E-LEARNING BASED TEACHING OF ALTERNATING CURRENT ELECTRICAL MACHINES

1. Boboń Andrzej, Kudła Jerzy, Miksiewicz Roman Silesian University of Technology, Gliwice, Poland E-LEARNING BASED TEACHING OF ALTERNATING CURRENT ELECTRICAL MACHINES FIGURE 1 STRUCTURE OF THE MODULE

2. Structure of the module: Presented module AC Electrical Machines is one of twenty-two modules from the field of electrical engineering which have been developed in the INETELE project realised in the framework of the EU Leonardo da Vinci program. project No CZ/02/B/F/PP/134009 • Each module consists of main screens, subscreens and screens containing the table of contents, list of denotations and their description as well as list of entries and index. • It was assumed that the main screen contains animations and the most important formulas, diagrams, figures and plots connected with the problem discussed. • The subscreens comprise the detailed description of the problem under consideration, that is: necessary explanations and derivations, as well as questions and exercise problems aiding the learning process. • The main screens can be used for lectures whereas the subscreens can be used for self-learning.

3. Purpose of the module “AC - Electrical Machines” • The module is intended for students of universities of technology, specializationelectrical engineering with Electrical Machines. • The module can also be used by academic teachers who lecture on the theory of electrical machines and by graduates who want to brush up and extend the knowledge from the Theory of Electrical Machines. • The module under consideration is an extension of the module Basic Principles of Electrical Machines developed in the framework of the Inetele project • Macromedia Flash program is used for developing the screens • Mathcad is used for simulations; its worksheets are included in some subscreens

4. Properties of the module • It was assumed that the electrical machine is a dynamic system, properties of which in steady and transient states can be determined basing on the analysis of solutions of the equations being the machine mathematical model. • the important part of the module includes the problems connected with formulating mathematical models of asynchronous and synchronous machines, methods for solving the equations being these models and physical interpretation of the results of the solutions. • The module was worked out in the form possible for presentation on web-sites with the use of interactive and animated in Flash technique elements.

5. The aim of animation and interactive graphics • to present constructions of electrical machines, • explain the principles for formulating their mathematical models, • present and interpret physically the solutions of the machine equations in steady and transient states, • learn and analyse the machine properties basing on the equivalent diagrams, vector diagrams and characteristics in steady states as well as waveforms in transients.

6. Layout of the AC Machines Module Contents AC machine constructions Mathematical models in phase coordinates Transient state Steady state Two-axis transormations Equations, equivalent circuits, vector diagrams Machine equations and equivalent circuits in dynamic states Analytical relations describing machine properties Analytical and numerical solutions Machine characteristics Dynamic waveforms

7. Exemplary main screens of an induction machine 1. Construction of an induction machine The screen presenting the most important elements of the induction machine construction. When one brings mouse cursor on any machine element, its name appears.

8. Exemplary main screens of an induction machine 2. Voltage equations of three-phase squirrel-cage induction motor • The way for formulating the differential equations and denotation of the quantities inthem are explained in animations activated by a mouse whenpressing the key PLAY. • The animation consists in showing “step by step” the elements of the differentialequation for one phase of the stator or one “mesh” of the rotor cage. • The element corresponding to the shown equation element (circuit voltage, voltagedrop along resistances, induced voltages) is simultaneously marked on the electricaldiagram.

9. Exemplary main screens of an induction machine 3. Power balance of a three-phase wound-rotor induction motor • The successive stages of animation show particular active powers in the machine both on the motor model and its equivalent diagram. • The flow of active power illustrates the way of conversion of the electric activepower supplied from the network by the stator windings into the mechanical power. • The presentation of the active power on the equivalent diagram enables determining the relationships that define the components of the power balance expressed by means of the stator and rotor currents and the equivalent diagram parameters. • The final stage of the power balance is determination of the relation for the machine electromagnetic torque.

10. Exemplary secondary screen ofan induction machine Simulation experiment in Mathcad program • The programs prepared in Mathcad are activated by means of appropriate links. • They allow conducting by one-self simulation experiments for different operating conditions, ratings and parameters of electrical machines. • The screen shows exemplary the code fragments and computationresults of the induction motor static characteristics for different RMS value and frequency of the stator voltage.

11. Exemplary main screens of a synchronous machine 1. Steady state equivalent diagram and phasor diagram • The screen presents the equivalent circuit of a salient-pole synchronousgenerator working alone, loaded with an impedance. • For the selected type of the load impedance (R, L, RL, RC) the exemplary vector diagram of the generator is shown. • The user, after choosing in the interactive mode the type of a synchronous machine and the kind of the load, sees step by step the way of constructing the generator vector diagram by means of animations.

12. Exemplary main screens of a synchronous machine 2. Synchronisation of a synchronous machine with the infinite bus-bar system • The user selects the kind of a synchroniser, sets the values of the field current and the speed of the machine rotor. • Animations show rotation of the vector diagrams of the generator and infinite bus-bar system voltages and changes of the bulb voltages, which cause their successive switchingon and off. • The lamps show whether the conditions for synchronisation of the generator with the infinite bus-bar system are met.

13. Exemplary main screens of a synchronous machine 3. Steady state characteristics • The user selects the active power loading the generator and activates the animation during which the V-curve for the chosen power is drawn point by point. • Simultaneously, the machine vector diagram changes appropriately.

14. CONCLUDING REMARKS • The module “AC Electrical Machines” developed in theframework of the Inetele program aids giving lectures enablingpresentation and explanation of difficult problems from the theory ofelectrical machines by means of interactive actions and animations in themain screens. • The lectures become more attractive and easier to understand. • The detailed explanations for the problems presented in the main screens are in the subscreens. • They, together with the derivations and questions, make self-understanding of the problems easier. • The programs in Mathcad environment included in the module allow carrying out simulation experiments for different ratings and parameters of electrical machines by one-self. • The module developed can be used for self-learning of the theory ofACElectrical Machines aiding the books on this subject.