Electrical Drives And Controls Set 5

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This set of Electrical Drives and Controls EDC Multiple Choice Questions & Answers (MCQs) focuses on Electrical Drives And Controls Set 5

Q1 | The effect of fringing increases as we
  • increase air gap
  • decrease air gap
  • increase in flux density
  • introduce more ferric core material
Q2 | is  
  • main field distortion
  • shift in mna
  • reduction in main field
  • none of the mentioned
Q3 | If the students give a forward shift of 10° to the dc generator, then it  
  • reduces flux per pole
  • improves flux per pole
  • increases the flux density in core
  • none of the mentioned
Q4 | A dc machine is run at rated speed in forward direction and then in backward direction. It is observed that, speeds of the rotation are different, then it leads to the conclusion of  
  • incorrect brush placement
  • incorrect pole and core alignment
  • incorrect field supply
  • all of the mentioned
Q5 | For a dc machine, its commutator has a diameter of 50 c rotating at 1000 rpm. For a brush width of 1 cm, the time commutation taken by the machine will be  
  • 0.382 ms
  • 0.456 ms
  • 0.573 ms
  • 0.312 ms
Q6 | An induction motor can be said analogous to  
  • transformer
  • synchronous motor
  • universal motor
  • stepper motor
Q7 | A 3-phase induction motor with its rotor blocked behaves similar to a  
  • transformer under short circuit of secondary terminals
  • transformer under open circuit of secondary
  • synchronous motor under slip test
  • synchronous motor under open circuit
Q8 | No load current in induction motor is 10- 20% of full load current and the no load current of transformer is 2-6%.
  • true
  • false
Q9 | no load estimated current for the machine?
  • 12 a
  • 20 a
  • 30 a
  • 5 a
Q10 | The no load current of the transformer is very less due to  
  • mutual flux having low reluctance iron core
  • mutual flux having high reluctance iron core
  • leakage flux having low reluctance iron core
  • leakage flux having high reluctance iron core
Q11 | The no load current of the induction motor is high due to  
  • long and high reluctance path between stator and rotor
  • mutual flux having moderate reluctance path between stator and rotor
  • leakage flux having low reluctance iron core
  • leakage flux having high reluctance iron core
Q12 | At no load induction motor has possible power factor as  
  • 0.2
  • 0.5
  • 0.65
Q13 | Mechanically air gaps in induction motor are kept very low to avoid  
  • lower power factor
  • lagging nature
  • magnetizing current
  • all of the mentioned
Q14 | The low no load power factor  
  • reduces full load operating pf
  • increases full load operating pf
  • reduces full load excitation voltage
  • increases full load excitation voltage
Q15 | An induction motor when started on load, it does not accelerate up to full speed but runs at 1/7th of the rated speed. The motor is said to be  
  • locking
  • plumming
  • crawling
  • cogging
Q16 | The great advantage of the double squirrel-cage induction motor over single cage rotor is that its  
  • efficiency is higher
  • power factor is higher
  • slip is larger
  • starting current is lower
Q17 | The rotor of 3-phase slip ring induction motor is fed from a 3-phase supply with its stator winding short circuited having rotor rotating clockwise at a speed of Nr, then the
  • speed of air gap field w.r.t. stator is ns-nr anticlockwise
  • speed of air gap field w.r.t. stator is ns-nr clockwise
  • speed of airgap field w.r.t rotor is ns clockwise
  • speed of airgap field w.r.t. stator is ns-nr clockwise
Q18 | (II) If a large 3–phase squirrel-cage induction motor with no load is started at full voltage, it will be damaged.
  • i is true, ii is false
  • i is true and ii is also true
  • i is false, ii is true
  • i and ii are false
Q19 | The PWM control of DC motor varies
  • linearly with speed
  • inversely with speed
  • parabolically with speed
  • exponentially with speed
Q20 | Ward-Leonard system of system of speed control is not recommended for  
  • constant speed operation
  • wide speed
  • frequent-motor reversed
  • very slow speed
Q21 | Mark the wrong option. Which of the following cause and effect behaviour in speed control is correct when field resistance is increased.
  • decrease in flux
  • increase in armature current
  • increase in emf
  • decrease in speed
Q22 | resistance will  
  • decrease the speed of motor
  • increase the speed of motor
  • not have signicant effect on speed
  • no effect
Q23 | by  
  • armature voltage control
  • field resistance control
  • any of the methods
  • none of the mentioned
Q24 | must be ensured that  
  • it is used on separately excited machine
  • it is used on shunt machine
  • it is used on series machine
  • any of the mentioned machine
Q25 | works well for speed  
  • below, above
  • above, below
  • base speed.