Review of basics of DC machines, classification of DC generator, types of armature winding, EMF equation, no-load characteristic, armature reaction, load characteristics. Commutation,types of Commutation, commutation difficulties, interpoles, compensating winding and equalizer rings (only qualitative treatment).
(a) Classification, Back EMF and its significance, Torque equation, Characteristics of shunt,series & compound motors, speed control of shunt, series and compound motors.Application of motors. DC motor starters (b) Special DC motors- permanent magnet motors,brushless DC motors.Applications.
LOSSES AND EFFICIENCY- Losses in DC machines, power flow diagram, efficiency, condition for maximum efficiency. TESTING OF DC MACHINES- Direct & indirect methods of testing of DC machines-Brake test, Swinburn’s test, Hopkinson’s test, Retardation test, Field’s test, merits and demerits of tests.
Basic principle of operation, construction of salient & non-salient pole synchronous machines, generated EMF, effect of distribution and chording of winding, harmonics-causes,reduction and elimination. Armature reaction, synchronous reactance, leakage reactance, phasor diagram of non salient type alternator.
Voltage regulation by EMF, MMF, ZPF & ASA method.Schort circuit ratio and its importance.Two reaction theory-direct and quadrature axis reactances,phasor diagram.Slip test and regulation.
Synchronizing to infinite bus bars, parallel operation of alternators. Operating characteristics, power angle characteristics excluding armature resistance, operation for fixed input and variable excitation, power flow equations including armature resistance, capability curves of synchronous generators.
Principle of operation, phasor diagrams, torque and torque angle, Blondal diagram, effect of change in load, effect of change in excitation, V and inverted V curves. Synchronous condensor, hunting and damping. Methods of starting synchronous motors.