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Electrical machine design
1-Dont try to cram or spend more time here just read it fast and cover syllabus then practice MCQ's cheptor of same topic to check your progress. . |
2-Wrong options are also given but dont concentrate there, Right answer is in bold format. |
Q21 ⇒ The time taken by the machine to attain
0.632 of its final steady temperature
rise is called heating time constant [other wrong options] [Discuss in forum] cooling time constant either (a) or (b) none of the above |
Q22 ⇒ ____ electromagnets generally function
as holding magnets. Portative [other wrong options] [Discuss in forum] Tractive Either of the above None of the above |
Q23 ⇒ Power transformers have rating above 200 kVA [other wrong options] [Discuss in forum] equal to 50 kVA equal to 100 kVA none of the above |
Q24 ⇒ The heat dissipating capability of
transformers of ratings higher than 30
kVA in increased by providing which of
the following ? All of the above [other wrong options] [Discuss in forum] Corrugations Fins Tubes Radiator tanks |
Q25 ⇒ A current density of ____ is used for
large power transformers with forced
circulation of oil or with water cooling
coils 5.4 to 6.2 A/mm2 [other wrong options] [Discuss in forum] 1.5 to 2.5 A/mm2 3.5 to 4.5 A/mm2 4.0 to 5.0 A/mm2 |
Q26 ⇒ The stator of a D.C. machine comprises
of all of the above [other wrong options] [Discuss in forum] main poles interpoles frame |
Q27 ⇒ In a D.C. machine the current per brush
arm should not be more than 400 A [other wrong options] [Discuss in forum] 100 A 200 A 300 A |
Q28 ⇒ Pitch of commutator segment should
not be less than 4 mm [other wrong options] [Discuss in forum] 1 mm 2 mm 3 mm |
Q29 ⇒ The air gap of an induction motor is
made as ____ as possible. small [other wrong options] [Discuss in forum] large either of the above none of the above |
Q30 ⇒ The number of stator slots should ____
be equal to the number of rotor slots never [other wrong options] [Discuss in forum] always sometimes none of the above |
Q31 ⇒ If the frequency is changed vvithout altering
the number of poles the dispersion
co-efficient does not change [other wrong options] [Discuss in forum] changes becomes zero none of the above |
Q32 ⇒ The use of salient poles on high speed
alternators will cause excessive windage loss and excessive noise [other wrong options] [Discuss in forum] reduced windage loss with low noise reduced windage loss but excessive noise excessive windage less but reduced noise |
Q33 ⇒ A short time intermittent rating of
electric motors is considered while
slecting motors for punching machines [other wrong options] [Discuss in forum] sirens blowers reciprocating compressors |
Q34 ⇒ If an insulating material is operated
beyond the maximum allowable temperature,
its life is drastically reduced [other wrong options] [Discuss in forum] drastically increased unaffected none of the above |
Q35 ⇒ The change in flux linkages can be
caused in which of the following ways ? All of the above [other wrong options] [Discuss in forum] The flux is constant with respect to
time and is stationary and the coil
moves through it The coil is stationary with respect to flux and the flux varies in magnitude with respect to time Both the changes mentioned above occure together, i.e., the coil moves through a time varying field |
Q36 ⇒ The heat dissipated by from a surface
depends upon its temperature and
its characteristics like colour, roughness
etc. radiation [other wrong options] [Discuss in forum] conduction convection any of the above |
Q37 ⇒ With conventional hydrogen cooling it
is possible to increase the rating of a
single unit to 200 MW [other wrong options] [Discuss in forum] 50 MW 100 MW none of the above |
Q38 ⇒ In self cooled motors the cooling time
constant is about ____ than the heating
time constant because cooling conditions,
are worse at standstill. 2 to 3 times greater [other wrong options] [Discuss in forum] 3 to 4 times greater 4 to 5 times greater none of the above |
Q39 ⇒ Which of the following is the commonly
used type of electroinagnets ? All of the above [other wrong options] [Discuss in forum] Flat-faced armature type Horse shoe type Flat-faced plunger type |
Q40 ⇒ Power transformers should be designed
to have maximum efficiency at or near full load [other wrong options] [Discuss in forum] at one-fourth load at one-half load any of the above |
Or |