Question 1

Which of the following is the basic consideration in the design of insulation ?

Accepted Answer

A) Electrical considerations 
B) Mechanical considerations 
C) Thermal considerations 
D) All of the above

Question 2

________ is the common method of applying brushes to the commntator.

Accepted Answer

A) Radial 
B) Trailing 
C) Reaction 
D) All of the above

Question 3

The high voltage winding is usually which of the following type ?

Accepted Answer

A) Cylindrical winding with circular conductors 
B) Cross-over winding with either circular or small rectangular conductors 
C) Continuous disc type winding with rectangular conductors 
D) All of the above types

Question 4

Which of the following brushes can be used for high values of current density ?

Accepted Answer

A) Metal graphite brushes 
B) Hard carbon brushes 
C) Electro-graphitic brushes 
D) Natural graphite brushes

Question 5

Which of the following problem arises in D.C. motors which are fed from thyristor bridge circuits ?

Accepted Answer

A) Increased I R losses 
B) Increased core losses 
C) Poor commutation 
D) All of the above

Question 6

The laminations of the armature of a D.C. machine are usually _____ thick.

Accepted Answer

A) 0.1 to 0.2 mm 
B) 0.2 to 0.3 mm 
C) 0.3 to 0.4 mm 
D) 0.4 to 0.5 mm

Question 7

is usually used for brush rockers

Accepted Answer

A) Mild steel 
B) Copper 
C) Aluminium 
D) Cast-iron

Exam 4: Design and Operation of DC Machines