E-LEARNING BASED TEACHING OF ALTERNATING CURRENT ELECTRICAL MACHINES

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Bobon Andrzej, Kudla Jerzy, Miksiewicz Roman
Silesian University of Technology, Gliwice, Poland

• E-LEARNING BASED TEACHING OF ALTERNATING CURRENT
  ELECTRICAL MACHINES

FIGURE 1 STRUCTURE OF THE MODULE
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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.

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Purpose of the module AC - Electrical Machines

• The module is intended for students of
  universities of technology, specialization
  electrical 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

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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.

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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.

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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
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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.
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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 in
  them are explained in animations activated by a
  mouse when pressing the key PLAY.
• The animation consists in showing step by step
  the elements of the differential equation for
  one phase of the stator or one mesh of the
  rotor cage.
• The element corresponding to the shown equation
  element (circuit voltage, voltage drop along
  resistances, induced voltages) is simultaneously
  marked on the electrical diagram.

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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 active power
  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.

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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 computation results of the induction motor
  static characteristics for different RMS value
  and frequency of the stator voltage.

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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 synchronous generator 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.

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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 switching on and off.
• The lamps show whether the conditions for
  synchronisation of the generator with the
  infinite bus-bar system are met.

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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.

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CONCLUDING REMARKS

• The module AC Electrical Machines developed in
  the framework of the Inetele program aids
  giving lectures enabling presentation and
  explanation of difficult problems from the
  theory of electrical machines by means of
  interactive actions and animations in the main
  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 of AC Electrical
  Machines aiding the books on this subject.