Electrical Drives And Controls Set 10

Mechanical Engineering

Practice Mode Previous Next
On This Page

This set of Electrical Drives and Controls EDC Multiple Choice Questions & Answers (MCQs) focuses on Electrical Drives And Controls Set 10

Q1 | Which of the following is correct formula for braking torque in plugging?
  • n (ka2/rb)
  • n2 (ka2/rb)
  • n-1 (ka2/rb)
  • (ka2/rb)
Answer: n (ka2/rb)
Q2 | Electrical braking of any variety becomes less effective as                                  
  • speed increases
  • speed decreases
  • independent of speed
  • depends on supply voltage
Answer: speed decreases
Q3 | Plugging is applied in a motor, if we don’t make the switch OFF what will happen?
  • motor will come to rest as a result of plugging
  • motor will come to rest and will start rotating in another direction
  • motor will burn
  • nothing will happen
Answer: motor will come to rest and will start rotating in another direction
Q4 | Plugging is used in                          
  • small motors only
  • small and medium powered
  • only in large heavy machines
  • everywhere
Answer: small motors only
Q5 | Which of the following is dynamic braking?
  • reversal of field connections
  • reversal of armature connections
  • addition of equal and opposite field
  • removal of armature circuit from current machine circuit
Answer: removal of armature circuit from current machine circuit
Q6 | Braking time in the dynamic braking is the function of                            
  • system inertia
  • load torque
  • motor rating
  • all- system inertia, load torque and motor rating
Answer: all- system inertia, load torque and motor rating
Q7 | In dynamic braking, when braking is applied system acts as                        
  • freely running machine
  • motor with slow speed
  • generator
  • motor with same speed in opposite direction
Answer: generator
Q8 | In which of the following electrical braking method, energy is supplied back to the supply?
  • plugging
  • dynamic braking
  • regenerative braking
  • in all electrical braking
Answer: regenerative braking
Q9 | What will happen if DC shunt motor is connected across AC supply?
  • will run at normal speed
  • will not run
  • will run at lower speed
  • burn due to heat produced in the field winding
Answer: burn due to heat produced in the field winding
Q10 | What will happen if the back emf of a DC motor vanishes suddenly?
  • the motor will stop
  • the motor will continue to run
  • the armature may burn
  • the motor will run noisy
Answer: the armature may burn
Q11 | What will happen, with the increase in speed of a DC motor?
  • back emf increase but line current falls.
  • back emf falls and line current increase.
  • both back emf as well as line current increase.
  • both back emf as well as line current fall.
Answer: back emf increase but line current falls.
Q12 | In DC motor, which of the following part can sustain the maximum temperature rise?
  • field winding
  • commutator
  • slip rings
  • armature winding
Answer: field winding
Q13 | Direction of rotation of motor is determined by                          
  • faraday’s law
  • lenz’s law
  • coulomb’s law
  • fleming’s left-hand rule
Answer: fleming’s left-hand rule
Q14 | Which power is mentioned on a name plate of a motor?
  • gross power
  • power drawn in kva
  • power drawn in kw
  • output power available at the shaft
Answer: output power available at the shaft
Q15 | An electric motor is having constant output power. So, motor will have a torque speed characteristic                                                
  • circle about the origin.
  • straight line parallel to the speed axis.
  • straight line through the origin.
  • rectangular hyperbola
Answer: rectangular hyperbola
Q16 | In which of the following case we will get maximum power?
  • ea = 2 x supply voltage
  • ea = supply voltage
  • supply voltage = 2 x ea
  • supply voltage = 4 x ea
Answer: supply voltage = 2 x ea
Q17 | Sometimes motor has to be de-rated.
  • true
  • false
Answer: true
Q18 | The armature shaft of a DC motor must be able to withstand                              
  • bending moment due to weight of the armature.
  • any unbalanced magnetic pull on the armature core.
  • twisting stains due to transmission of torque.
  • bending moment, unbalanced magnetic pull and twisting stains
Answer: bending moment, unbalanced magnetic pull and twisting stains
Q19 | In DC machines the residual magnetism is present. The order of residual magnetism is
  • 2 to 3 per cent
  • 10 to 15 per cent
  • 20 to 25 per cent
  • 50 to 75 per cent
Answer: 2 to 3 per cent
Q20 | Sparking is discouraged in a DC motor.
  • true
  • false
Answer: false
Q21 | How many steps are involved in the construction of single phase induction motor?
  • 3
  • 4
  • 5
  • 6
Answer: 5
Q22 | What is the lamination used for the stator?
  • cast iron
  • die cast aluminium alloy frame
  • cast iron or die cast aluminium alloy frame
  • cast iron and die cast aluminium alloy frame
Answer: cast iron or die cast aluminium alloy frame
Q23 | What type of coils are used for winding the single phase induction motor generally?
  • rectangular coils
  • square coils
  • cruciform coils
  • circular coils
Answer: circular coils
Q24 | How many kinds of single phase windings are present?
  • 2
  • 3
  • 4
  • 5
Answer: 3
Q25 | How are the poles and pitches in the concentric windings?
  • single pole, different pitches
  • different pole, different pitches
  • different pole, single pitch
  • single pole, single pitch
Answer: single pole, different pitches
Previous Next