical method and that the computation time can be quite acceptable.

Optimized Design of a Brushless DC Permanent Magnet Motor for Propulsion of an Ultra Light Aircraft

The paper presents an optimized design of a low mass brushless DC (BLDC) permanent magnet motor for propulsion of an ultra light aircraft. The optimization has been carried out using Differential Evolution algorithm implemented in Matlab combined with SPEED and MotorCAD software packages for electromagnetic and thermal modeling of the BLDC motor using ActiveX technology. The credibility of the models created with SPEED and MotorCAD has been confirmed by comparing the results of simulation and measurement performed on a 12 kW synchronous permanent magnet motor available in the laboratory. The goal of the optimization has been to minimize the weight of the motor under condition that the motor delivers rated power of 15 kW at rated speed of 3000 rpm with hot-spot temperature not exceeding the temperature limits of class F insulation (155 °C). Two optimal BLDC motor designs with slot/pole combinations 12/10 and 18/16 have been obtained. The motor with 18 slots and 16 poles yields the highest torque density with the lowest mass of active parts (copper+laminations+magnets) of only 5.1 kg.

Constrained field-oriented control of permanent magnet synchronous machine with field-weakening utilizing a reference governor

ABSTRACT This paper presents a complete solution for constrained control of a permanent magnet synchronous machine. It utilizes field-oriented control with proportional-integral current controllers tuned to obtain a fast transient response and zero steady-state error. To ensure constraint satisfaction in the steady state, a novel field-weakening algorithm which is robust to flux linkage uncertainty is introduced. Field weakening problem is formulated as an optimization problem which is solved online using projected fast gradient method. To ensure constraint satisfaction during current transients, an additional device called current reference governor is added to the existing control loops. The constraint satisfaction is achieved by altering the reference signal. The reference governor is formulated as a simple optimization problem whose objective is to minimize the difference between the true reference and a modified one. The proposed method is implemented on Texas instruments F28343 200 MHz microcontroller and experimentally verified on a surface mounted permanent magnet synchronous machine.

Extended Space Vector Method for Calculation of Induction Motor Parameters

Abstract In this article, a novel method for the determination of spatial vectors of multi-phase windings is proposed. The proposed method is applied to squirrel-cage induction motors and it allows for the calculation of the rotor currents space vectors with any slot number (even and odd), that cannot be determined by classical expressions. On the basis of current space vectors and current flux linkages, the proposed method determines the flux linkage phasors. The current and flux linkage phasors of the stator and rotor make it possible to determine the leakage and magnetizing inductances of the rotor and stator for any operating point on the basis of finite-element analysis of the motor model without any further calculations. The new method, besides the motor parameters, allows determination of the motor torque components developed by higher harmonic components of current, which significantly affects the resultant motor torque. The validity of the proposed method is verified by comparison of motor parameters determined from finite-element analysis with the parameters determined by running no-load and locked rotor tests on an actual motor.

Magnetically Nonlinear Iron Core Characteristics of Transformers Determined by Differential Evolution

An optimization based method for determining magnetically nonlinear iron core characteristics of transformers is proposed. The method requires a magnetically nonlinear dynamic model of the transformer as well as voltages and currents measured during the switch-on of unloaded transformer. The magnetically nonlinear iron core characteristic is in the model accounted for in the form of three different approximation functions. Their parameters are determined by the stochastic search algorithm called differential evolution. The optimization goal is to find those values of approximation functions parameters where the root mean square differences between measured and calculated currents are minimal. The impact of individual approximation functions on calculated dynamic responses of the transformer are evaluated by the comparison of measured and calculated results.