Electrical Engineering Technology II

Course Content

Module Content

Machines and Utilisation II: Three – Phase Transformer; description of the construction of the three phase transformer: primary windings, secondary windings, Iron – core (core type and shell type). explanation of the principle of operation of three phase transformer, current, voltage, turns, relationship between primary and secondary values, transformer e.m.f. equation. description of three phase transformer connections, star delta, delta star, delta – delta, Star – star. explanation of three phase transformer characteristics, transformer on lead, resistive loading, capacitive loading, inductive loading, transformer efficiency test, open circuit test and short circuit test, transformer losses, iron losses, copper – losses, statement of application of three phase transformer, step up three phase load, step down three phase load. solution of problems on three phase transformers, ratios, losses.

Special Motors; description of construction of the following special motors: stepper motors, permanent magnet d.c. motor, low inertia d.c. motors, permanent magnet synchronous motor, switched reluctance motor, servomotors (DC/AC). explanation of principle of operation of, stepper motors, permanent magnet d.c. motors, low inertia d.c. motors, permanent magnet synchronous motor, switched reluctance motors, servomotors (AC/DC). statement of application of the mentioned special motors.

Electrical Machines Installation and Commissioning; explanation of electrical machines installation procedures ,installation manual, requirements (materials etc.), unpacking, visual inspection for completeness and damage, explanation of mounting procedures: mountings, foundations, alignments, assembly test to be carried out(winding test, functional test, test – run)commissioning procedures, completeness, functionability, spares availability, manuals, correct specifications, correct assembly.

Electrical Machine Rewinding; need for rewinding: burnt-out windings, non operation according to specification. Material/equipment for rewinding, wire and wire sizes, insulators (types, sizes, varnish), equipment (hot air blower, hot air oven, former, counter etc.), aspects of rewinding(machine preparation, collection of equipment and materials, coils). procedure for machine rewinding, preparations (coils, slots), insertion of coils, connection of the coils, testing of windings (continuity, Insulation, Short circuit), varnishing/curing, assembly/inventing, final tests (functional, current balance, polarity).

Maintenance of Electrical Machines; operations and care of the following test instruments, insulation, resistance tester (megger), continuity tester (lamp, bell, ohmmeter), multimeter (voltage/current). common faults in electrical machines: short circuit, Open circuit, earth faults, leakages, breakages, misalignments.

Aprocedure for fault diagnosis in electrical machines: check continuity of the windings, check the insulation (earth leakage of the windings), check for open circuit, check the alignments, belts, bearings and mountings. describe maintenance and repair procedure: lubrication of bearings and moving parts, alignments, mountings, dusting, lightening of loose mechanical/electrical parts.

Practicum

Three Phase Transformer; connecting three phase transformer to determine operation
principles, performing load tests on three phase transformer. Electrical Machine
Installation and Commissioning; general requirements for installation sites, Electrical
machine inspection; visual inspection, completeness of parts, electrical machine
installation, assembly, wiring. Electrical machine alignment; test to confirm operation,
Test to confirm machine specifications (current r.p.m.),functional test on newly installed
electrical machine, manuals, visual inspection, completeness of parts. Electrical machine
rewinding; assembling tools, equipment and materials for rewinding, preparation of
cores, removal of old windings, cleaning of core, correct rewinding: preparation of coils,
inspection of coils, insulation, termination, varnishing, testing. functional test after
rewinding: operation characteristics. Electric machine maintenance; handling and usage
of various instruments to locate faults in electric machines, various instrument (multi
meter, insulation tester, continuity tester), maintenance and repair of electrical machines,
diagnose faults, repair, carryout tests (insulation resistance, continuity, leakage, functional
test).