Electrical Engineering Technology I

Course Content

 Module Content

Theory:

• D.C. Machines; description of the construction of d.c. machines: stator (frame, main poles, commutator), other parts e.g. brushes and brush gear, bearings. Explanation of principle of operation of d.c. machines (generator principle, motor principle, e.m.f. equation, problems solving related to e.m.f. equation), description of the classification of d.c. generators according to field connection: separately excited, self-excited (series, shunt, compound (long and short)), diagrams, problem solving related to self-excited generators, description of the characteristics of d.c. machines, generator (terminal voltage/current for series, shunt and compound lead characteristics of series, shunt and compound), motors (speed/current characteristics, torque/current characteristics, speed/torque). description of the operation of face plate starter: need for the starter, protective devices (Overload coil, No volt release coil), explanation of d.c. motor speed control (field and armature regulation, voltage variation method, electronic methods.) , explanation of d.c. motor breaking (rheostatic, plugging, regenerative), statement of the application of d.c. machine, application of d.c. generators depending on the field connection (series, shunt and compound), application of d.c. motors depending on characteristics (speed/current, torque/current and speed/torque), explanations of armature reaction and commutation in d.c. machines, armature reaction (causes, effects and methods of minimizing the effects), commutation (causes of poor commutation, effects of poor commutation, methods of improving commutation by increase of brush contact resistance, shifting brush position, commutating poles).


• A.C. Machines: Single Phase AC Motors; description of the construction of single phase a.c. motors (stator, rotor), explaining the principle of operation of single phase a.c. motors, field produced by a simple, single phase motors, creation of second rotating phase split phase (resistor, inductor), capacitor start, capacitor run, shaded pole, repulsion induction motor, universal motor, description of characteristics of single phase a.c. motors, torque/speed characteristics (split phase, capacitor start, capacitor run, shaded pole, repulsion induction, universal motor), reversing direction of rotation.


• Three phase system; principles of three phase generation, methods of three connection, line and phase quantities, calculation of three phase balance systems, methods of power measurement in three phase balance systems. Three Phase Induction Motors; description of the construction of three phase induction motor (stator ,main poles, rotor or squirrel cage and wound, explanation of the principle of operation: ( production of rotating magnetic field, production of torque, slip and slip speed, relationship between speed, number of poles and frequency, power stages and power losses, description of various motor starting methods, need, comparison of various starters, direct on line starter, star – delta starter, Auto transformer starter, Resistance starter. Description of the characteristics of three phase induction motor: torque/speed, torque/slip, torque/current, application of three phase induction motor depending on characteristics, industrial/commercial applications, domestic applications.


• Three Phase Synchronous Machines; description of the construction of three phase synchronous machine: stator, rotor (salient pole, cylindrical), explanation of principle of operation of three phase synchronous machine, not selfstarting, operates at synchronous speed only, explanation of the starting and synchronizing methods, starting methods( synchronizing conditions, lamps method i.eLamps dark method and lamps in sequence), synchroscope. explanation of characteristics of three – phase synchronous machines (Operates at constant speed, inherently not self-starting, Operates at various power factors i.e leading, unit and lagging), v-characteristics, statement of the application of three – phase synchronous machines, constant speed drives, power factor correction. solution of problems on three phase synchronous machines, power factor improvement problems.


• Industrial Drives; explanation of types of industrial drives (individual drive, group drive, multi-motor drive, power transmission i.e direct, gears, chain, belt/pulley, rope). Couplings( direct mechanical coupling, electrical coupling e.g eddy current, fluids, electric clutch), explanation of factors influencing the choice of a motor for industrial drive, electrical characteristics, starting characteristics, speed, control, braking, running characteristics. size and rating of motors, continuous, intermittent or variable load cycle. mechanical consideration, type of enclosure, noise level, type of bearings, rower transmission method, type of cooling, cost( capital cost, running cost) ,description of various types of motor enclosures (need for enclosures, open type, drip – proof, splash – proof, screen – protected, flame – proof, pipe – ventilated, totally enclosed.)


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1. Machines and Utilisation II: D.C. Machines; connection of various d.c. machines to obtain operation characteristics, separately excited, self-excited (series, shunt, compound). determination of various characteristics of d.c. machines: d.c. generators (voltage/current, load characteristics, curve plotting), d.c. motors (speed/current, torque/current, speed/torque, curve plotting).


2. A.C. Machines: Single phase A.C. motors; identification of the main parts of single phase a.c. motors, connection of circuit to demonstrate operation of single phase a.c. motor, performing experiments to plot characteristics of single phase a.c. motors. Three Phase Induction Motor; connection, starting principles, DOL starter, star/starter, resistance starter. performing load tests on three phase induction motor, connection, data recording and curve plotting: torque/speedtorque/current, efficiency.


3. Three Phase Synchronous Machine; synchronize three phase synchronous motor, synchronisation of three phase synchronous motor: lamps method (lamps dark, lamps in sequence), synchroscope method. Industrial Drives; demonstration of performance of various drives and couplings, drives (belt/pulley, gear, chain), couplings (direct mechanical, eddy current, fluid, electric clutch), dismantling and assembling various motor enclosures, drip proof, totally enclosed, flame proof, pipe/duct ventilated.