Electrotechnics

Lectures:

Calculation of single- and three-phase networks (2.5 lectures)

The consumer positive direction system. Currents and voltages of single-phase systems (Time functions and phasors). Power definitions of a single-phase system (voltage-current phasor and power of different types of consumers). Symmetrical three-phase system (Characteristics, beneficial properties. Current and voltage relationships. Line and phase quantities, star and delta connection). Symmetrical three-phase system power expressions (Interpretation of effective and reactive power). Simple calculation examples.

Park vector, three-phase vector method (1.5 lectures)

Definition. Physical introduction. Space vector of three-phase winding. Space vector forming in a three-phase symmetrical state. Assumptions, requirements (Neglects. Spatial prescription. Prescription regarding its change over time). The three-phase vector as a transformation (Management of zero-order quantities. Composition. Formation of phase quantities, projection rule).

Transformers (3 lectures)

Introduction: Examples of iron-core and iron-free coils. Characteristics and purpose of application of transformers.

Single-phase transformers: Operating principle. The function, properties and construction of the iron core. The winding, its properties and construction. Main and stray flux. Calculation of the induced voltage, turns ratio, voltage ratio. Equivalent circuit derivation (The ideal transformer, resistances and stray reactances. Voltage equations, per-units. Elimination of the ideal transformer, voltage-constrain, law of balance of excitations, current ratio. Reduction /quantities, parameters/. Types of core loss and their modelling in the equivalent circuit. Simplified equivalent circuits). Phasor diagram: no-load and load state. The voltage change of the transformer. Transformer short circuit condition. Concept of drop

Three-phase transformers: Derivation. Connection methods (star, delta, zig-zag). Asymmetric load, unbalanced excitation, asymmetry of the voltage system. The delta-star connection as a solution. Phase rotation of 3F transformers (number of hours)

Transformer calculation examples

Creating a rotating field with a stationary coil system (1 lecture)

Magnetic fields of electric machines: stationary, pulsating and rotating fields. Creating a rotating field with a multiphase winding system. Torque generation in electromechanical converters. The frequency condition. Creating a sinusoidal field distribution. The angular velocity of the rotating field.

Asynchronous machine (2 lectures)

Satisfying the frequency condition. The structure and operating principle of an induction machine (stator, rotor, cage, slip ring. Why asynchronous? Why induction?). The concept of slip and its notable values. Operating states of the induction machine. Equivalent circuit of the induction machine (derivation from the equivalent circuit of the transformer. Consideration of the slip. Winding factor). The torque of the induction machine. Vector diagram of the induction machine. Current vector diagram (Derivation. What can be read? Power lines). Torque-speed characteristic curve. Stability. Power conditions and losses of the induction machine. Induction machine calculation examples.

Synchronous machine (2 performances)

Satisfying the frequency condition. Synchronous machine structure and operating principle (Design and power supply of individual parts. Cylindrical and silent-pole designs. Starting motors. Synchronization of generators. Applications). Equivalent circuit and operation of a synchronous machine (Derivation of the equivalent circuit. Meaning of the parameters. Order of magnitude of the parameters). Vector diagram of a synchronous machine (motor, generator, underexcited, overexcited, no-load, loaded cases, neglecting resistance). Synchronous generator load pick-up (Reactive power production with increased excitation. Active power production intervened from the shaft side). Synchronous machine torque. Synchronous machine stability. No-load and short-circuit measurement of synchronous machine. Synchronous machine calculation examples. Synchronous machine motor applications

Frequency converter drives (1 lecture)

Induction machine speed control options. Ensuring a constant flux with variable frequency power supply (U/f). The necessity of field weakening at speeds higher than nominal (Effect of field weakening on load capacity in terms of torque. Development of speed-torque characteristic curves). System design, selection (For application. Cooling). The intermediate DC circular frequency converter (Structure. Operation. Simple (six-step) control. ISZM (PWM) modulation. Output voltage vectors)

DC machine (1 lecture)

Satisfying the frequency condition. Construction and design of a DC machine (Poles. Armature. Commutator). Equivalent circuit of a DC machine. Calculation of the induced voltage. Calculation of torque. DC machine excitation methods. Characteristic curves of a DC machine. Options for changing the speed of DC machines.

Introduction into the “classic” electrotechnics (2 lectures)

Introduction, overview of the main fields of electrotechnics, representation how further fields are connecting to the mainstream, starting from the “classic” electrotechnics. Requirements of sustainable development. Electrotechnical application of alternative energies. Electric vehicles with alternative energy sources. New materials and technologies in the electrotechnics. Environment friendly and energy saving electrotechnics. Electrotechnical application of superconductors.

Basics of EMC. Biological effects of electricity. (1 lecture)

Basics of electromagnetic compatibility (EMC). Low- and high frequency inference, electrostatic discharge, electromagnetic impulses. Biological effects. Interactions of natural and technical environment.

Basics of protection against electric shock, electric and electrostatic discharges. (1 lecture)

Basics of protection of life against electricity. Methods against electric shock protection.

Limits and requirements. Basics of electric life protecting and safety systems. Measurements in life protection.

Basics of insulation engineering (1 lecture)

Most important properties of insulators applied in electrotechnics and electrical power networks. Physical description, basics of application and design.

Live line maintenance (1 lecture)

Technologies necessary for continuous electric power service. Technologies and working methods of live line maintenance.

Basics of building electricity (1 lecture)

Building management systems and electrical systems of buildings. Operating principles of low voltage and extre low voltage parts.

Laboratory exercises:

Examination of high voltage discharges. (Ionisation processes in gas discharges. Characteristics of breakdown voltage in gases. Breakdown in gases in practice.)

Measurements in the protection against electric shock. (Biological effects, possible cases of shock, protective methods.)

Testing the operation of the transformer. (Resistance measurement. Ratio measurement, testing the number of hours. No-load measurement. Short-circuit measurement. Load measurement)

Examination of the operating principle of electric rotating machines.

(Creating a rotating magnetic field with different arrangements. Braking with a permanent magnet. Measuring a DC machine. Reading and interpreting the name-plate data)

Examination of starting methods of electric motors. (Direct start. Star-Delta start. Soft start. Frequency converter start)