Machines VIVA ques..

EE2305-electrical machines 2 lab(viva )

MMF &EMF:

1.       adv of rotating field in alternator

2.       alterna rated in kva not in kw

3.       armature reaction in alter

4.       synchr reactance

5.       synchr impedance

6.       voltage regulation of alternator

7.       residual emf in an generator

8.       assumption made in emf

9.       adv &disadv of emf&mmf

zpf&asa:

1.       method available to reduce harmonic in alternator

2.       what is infinite bus bar

3.       why potier reactance>leakage reactance

4.       why synch mech is designed to have high ratio of armature reactance to resistance

5.       scr

6.       adv of zpf

regulation of alter by slip test:

1.       adv of salient pole synch machine

2.       on what factor xd&xq depends

3.       two reaction theory

4.       effect of saliency in narmature reaction

5.       why xd>xq

v curve& inverted v:

1.       hunting

2.       3phase syn motor fails to start-reson

3.       Syn condenser

4.       Application of syn motor

5.       Syn motor fails to develop its full torquewhy

Load test of 3phase induction motor:

1.       Why IM is called rotating transformer

2.       Why IM will never in syn speed

3.       d/b slip ring rotor &cage rotor of IM

4.       cogging of IM

5.       max.torque for 3phase IM –condition

6.       crawing of IM

7.       how swlip vary bwith load

8.       possible reson if a 3phase motor fails to start

load test on 1phase IM:

1.       not self starting –why

2.       double revolving field theory applied to 1phase Im

3.       two starting arrangements

4.       purpose of auxiliary winding

5.       function of centrifugal switch

6.       how direction of IM is reversed

7.       why it has low PF

8.       can shaded pole IM can be reversed-how

no load and blocked rotor test on 3phase IM:

1.       why IM is called asynchronous motor

2.       slip at which max.torque occure in 3phase IM

3.       reson for inserting addition resistance in rotor circuit of slip ring IM

4.       no load current of IM>equivalent transformer

5.       PF of IM is very low at starting

6.       Induction generator

7.       Mech power o/p represents in the eqe.circuit of an IM

No load &BR test on 1phase IM:

1.       Slip-totque char of 1phase Im

2.       Problems of operating DC series motor with AC supply

3.       Speed control of universal motor

4.       Adv of AC series motor

5.       Principle operation of stepper motor

6.       Appli of linear IM

Separation of no load losses:

1.       Why rotor slot of 3phase IM are skewed

2.       Purpose of end ring in squrriel cage Im

3.       Air  gap lenth is kept min. in IM,why

4.       Losses in im

How eddy current loss is minimized in I