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Q1. | A squirrel cage induction motor is not favoured when ____ is the main consideration. |

A. | initial cost [Wrong Answer] |

B. | maintenance cost [Wrong Answer] |

C. | high starting torque [Correct Answer] |

D. | higher efficiency and higher power factor [Wrong Answer] |

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Explanation:-
Answer : CDiscuss it below :!! OOPS Login [Click here] is required to post your answer/resultHelp other students, write article, leave your comments |

**Also Read Similar Questions Below :**

⇒ A leading pf load on an alternator implies that its voltage regulation shall be

positive.

negative.

zero.

any one of these.

⇒ Plugging of dc machine is normally executed by

reversing the field polarity.

reversing the armature polarity.

reversing both field and armature polarity.

connecting the resistance across armature terminals.

⇒ For the parallel operation of transformers, which of the following conditions must be satisfied?

Same voltage ratios.

Must be connected in proper polarities.

R

_{e}/X

_{e}ratio should be the same.

Same kVA rating.

⇒ The resultant voltage acting across the armature circuit of a synchronous motor (E

_{r}) is the of induced emf in the armature circuit (E

_{b}) and supply voltage V.

arithmetic sum.

arithmetic difference.

phasor difference.

phasor sum.

⇒ If two induction motors A and B are identical except that the airgap of motor 'A' is 50% greater than that of motor 'B' then

the no-load power factor of A will be better than that of B.

the no-load power factor of A will be poorer than that of B.

the core losses of A will be more than those of B.

the operating flux of A will be smaller than that of B.

⇒ The de motor that draws almost same power atdifferent loads is

cumulative compound.

differential compound.

series.

shunt.

⇒ Switched reluctance motor means

salient pole synchronous motor without excitation winding

a stepper motor with salient poles

synchronous motor with salient poles on stator and rotor.

a stepper motor with closed loop control and with rotor position sensor

⇒ If two sinusoids of the same frequency but of different amplitudes and phase difference are added, the resultant is a

sinusoid of the same frequency.

sinusoid of double the original frequency.

sinusoid of half the original frequency.

non-sinusoid.

⇒ Larger diameter salient pole rotors have shorter axial length because

it occupies much less space.

it saves lot of copper in stator winding.

it reduces weight of the rotor.

number of conductors held in large circumference of rotor is very large and so they need not be long.

⇒ In a dc shunt motor, the three point starter

limits the starting current to a safer value.

provides overload protection.

provides no-volt protection.

all of the above

⇒ A dc series motor is best suited for driving

line shafting, blowers and fans.

machine tools.

shear and punches.

cranes and hoists

⇒ What is the effect of the field failure of salient pole synchronous motor connected with infinite bus?

Reduce motor torque and speed.

Not charge motor torque and speed.

Stop the motor.

Reduce motor torque but motor will continue to run at synchronous speed.

⇒ Cascade method of speed control involves the use of two coupled induction motors. The necessary condition for speed control is that

both the motors are of the wound rotor type having the same number of poles

both the motors are of the squirrel cage rotor type having different number of poles

one motor is of the slip-ring type but both the motors have the same number of poles

one motor is of the slip-ring type and the two motors have different number of poles.

⇒ Voltage control in a rotary convertor is affected by

introducing series reactance in supply leads.

induction regulator.

varying field excitation.

varying resistance in the circuit.

⇒ The repulsion start induction motor has the advantage(s) of

high starting torque (2.5 to 4.5 times of full-load torque).

low starting current (about 3.5 times of full-load current).

low cost, high efficiency and good power factor.

both (a) and (b).

⇒ The armature shaft must be able to withstand

any unbalanced magnetic pull on the armature core.

twisting strains due to transmission of torque.

bending moment due to weight of the armature and commutator.

all of the above.

⇒ The speed of a slip-ring three phase induction motor can he controlled from the rotor side by

changing the supply voltage.

changing the supply frequency.

rheostatic control.

changing the number of poles

⇒ Which of the following statement(s) associated with installation and preventive maintenance of dc machines is incorrect ?

Accumulation of carbon dust on the commutator surface may result in flash-over

The commutator should be lubricated in order to reduce brush friction

Accumulation of dust on the machine may result in overheating of the machine

Sufficient space is necessary all around the motor for movement of operational and maintenance personnels

⇒ Possible three-to-three phase transformer connection for parallel operation is

Δ-Y to Δ-Y

Δ-Δ to Δ-Y

Y-Y to Δ-Y

Δ-Y to Y-Δ

⇒ The direction of rotation of a 3-phase induction motor is clockwise when it is supplied with 3-phase sinusoidal voltage having phase sequence A-B-C. For counterclockwise rotation of the motor, the phase sequence of the power supply should be

B-C-A

C-A-B

A-C-B

B-C-A and C-A-B

⇒ In a lap wound dc generator having P poles and Z conductors the maximum number of equalizer rings will be

Z/P

2Z/P

Z/2P

Z/4P

⇒ Open-circuit test in a transformer is performed with

rated transformer voltage.

rated transformer current

direct current

high frequency supply

⇒ The Fourier series expansion of an even periods function contains

only cosine terms.

cosine terms and a constant.

only sine terms.

sine terms and a constant.

⇒ In induction machines, it is usually a standard practiceto employ

integral-slot winding with full pitch coils.

integral slots winding with chorded coils.

fractional slot winding with fractional pitch coils.

fractional slot winding with lull pitch coils.

⇒ A circuit component that opposes the change in circuit voltage is

resistance.

capacitance.

inductance.

all of the above

⇒ The interpole air gap is ____that under the field poles, in dc machines.

smaller than

larger than

equal to

none of these

⇒ Single phase synchronous motors

are self starting motors

do not need dc excitation

operate at constant speed

are built for a wider range of output

⇒ Which of the following dc generators will be in a position to build up without any residual magnetism in the field?

Series

Shunt

Separately excited

Compound

⇒ The starting torque of a squirrel cage induction motor is

very large.

very low.

slightly more than full-load torque.

zero.

⇒ A synchronous motor operates at 0.8 pf lagging. If the field current of the motor is continuously increased

the power factor decreases upto a certain value of the field current and there-after it increases.

the armature current increases upto a certain value of the field current and thereafter it decreases.

the power factor increases opto a certain value of field current and thereafter it decreases.

the armature current decreases upto a certain value of field current and there after it increases.