Electrical Machine - II (3150910) MCQs

MCQs of Induction Machines

Showing 61 to 70 out of 95 Questions
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61.

The main reasons for unbalanced current in the stator winding of three-phase induction motor is/are

(a)

Unbalance in number of turns, placement of the winding, and winding resistance
(b)

Unbalance supply Voltage
(c)

Unbalance impedance of the stator or rotor winding
(d)

All of these 
Answer:

Option (d)

62.

Which of the following is/are present in an unbalanced system?

(a)

Positive sequence component
(b)

Negative sequence component
(c)

Zero sequence component
(d)

Positive, Negative, & Zero sequence component
Answer:

Option (d)

63.

The negative sequence has the phase sequence just __________ to positive sequence, hence __________________  produced in opposite direction.

(a)

opposite,    Voltage
(b)

same,     Torque
(c)

opposite,    Voltage & Current 
(d)

opposite,    Voltage, Current & Torque 
Answer:

Option (d)

64.

Temperature rise and load carrying capacity of the three-phase induction motor will _________ & _________ respectively with increase in Voltage unbalance.

(a)

Decrease & Increase
(b)

Increase & Increase
(c)

Decrease & Decrease
(d)

Increase & Decrease
Answer:

Option (d)

65.

Effective motor torque of the three-phase induction motor will _________  with an increase in Voltage unbalance.

(a)

Decrease
(b)

 Increase
(c)

Remains the same
(d)

Cant say anything using only this data
Answer:

Option (a)

66.

Protecting devices selected for one set of unbalanced conditions maybe ___________ for a different set of unbalanced voltages.

(a)

inadequate
(b)

adequate
(c)

Perfectly
(d)

Cant say anything using only this data
Answer:

Option (a)

67.

The operation of a motor with _________ unbalance condition is not recommended, and will probably result in damage to the motor. 

(a)

above a 10%
(b)

above a 7.5%
(c)

above a 5%
(d)

above a 15%
Answer:

Option (c)

68.

An R-L series circuit consisting of constant reactance (X) but variable resistance (R), the locus of the __________ is a __________. 

(a)

Frequency, Circle
(b)

Voltage, Circle
(c)

Current,   Circle
(d)

Current, Parabola
Answer:

Option (c)

69.

In the equation of current, 𝑰 = (𝑽/𝑿)×𝒔𝒊𝒏⁡∅.   𝑽/𝑿 = ___________  &  𝒔𝒊𝒏⁡∅ = ___________ 

(a)

power factor angle   &   diameter of the circle
(b)

diameter of the circle   &   power factor angle  
(c)

Impedance   &   power factor angle  
(d)

power factor angle   &   Impedance 
Answer:

Option (b)

70.

Why locus of the current did not start from the origin (where X and Y-axis start) in the case of circle diagram of a three-phase induction motor?

(a)

due to stator and rotor copper loss
(b)

because its rotating device
(c)

even at no load. IM draw the No-Load Current (Io) due to Mechanical Losses And Iron Losses
(d)

None of these 
Answer:

Option (c)

Showing 61 to 70 out of 95 Questions
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