Top 150+ Solved Design of Electrical Machines MCQ Questions Answer
Q. Which ofthe following materials is used in the manufacture of resistance grids to beused in the starters of large motors ?
a. Copper
b. Aluminium
c. Steel
d. Cast-iron
Q. Materials exhibiting zero value of resistivity are known as ______ .
a. conductors
b. semiconductors
c. insulators
d. superconductors
Q. ________ has a lowrelative permeability and is used principally in field frames when costis of primary importance and extra weight is not objectionable.
a. Cast steel
b. Aluminium
c. Soft steel
d. Cast iron
Q. ______is extensively used for those portions of magnetic circuit which carry steady fluxand need superior mechanical properties ?
a. Grey cast-iron
b. Cast steel
c. High carbon steel
d. Stainless steel
Q. The heated parts of an electrical machine dissipate heat into their surroundings bywhich of the following modes of heat dissipation ?
a. Conduction
b. Convection
c. Radiation
d. All ofthe above
Q. The heat dissipated by from a surface depends upon its temperature and itscharacteristics like colour, roughness etc.
a. conduction
b. convection
c. radiation
d. any ofthe above
Q. The mcrease in heat dissipation by air blasts is due to increase in
a. conduction
b. convection
c. radiation
d. any ofthe above
Q. On which of the following variables heat convected depends ?
a. Power density
b. Temperature difference between heated surface and coolant
c. Thermal resistivity, density, specific heat
d. All ofthe above
Q. Which ofthe following methods is used for air cooling of turbo-alternators ?
a. One sided axial ventilation
b. Two sided axial ventilation
c. Multiple inlet system
d. All ofthe above
Q. Multiple inlet system of air cooling of turbo-alternators can be used for machines ofrating upto
a. 10 MW
b. 30 MW
c. 60 MW
d. 150 MW
Q. Which ofthe following is an advantage of hydrogen cooling ?
a. Increase in efficiency
b. Increase in ratings
c. Increase in life
d. All ofthe above