DC motor – back emf – torque equation – numerical problems Classification of DC motors – steady-state equations – numerical problems Characteristics of DC motors – numerical problems
Starting of DC motors – 3-point starter
Braking – regenerative braking, dynamic braking and plugging (concepts only)
Speed control of DC shunt and series motors – field control and armature control – numerical problems
Power flow diagram – losses and efficiency – numerical problems
Testing - Swinburne’s test – Hopkinson’s test – retardation test - separation of rotational losses - numerical problems
Single phase transformers – constructional details - principle of operation - EMF equation - ideal and practical transformer – numerical problems Operation on no load and on load - phasor diagram at different load conditions - equivalent circuit - voltage regulation – numerical problems Losses and efficiency - condition for maximum efficiency – numerical problems Testing of transformers - polarity test - OC test, SC test -
Autotransformer – saving of copper – numerical problems
3- phase transformer – construction - different connections of 3-phase transformers - Υ-Υ, Δ-Δ, Υ-Δ, Δ-Υ – numerical problems
Difference between power transformer and distribution transformer – all- day efficiency – numerical problems
Scott connection for 3-phase to 2-phase conversion Vector groupings – Yy0, Dd0, Yd1, Yd11, Dy1, Dy11
Parallel operation of 1-phase and 3-phase transformers - essential and desirable conditions
On load and off-load tap-changers
