1.D.C. motor is to a drive a load which is
almost nil for certain part of the load cycle and peak value for short
duration. We will select this |
| series motor |
| shunt motor |
| compound motor |
| any of the above |
|
ANSWER : : compound motor
|
| 2.Where D.C. motor of H.P. 12 or more requires frequent starting, stopping, reversing and speed control |
| drum type controller is used |
| three point starter is used |
| four point starter is used |
| all above can be used |
|
ANSWER : : drum type controller is used
|
| 3.D.C. generators are normally designed for maximum efficiency around |
| full-load |
| rated r.p.m. |
| rated voltage |
| all of the above |
|
ANSWER : : full-load
|
| 4.The purpose of retardation test on D.C. shunt machines is to find out |
| stray losses |
| eddy current losses |
| field copper losses |
| windage losses |
|
ANSWER : : stray losses
|
5.D.C. motor is to drive a load which has certain minimum value for most of the time and some peak value for short
duration. We will select the |
| series motor |
| shunt motor |
| compound motor |
| any of the above |
ANSWER : : series motor
| 6.In variable speed motor |
| a stronger commutating field is needed at low speed than at high speed |
| a weaker commutating field is needed at low speed than at high speed |
| same commutating field is needed at low speed than at high speed |
| none of the above is correct |
|
ANSWER : : a weaker commutating field is needed at low speed than at high speed
|
| 7.In the D.C. motor the iron losses occur in |
| the field |
| the armature |
| the brushes |
| the commutator |
|
ANSWER : : the armature
|
| 8.One D.C. motor drives another D.C. motor. The second D.C. motor when excited and driven |
| runs as a generator |
| does not run as a generator |
| also runs as a motor comes to stop after sometime |
| also runs as a motor comes to stop after sometime |
|
ANSWER : : runs as a generator
|
| 9.Which of the following tests will be suitable for testing two similar D.C. series motors of large capacity ? |
| Swinburne’s test |
| Hopkinson’s test |
| Field test |
| Brake test |
|
ANSWER : : Field test
|
| 10.The speed of a D.C. shunt motor is required to be more than full load speed. This is possible by |
| reducing the field current |
| decreasing the armature current |
| increasing the armature current |
| increasing the excitation current |
|
ANSWER : : reducing the field current
|
| 11.If a D.C. shunt motor is working at full load and if shunt field circuit suddenly opens |
| this will make armature to take heavy current, possibly burning it |
| this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses |
| nothing will happen to motor |
| motor will come to stop |
|
ANSWER : : this will make armature to take heavy current, possibly burning it
|
| 12.During rheostat braking of D.C. series motors |
| motor is run as a generator |
| motor is reversed in direction |
| motor is run at reduced speed |
| motor is run as a generator |
|
ANSWER : motor is run as a generator
|
| 13.Hopkinson’s test on D.C. machines is conducted at |
| no-load |
| part load |
| full-load |
| overload |
|
ANSWER : : full-load
|
| 14.The condition for maximum efficiency for a D.C. generator is |
| eddy current losses = stray losses |
| hysteresis losses = eddy current losses |
| copper losses = 0 |
| variable losses = constant losses |
|
ANSWER : : variable losses = constant losses
|
| 15.D.C. generators are installed near the load centres to reduce |
| iron losses |
| line losses |
| sparking |
| corona losses |
ANSWER : : line losses
| 16.When the armature of a D.C. motor rotates, e.m.f. induced is |
| self-induced e.m.f. |
| mutually induced e.m.f. |
| back e.m.f. |
| none of the above |
|
ANSWER : : back e.m.f.
|
| 17.Which method of braking is generally used in elevators ? |
| Plugging |
| Regenerative braking |
| Rheostatic braking |
| None of the above |
|
ANSWER : : Plugging
|
| 18.Which D.C. motor has got maximum self relieving property ? |
| Series motor |
| Shunt motor |
| Cumulatively compounded motor |
| Differentially compounded motor |
|
ANSWER : : Series motor
|
| 19.In a D.C. generator, the iron losses mainly take place in |
| yoke |
| commutator |
| armature conductors |
| armature rotor |
|
ANSWER : : armature rotor
|
|
|
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Nice documents.