Elektricne
masine i postrojenja TE4EMP

Rezultati 2. kolokvijuma i zakljucne ocene

Zadaci i resenja na 2. kolokvijumu

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

Dodatne informacije o predmetu, uputstva za lab. vezbe, semestralni rad, projekat,

*regular subject for EL and AU
option students,*

*7th semester, 3 + 1 + 1*

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

__
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.