Elektricne masine i postrojenja   TE4EMP

Rezultati 1. kolokvijuma              Nacin ocenjivanja na 1. kolokvijumu

Rezultati 2. kolokvijuma i zakljucne ocene

Zadaci i resenja na 2. kolokvijumu

Osnovne informacije o predmetu, skripta, zadaci, kolokvijumi, uputstva

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Electric Machines, Apparatus and Systems

regular subject for EL and AU option students,
7th semester, 3 +  1 + 1

Lecturer: Prof. Slobodan N. Vukosavic, boban@ieee.org,

teaching assistant: Zeljko Pantic, binella@kondor.etf.bg.ac.yu

    In brief: Fundamentals of electromechanical energy conversion. Principle of operation, dynamic and steady state characteristics of: DC machines, Tesla's induction machines and synchronous machines. Overview of reluctance, linear motors,  SR machines,  permanent magnet servo motors.  Fundamentals of electric energy generation, transmission and distribution. Low frequency power transformers, turbines and generators, transmission lines, power system control and protection.

    Introduction. Fundamental concepts, magnetic materials and circuits, induced voltages, magnetic field energy and coenergy. Basic energy conversion processes: accumulation, electric-to-electric conversions, transmission, electromechanical conversion. Electromechanical system modeling, generalized state variables, Lagrange relation.
    Electrostatic and magnetic machines: system of charged conductors in E-field, system of current contours in H-field. Mechanical subsystem, degrees of freedom, force and torque generation. Transformer and dynamic EMF, EMF and torque relation for single-fed and doubly-fed electromechanical converters. Model of electromagnetic machine, approximations, matrix form of the voltage balance equations, inductance matrix, torque generation and Newton equation. Power losses and power balance, current and flux density limits, thermal resistance and time constant, size-torque relation.
    Idealized cylindrical machine, electromagnetic field in the air gap, Pointing vector calculation in cylindrical air gap space, radial and tangential power flow. Quasi Sinusoidal Winding distribution and the space filtering effect. The flux and the EMF in a Q-S distributed winding. Self and mutual inductance of Q-S dist. windings. Sinusoidal distributed stator and rotor currents. DC and AC cylindrical machines. Multi-phase windings, polyphase currents, generation of the revolving field.
    DC machines. Construction: elements of magnetic circuit, stator and rotor windings, commutator and brushes. Basic operation principles. Torque and EMF generation. Excitation field, armature reaction field. Linear commutation, auxiliary poles and their windings, compensation windings.  DC generators, excitation types and the output characteristic. Mechanical characteristic of separately excited DC motor, exploitation and transient M-W characteristics. Power losses and efficiency. Mechanical characteristic of series excited DC motor. Dynamic model of separately excited DC motor, starting, braking, speed control. Permanent magnet DC motors and their use in servo drives. Basic static power converters for the DC motor supply and control.
    Tesla's asynchronous motor(AM)  Elements of magnetic circuit, stator yoke, slots and teeth, the rotor lamination and the forms of rotor slots. 2-pole 3-phase stator windings, multiple pole windings;  dye-casted aluminum (squirrel-cage) rotor windings, wound slip-ring rotor windings. Principle of operation: revolving field, synchronous speed and the slip frequency, the rotor EMF and current, torque generation. Modeling: 2-phase equivalent of the 3-phase machine, voltage balance equation and the inductance matrix for the 2 stator and 2 rotor physical windings. Rotational coordinate transformation into flux-synchronous (dq) coordinate frame. Dq-frame dynamic model, power balance, torque expression, mechanical losses and the Newton equation.
    Derivation of the steady-stateequivalent circuit. Revolving filed power, the slip power and the rotor power. Power losses and power balance in the steady state. Steady-state torque expression, mechanical and natural M-W characteristic of the AM;  braking, motoring and generating regions. Breakdown torque. Phasor diagram with the AM MMF, flux, EMF and currents in the steady state. Starting torque and currents of the fixed frequency supplied AM. Starting (inrush) performance improvements through the frequency dependence of the rotor parameters (deep rotor slots, double cage). Effects of the rotor bar geometry on the mechanical characteristics. Fixed frequency supplied AM speed regulation through the voltage adjustment, pole pairs changing, external rotor resistance variation. Single-phase induction motor operation principles.
    Variable frequency supplied AM,  M-W characteristic frequency and voltage dependence. Breakdown torque in the field weakening, M-W curve in the field weakening with constant power and constant current. Exploitation and transient M-W characteristics of a variable frequency supplied AM. Critical speed and its parameter dependence. Fundamentals of the AM control. Drive power converter topologies and the torque/speed control approaches.
    Synchronous machines (SM)   Rotor magnetic circuit and windings; magnetic anisotropy and saliency, permanent magnet excitation, slip-ring electromagnet excitation, rotational transformer contactless excitation, the rotor of a reluctance SM. Windings and magnetic circuit on the stator. Principle of operation: revolving field, synchronous revolution of the rotor field and the stator MMF and flux wave. Dynamic model in the synchronous frame. Steady state equations and equivalent circuit. Phasor diagram of the stator current, flux and the EMF for symmetrical and salient pole machine. Power angle and the torque - angle relation. Electromagnet and reluctance torque. Mechanical characteristic and the peak torque capability. Active and reactive power dependence on the power angle and the excitation current. Stability of the synchronous generator response to the prime mover torque disturbance. The role of damping windings. Transient and sub-transient response of a synchronous generator. Fixed frequency supplied synchronous motors, characteristics, power losses and balance, startup procedures and synchronization. Variable frequency supplied SM as the torque actuators. Power converter topologies, local current loop and the principles of  torque control. Permanent magnet servo motors with buried and surface mount magnets. Defluxing and the M-W curve in the field weakening, constant power and constant current regions. Exploitation and transient M-W characteristics of a variable frequency supplied permanent magnet SM. Fundamentals of the PMSM control, power converters, and control approaches. Fundamentals of reluctance and SR machines.
    Low frequency power transformers: Magnetic circuit, primary and secondary windings of a single-phase transformer. Electromagnetic field and the primary-to-secondary power flow. Equivalent circuit, magnetizing and leakage inductance calculation for a given magnetic circuit, airgap and the inter-winding spacing. Noload and short circuit test. Problems of electrical insulation and the heat removal. Parallel operation of power transformers. Power transformers for the use in conjunction with power converters: sensitivity to DC offset and the high frequency ripple. Auto-transformers. Three phase power transformer basics.
    Fundamentals of electric energy generation, transmission and distribution.  Water turbines, hydro power plant elements, operation and characteristics. Steam turbines and thermal power plants. Wind power and alternative energy sources. Transformation and AC power transmission. Long distance transmission problems and high voltage DC power lines. Basic (P-f and U-Q) control loops. Control, measurement and protection equipment at the power plants, transformer and converter stations. Basic information on the electric energy distribution and the trends in power consumption.