Test: Basic Concept of Rotating Electrical Machines of Electrical Machines- 2

Question 1

A 6-pole machine is rotating at a speed of 1200 rpm. This speed in electrical radians per sec and mechanical radian per sec are respectively given by

Accepted Answer

120π, 40π

Answer

60&pi;, 20&pi;

Answer

40π/3, 40π

Answer

40π, 120π

Question 2

In an alternator, frequency per revolution is equal to

Accepted Answer

number of pole-pairs

Answer

speed in rps

Answer

twice the number of poles

Answer

number of poles

Question 3

A three - phase alternator is wound with a 60 degree phase spread armature winding and develops 300 kVA. If the armature is reconnected utilizing all the coils for single-phase operation with a phase spread of 180 degree, the new rating of the machine will be

Accepted Answer

200 kVA

Answer

300 kVA

Answer

100 kVA

Answer

250 kVA

Question 4

A synchronous machine has full-pitch coils having coil-span of 12 slots. For eliminating third harmonic, the coil-span should be

Accepted Answer

8 slots

Answer

10 slots

Answer

9 slots

Answer

6 slots

Question 5

The 5^th harmonic mmf wave, produced by 3-phase currents flowing in 3-phase balanced winding, rotates w.r.t fundamental field (N_s = speed of fundamental mmf wave) at a speed of

Accepted Answer

Answer

Answer

Answer

Question 6

Match List- I (Power losses) with List - II (Dependent upon) and select the correct answer using the codes given below the lists:
List-I
A. Stray load loss
B. Brush constant loss
C. Hysteresis loss
D. No-load rotational loss
List-Il
1. Load
2. Value of flux
3. Rotor rotation
4. Square of load
Codes:
A B C D
(a) 3 1 4 2
(b) 4 1 2 3
(c) 3 4 2 1
(d) 4 1 3 2

Accepted Answer

(b)

Answer

(a)

Answer

(c)

Answer

(d)

Question 7

Output rating of
1. dc generators is in kVA.
2. ac motor is in kW.
3. ac generator is in kVA.
4. dc motors is in kW.
5. induction motors is in h.p.
6. synchronous motors is in kVA.
From these, the correct statements are:

Accepted Answer

2, 3 and 4

Answer

1, 3, 4 and 5

Answer

1, 4 and 5

Answer

2, 3, 5 and 6

Question 8

If P_i be the iron loss and P₀ be the ohmic ioss on full load, then which of the following conditions has to be satisfied to obtain maximum efficiency at 2/3 full load?

Accepted Answer

Answer

Answer

Answer

Question 9

If ϕ_m is the maximum value of flux due to any one phase, the resultant flux in 3-phase and 2-phase ac machines would be given by

Accepted Answer

1.5 ϕ_m, and ϕ_m; both rotating

Answer

2 ϕ_m and 1.5 ϕ_m; both rotating

Answer

1.5 ϕ_m, rotating and ϕ_m, standstill

Answer

1.5 ϕ_m, and ϕ_m; both standstill

Question 10

Resistance of one conductor for a dc machine is 10 mΩ. What would be the armature circuit resistance if the dc machine with 640 conductors and 8 poles is wave-connected ?

Accepted Answer

1.6&Omega;

Answer

3.2&Omega;

Answer

2.4&Omega;

Answer

1.2&Omega;

Question 11

A 6-pole, 50 Hz, 3-phase induction motor has a stator bore diameter of 1.2 meters, its stator is cut and laid out flat, so that rotating mmf wave now becomes a travelling mmf wave. What is the linear velocity of the travelling mmf wave in meters per second ?

Accepted Answer

62.8

Answer

56.6

Answer

36.4

Answer

None of these

Question 12

Assertion (A) : In a rotating electrical machine, having 2 poles on the stator and 4 poles on the rotor, the net electromagnetic torque developed is zero.
Reason (R) : In all rotating electrical machines, the number of rotor poles must be equal to the number of stator poles for development of electromagnetic torque.

Accepted Answer

Both A and R are true and R is a correct explanation of A.

Answer

Both A and R are true but R is not a correct explanation of A.

Answer

A is true but R is false.

Answer

A is false but R is true.

Question 13

Assertion (A) : Exciting winding is one which produces working flux.
Reason (R) : Armature winding in one in which the working emf is induced by the working flux,

Accepted Answer

Both A and R are true and R is a correct explanation of A.

Answer

Both A and R are true but R is not a correct explanation of A.

Answer

A is true but R is false.

Answer

A is false but R is true.

Question 14

Assertion (A) : At the time of winding design of three-phase alternators, the attention is mainly directed for the attenuation of triplen harmonics, by adopting a chording angle of 60° electrical.
Reason (R): Three-phase alternators are invariably star-connected to eliminate triplen harmonics from the line e.m.f.

Accepted Answer

A is false but R is true.

Answer

Both A and R are true and R is a correct explanation of A,

Answer

Both A and R are true but R is not a correct explanation of A.

Answer

A is true but R is false.

Question 15

The induced emf in the armature conductors of a d.c motor is

Accepted Answer

sinusoidal

Answer

trapezoidal

Answer

rectangular

Answer

alternating

Basic Concept of Rotating Electrical Machines Machines- 2 - Free MCQ Practice

MCQ Practice Test & Solutions: Test: Basic Concept of Rotating Electrical Machines of Electrical Machines- 2 (15 Questions)

A 6-pole machine is rotating at a speed of 1200 rpm. This speed in electrical radians per sec and mechanical radian per sec are respectively given by

In an alternator, frequency per revolution is equal to

A three - phase alternator is wound with a 60 degree phase spread armature winding and develops 300 kVA. If the armature is reconnected utilizing all the coils for single-phase operation with a phase spread of 180 degree, the new rating of the machine will be

A synchronous machine has full-pitch coils having coil-span of 12 slots. For eliminating third harmonic, the coil-span should be

The 5^th harmonic mmf wave, produced by 3-phase currents flowing in 3-phase balanced winding, rotates w.r.t fundamental field (N_s = speed of fundamental mmf wave) at a speed of

Output rating of
1. dc generators is in kVA.
2. ac motor is in kW.
3. ac generator is in kVA.
4. dc motors is in kW.
5. induction motors is in h.p.
6. synchronous motors is in kVA.
From these, the correct statements are:

If P_i be the iron loss and P₀ be the ohmic ioss on full load, then which of the following conditions has to be satisfied to obtain maximum efficiency at 2/3 full load?

If ϕ_m is the maximum value of flux due to any one phase, the resultant flux in 3-phase and 2-phase ac machines would be given by

Resistance of one conductor for a dc machine is 10 mΩ. What would be the armature circuit resistance if the dc machine with 640 conductors and 8 poles is wave-connected ?

A 6-pole, 50 Hz, 3-phase induction motor has a stator bore diameter of 1.2 meters, its stator is cut and laid out flat, so that rotating mmf wave now becomes a travelling mmf wave. What is the linear velocity of the travelling mmf wave in meters per second ?

Assertion (A) : Exciting winding is one which produces working flux.
Reason (R) : Armature winding in one in which the working emf is induced by the working flux,

The induced emf in the armature conductors of a d.c motor is

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Basic Concept of Rotating Electrical Machines Machines- 2 - Free MCQ Practice

MCQ Practice Test & Solutions: Test: Basic Concept of Rotating Electrical Machines of Electrical Machines- 2 (15 Questions)

A 6-pole machine is rotating at a speed of 1200 rpm. This speed in electrical radians per sec and mechanical radian per sec are respectively given by

In an alternator, frequency per revolution is equal to

A three - phase alternator is wound with a 60 degree phase spread armature winding and develops 300 kVA. If the armature is reconnected utilizing all the coils for single-phase operation with a phase spread of 180 degree, the new rating of the machine will be

A synchronous machine has full-pitch coils having coil-span of 12 slots. For eliminating third harmonic, the coil-span should be

The 5th harmonic mmf wave, produced by 3-phase currents flowing in 3-phase balanced winding, rotates w.r.t fundamental field (Ns = speed of fundamental mmf wave) at a speed of

Output rating of 1. dc generators is in kVA. 2. ac motor is in kW. 3. ac generator is in kVA. 4. dc motors is in kW. 5. induction motors is in h.p. 6. synchronous motors is in kVA. From these, the correct statements are:

If Pi be the iron loss and P0 be the ohmic ioss on full load, then which of the following conditions has to be satisfied to obtain maximum efficiency at 2/3 full load?

If ϕm is the maximum value of flux due to any one phase, the resultant flux in 3-phase and 2-phase ac machines would be given by

Resistance of one conductor for a dc machine is 10 mΩ. What would be the armature circuit resistance if the dc machine with 640 conductors and 8 poles is wave-connected ?

A 6-pole, 50 Hz, 3-phase induction motor has a stator bore diameter of 1.2 meters, its stator is cut and laid out flat, so that rotating mmf wave now becomes a travelling mmf wave. What is the linear velocity of the travelling mmf wave in meters per second ?

Assertion (A) : Exciting winding is one which produces working flux. Reason (R) : Armature winding in one in which the working emf is induced by the working flux,

The induced emf in the armature conductors of a d.c motor is

Topicwise Question Bank for Electrical Engineering

Topicwise Question Bank for Electrical Engineering

Top Courses for Electrical Engineering (EE)

About this Electrical Engineering (EE) Practice Test

Explore more Electrical Engineering (EE) Study Resources

The 5^th harmonic mmf wave, produced by 3-phase currents flowing in 3-phase balanced winding, rotates w.r.t fundamental field (N_s = speed of fundamental mmf wave) at a speed of

Output rating of
1. dc generators is in kVA.
2. ac motor is in kW.
3. ac generator is in kVA.
4. dc motors is in kW.
5. induction motors is in h.p.
6. synchronous motors is in kVA.
From these, the correct statements are:

If P_i be the iron loss and P₀ be the ohmic ioss on full load, then which of the following conditions has to be satisfied to obtain maximum efficiency at 2/3 full load?

If ϕ_m is the maximum value of flux due to any one phase, the resultant flux in 3-phase and 2-phase ac machines would be given by

Assertion (A) : Exciting winding is one which produces working flux.
Reason (R) : Armature winding in one in which the working emf is induced by the working flux,