B.Tech E & T 3rd Sem

Q.10 What are the starting methods of synchronous motor, Explain any one method.(10)GROUP C: All Questions are Compulsory.Q.11 Fill in the blanks (each question carries 2 marks)(i)(ii)(iii)(iv)(v)emf equation of alternator is ______In dc series motor torque is directly proportional to ____ of armature current.In lap winding no. of poles _____ to no. of parallel path.From short circuit test we determine _____.The efficiency of transformer is maximum when copper losses ____ to ironlosses.Q.12 Multiple choice question. (Each question carries 2 marks)](i)(ii)(iii)(iv)In a dc compound generator flat compound characteristic is obtained byconnecting variable resistance.(a) across the series field(b) in series with series field(c) in parallel with shunt field(d) in series with shunt fieldWhat are the effect of armature reaction(a) cross magnetizing(b) magnetizing(c) de-magnetizing(d) all of abovesmaller air gap in polyphase I.M. helps to(a) reduce the chances of crawling(b) increase starting torque(c) reduce chance of logging(d) reduce magnetizing currentThe dummy coils in DC machine are useful to(a) increase efficiency(b) imprese commutation(c) reduce cost of machine (d) none of above(v)Direction of dc series motor can be changed(a) by interchanging supply terminal(b) by interchanging field terminal(c) either changing supply terminal or interchanging field terminals(d) by interchanging supply terminal as well as field terminalQ.13 True or false (each question carries 1 mark).(i) The synchronous reactance is reactance due to armature reaction of machine(ii) In full pitch coil the coil span and pole pitch are equal(iii) The maximum torque will depend on rotor resistance(iv) The use of higher fluse density in the transformer design increase weight perKVA.(v) The power factor of a synchronous motor is independent of its excitation.