electrical

DC Generator MCQ Objective Questions and Answers Page - 5

1.
 Welding generator will have A Tap winding B Wave winding C Either lap or wave winding D None of these Answer : A Explanation :
2.
 If in a 6 pole lap wound dc machine, the air gap under each pole is not the same , this is likely to result in A Higher terminal voltage B Reduced eddy currents C Unequal currents in parallel paths D One of the above Answer : C Explanation :
3.
 The number of parallel paths for a 4-pole duplex lap winding will be A 2 B 4 C 6 D 8 Answer : D Explanation :
4.
 Minimum number of coils of r400 V , 6-pole lap connected dc machine for a maximum voltage of 15V between adjacent commutator  segments should A 80 B 160 C 200 D 400 Answer : B Explanation :
5.
 Widith of a carbon brush should be equal to A Less than the width of one commutator segment B The width of 1 to 2 commutator segments C The width of 2 to 3 commutator segments D The width of more than 3 commutator segments Answer : C Explanation :
6.
 A duplex lap winding with equalizers and even number of pairs of poles is A Doubly re-entrant and number of coils per pair of poles is an odd integer B Double re-entrant and number of coils per pair of poles is an even-integer C Singly entrant and number of coils per pair of poles is an even integer D Singly entrant and number of coils per pair of poles is an odd integer Answer : A Explanation :
7.
 Wave winding is composed of A Any odd number of conductors B Any even number of conductors C That even number which is exact multiple of poles ±2 D That even number which is exact multiple of poles Answer : C Explanation :
8.
 For a 4 pole machine wave winding  is impossible with ____armature conductors A 30 B 32 C 34 D 38 Answer : B Explanation :
9.
 In a dc machine for the same value of  $\phi$, Z and N; which one of the following statements is correct  ? A Armature emf is more with wave winding than with lap winding B Armature emf is less with wave winding than with lap winding C Armature emf depends on a whether the machine is running as a motor or a generator D Armature emf is same as long as the flux density in the air gap remains the same Answer : A Explanation :
10.
 The dummy coils in dc machines are useful to A Increase the efficiency B Improve the commutation C Reduce the cost of the machine D Maintain mechanical balance of armature Answer : D Explanation :
11.
 A cumulatively compounded dc generator is supplying 20 A at 200 V Now if the series field winding is short circuited the terminal voltage A Will remain unaltered at 200 V B Will rise to 220 V C Will shoot upto a very high value D Will become less than 200V Answer : D Explanation :
12.
 A dc generator will be flat compounded if A It terminal voltage remains constant irrespective of the load current supplied by the generator&l B Generated voltage is in proportion to load current C The generator is capable  of producing higher voltage  at light load D Terminal voltage increases slightly with the load Answer : A Explanation :
13.
 Over or under compounding of a dc generator is achieved by A Shunting more or less current from the shunt filed B Shunting more or less current from the series field C Connecting is as long shunt D Connecting it as short shunt Answer : B Explanation :
14.
 An over compounded dc generator  is supplying 800A at full load on 500 V. The resistance of each conductor is 0.02Ω. The percentage of compounding is A 1.6% B 3.2% C 6.4% D 12.8% Answer : C Explanation :
15.
 Which of the following dc generator is will be in a position to build up without any residual magnetism in the field ? A Series B Shunt C Separately excited D Compound Answer : C Explanation :
16.
 Which of the following dc generators has rising V-I characteristics ? A Series B Shunt C Compound D None Answer : A Explanation :
17.
 Which of the following dc generators will have negligible terminal voltage on no load ? A Shunt B Series C Compound D None Answer : B Explanation :
18.
 An exciter for turbo - generator is a dc generator A shunt B series C compound D separately excited Answer : A Explanation :
19.
 For a specific open –circuit voltage of a dc generator, the short circuit current will be maximum when it is A Separately excited B Shunt connected C Cumulatively compounded D Differentially compounded Answer : C Explanation :
20.
 The voltage regulation of a dc generator at full load being zero implies that the generator is A shunt connected B Differentially compounded C Cumulatively compounded D Series connected Answer : C Explanation :
21.
 The _______generator has the poorest voltage regulation A Shunt B Over compounded C Under compounded D Differential compounded Answer : D Explanation :
22.
 The voltmeter connected across a generator reads voltage same  at no load and at full load (rated) The generator is of the type A Shunt generator B Series generator C Level compound D Short shunt compound Answer : C Explanation :
23.
 A dc shunt generator when driven without connecting filed winding shows an open circuit terminal voltage of 12 V . When filed winding is connected and excited the terminal  voltage drops to ze A Filed resistance is higher than critical resistance B There is no residual magnetism in the filed circuit C Filed winding has got wrongly connected D There is a fault in armature circuit Answer : C Explanation :
24.
 The  residual magnetism of a dc shunt generator can be regained by A Connecting the shunt field to a battery B Running the generator on no load for some time C Grounding the shunt field D Reversing the direction of rotation of the generator Answer : A Explanation :
25.
 Flashing of field of dc generator means A Neutralization of residual magnetism B Creation of residual magnetism by a dc source C Increasing flux density by providing extra ampere turns in field D None of the above Answer : B Explanation :
26.
 A dc series generator is employed A As a booster to maintain constant voltage at the load end of the feeder B For supplying traction load C For supplying industrial load at constant voltage D For battery charging Answer : A Explanation :
27.
 The type of dc generator used for are welding purposes is a A Series generator B Shunt generator C Cumulatively compounded generator D Differentially compounded generator Answer : D Explanation :
28.
 The essential condition for satisfactory parallel operation of two dc generators is that they should have same A kW output rating B drooping voltage characteristics C percentage regulation D speed of operation Answer : B Explanation :
29.
 The simplest way of shifting load from one shunt generator to  the other operating in parallel is by A Adjustment of speeds B Adjustment of armature resistances C Adjustment of filed rheostats D Using equalizer connections Answer : C Explanation :
30.
 If field of one of two generators operating in parallel is made very weak, then it will A Not take any load B Take major share of load C Operate as a motor and run in the same direction D Operate as a motor and run in the opposite direction Answer : C Explanation :
31.
 If a DC generator fails to build up the probable cause could not be A Imperfect brush contact B Field resistance less than the critical resistance C No residual magnetism in the generator D Faulty shunt connections tending to reduce the residual magnetism Answer : B Explanation :
32.
 Flashing the field of DC generator means A Neutralising residual magnetism B Creating residual magnetism by a DC source C Making the magnetic losses of forces parallel D Increasing flux density by adding extra turns of windings on poles Answer : B Explanation :
33.
 The e.m.f. induced in the armature of a shunt generator is 600 V. the armature resistance is 0.1 ohm. If the armature current is 200 A, the terminal voltage will be A 640 V B 620 V C 600 V D 580 V Answer : D Explanation :
34.
 In a DC generator the critical resistance refers to the resistance of A Brushes B Field C Armature D Load Answer : B Explanation :
35.
 To achieve sparkles commutation brushes of a DC generator are rocked ahead so as to bring them A Just ahead of magnetic neutral axis B In magnetic neutral axis C Just behind the magnetic neutral axis D None of the above Answer : A Explanation :
36.
 Armature coil is short-circuited by brushes when it lies A Along neutral axis B Along field axis C In any of the above positions D In none of the above positions Answer : A Explanation :
37.
 A cumulatively compounded long shunt generator when operating as a motor would be A Cumulatively compounded long shunt B Differentially compounded long shunt C Cumulatively compounded short shunt D Differentially compounded short shunt Answer : B Explanation :
38.
 To avoid formation of grooves in the commutator of a DC machine A The brushes of opposite polarity should track each other B The brushes of same polarity should track each other C Brush position has no effect on the commutator grooving D None of the above Answer : A Explanation :
39.
 The following constitute short-circuit in the armature winding. A Insulation failure between two commutator bars B Insulation failure between two turns of a coil C Two of more turns of the same coil getting grounded D All of the above Answer : D Explanation :
40.
 Number of tapings for each equalizer ring is equal to A Number of pole pairs B Number of poles C Number of parallel paths D Number of commutator segments Answer : A Explanation :
41.
 A DC generator can be considered as A Rectifier B Prime-mover C Rotating amplifier D Power pump Answer : C Explanation :
42.
 In any rotating machine that part which houses the conductors and in which e.m.f. induced is to be utilised is called A Rotor B Stator C Field D Armature Answer : D Explanation :
43.
 In a DC machine stray loss is the sum of A Total copper loss and mechanical loss B Armature copper loss and iron loss C Shunt field copper loss and mechanical loss D Iron loss and mechanical loss Answer : D Explanation :
44.
 Lap winding is compound of A Any even number of conductors B Any odd number of conductors C That even number which is exact multiple of poles +2 D That even number which is exact multiple of poles Answer : A Explanation :
45.
 In a DC generator in case the resistance of the field winding is increased, then output voltage will A Increase B Decrease C Remain unaffected D Fluctuate heavily Answer : A Explanation :
46.
 An exciter for a turbo generator is a A Separately excited generator B Shunt generator C Series generator D Compound generator Answer : B Explanation :
47.
 In case of a flat compounded generator A Voltage generated is less than the rated voltage B Generated voltage is proportional to the load on the generator C Voltage remains constant irrespective of the load D Speed varies in proportion to the load on the generator Answer : C Explanation :
48.
 Which of the following generator will have negligible terminal voltage while running on no-load? A Series generator B Shunt generator C Compound generator D Separately excited generator Answer : A Explanation :
49.
 Which of the following DC generators will be in a position to build up without any residual magnetism in the poles? A Series generator B Shunt generator C Compound generator D None of the above Answer : D Explanation :