28) The speed of a d.c. shunt motor of 3 kW is 2000 r.p.m. when connected to a constant voltage supply. The speed is to be varied upto 2500 r.p.m. What speed control method is to be used ?

Increasing the back e.m.f. with a resistor

Limiting the armature current with a shunt resistor

Changing the voltage with a starter

Changing the field current by a field rheostat

Answer is:

Changing the field current by a field rheostat

50%

25%

150%

200%

Answer is:

increase by 5 percent

decrease by 5 percent

not change

infinity

Answer is:

DC differential compound motor

DC shunt motor

DC series motor

Separately excited motor

Answer is:

Differentially compounded D.C. motor

D.C. shunt motor

D.C. Series motor

Cumulatively compouned D.C. motor

Answer is: