Electrical Drives And Controls Set 13

Mechanical Engineering

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This set of Electrical Drives and Controls EDC Multiple Choice Questions & Answers (MCQs) focuses on Electrical Drives And Controls Set 13

Q1 | Why does DC motor sometimes run too fast when under-loaded?
  • due to weak field
  • due to high line voltage
  • due to brush-shifted to neutral
  • all of the mentioned
Answer: due to weak field
Q2 | Concentrated winding differ from distributed winding with the concern of
  • identical magnetic axis
  • two magnetic axis
  • no magnetic axis
  • physical spacing
Answer: identical magnetic axis
Q3 | DC machines have                  windings and synchronous machines use              windings.
  • closed,open
  • open, closed
  • open, open
  • closed, closed
Answer: closed,open
Q4 | We can place closed windings in
  • ac commutator machine
  • stepper motor
  • ac machine
  • dc machine
Answer: ac commutator machine
Q5 | Which of the following machines can be used to place open slot winding?
  • ac machine
  • ac commutator machine, ac machine
  • dc machines
  • all of the mentioned
Answer: ac machine
Q6 | The simplex lap winding has the range of winding pitch of                    
  • (-2,2)
  • (-1,1)
  • more than 2
  • less than 1
Answer: (-2,2)
Q7 | The commutator pitch for a simplex lap winding is equal to                    
  • 1 and -1
  • 1
  • -1
  • 2 to -2
Answer: 1 and -1
Q8 | A 200V dc machine has 4 poles and 40 coils, having simplex lap winding. The number of commutator segments which required in the given machine will be?
  • 40
  • 20
  • 80
  • 26
Answer: 40
Q9 | Commutator segments in a DC shunt machine is equal to the number of                    
  • coil sides
  • turns
  • coils
  • slots
Answer: coil sides
Q10 | We can employ dummy coils in a DC machine to                    
  • compensate reactance voltage
  • reduce armature reaction
  • provide mechanical balance to the armature
  • improve the waveforms generated inside the commutator
Answer: compensate reactance voltage
Q11 | In AC machines we should prefer double layer winding over single layer windings because                    
  • it requires identical coils
  • it is economical to use
  • it offers lower leakage reactance
  • all of the mentioned
Answer: it requires identical coils
Q12 | For an electrical machine with C number of coils and P poles, the distance between the coils connected by an equalizer ring is?
  • c/p
  • c/2
  • 2c/p
  • c/2p
Answer: 2c/p
Q13 | With a P-pole DC machine with armature current Ia, the current per brush arm for a lap connected windings is?
  • ia/p
  • ia/2p
  • 2ia/p
  • ia/4p
Answer: 2ia/p
Q14 | While doing regular checks on the dc machine with the lap connected winding, it is reported to have ammeter fluctuations, this can be due to                    
  • different air gaps under poles
  • variable reluctances in the core
  • irregular design deformations
  • all of the mentioned
Answer: all of the mentioned
Q15 | A 6-pole lap wound DC generator has a developed power of P watts and brush voltage of E volts. Three adjacent brushes of the machine had been found worn out and got open circuited. If the machine is operated with the remaining brushes, voltage and power that could be obtained from the machine are                    
  • e, p
  • e, 2p/3
  • e/p, 2p/3
  • e, p/3
Answer: e, p
Q16 | 1 = 0.0917.
  • reduce armature voltage
  • increase armature voltage
  • increase field current
  • decrease field current
Answer: reduce armature voltage
Q17 | Ward Leonard method is                                                        
  • armature control method
  • field control method
  • combination of armature control method and field control method
  • totally different from armature and field control method
Answer: combination of armature control method and field control method
Q18 | Reducing the field current will give us
  • constant torque and variable power speed control
  • constant torque speed control
  • variable power speed control
  • constant power speed control
Answer: constant torque speed control
Q19 | Speed-power characteristic for Ward Leonard speed control method
  • will start from origin
  • will start from some positive value on power axis
  • will start from some positive value on speed axis
  • depends on other parameters
Answer: will start from origin
Q20 | Efficiency of Ward Leonard method is
  • higher than rheostatic control method but lower than shunted field control method
  • lower than rheostatic control method
  • higher than rheostatic control method and shunted field control method
  • depends on load
Answer: higher than rheostatic control method and shunted field control method
Q21 | Ward Leonard method is an ideal choice for motor which undergoes frequent starting, stopping, speed reversal.
  • true
  • false
Answer: true
Q22 | Starting gear used in Ward Leonard method                       
  • is of small size
  • is of large size
  • size depends on application
  • is absent
Answer: is absent
Q23 | To get the speed of DC motor below the normal speed without wastage of electrical energy we use                                      
  • ward leonard control
  • rheostatic control
  • any of the ward leonard or rheostatic method can be used
  • not possible
Answer: ward leonard control
Q24 | Speed control by Ward Leonard method, can give uniform speed variation
  • in both directions
  • in one direction
  • below normal speed only
  • above normal speed only.
Answer: in both directions
Q25 | The disadvantage of the Ward Leonard control method is                        
  • high initial cost
  • high maintenance cost
  • low efficiency at high loads
  • high cost, high maintenance and low efficiency
Answer: high cost, high maintenance and low efficiency
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