Electrical Drives and Controls (EDC) MCQs | Page - 4

Dear candidates you will find MCQ questions of Electrical Drives and Controls (EDC) here. Learn these questions and prepare yourself for coming examinations and interviews. You can check the right answer of any question by clicking on any option or by clicking view answer button.

📊 Electrical Drives and Controls (EDC)
Q. The no load current of the transformer is very less due to
  • (A) mutual flux having low reluctance iron core
  • (B) mutual flux having high reluctance iron core
  • (C) leakage flux having low reluctance iron core
  • (D) leakage flux having high reluctance iron core
💬 Discuss
✅ Correct Answer: (A) mutual flux having low reluctance iron core

Explanation: it is due to the low reluctance path, the flux requirement is low in the transformer.

📊 Electrical Drives and Controls (EDC)
Q. The no load current of the induction motor is high due to
  • (A) long and high reluctance path between stator and rotor
  • (B) mutual flux having moderate reluctance path between stator and rotor
  • (C) leakage flux having low reluctance iron core
  • (D) leakage flux having high reluctance iron core
💬 Discuss
✅ Correct Answer: (A) long and high reluctance path between stator and rotor

Explanation: it is due to the higher

📊 Electrical Drives and Controls (EDC)
Q. Mechanically air gaps in induction motor are kept very low to avoid
  • (A) lower power factor
  • (B) lagging nature
  • (C) magnetizing current
  • (D) all of the mentioned
💬 Discuss
✅ Correct Answer: (D) all of the mentioned

Explanation: air gap is kept lower to avoid the low value power factor, lagging behaviour and to reduce the magnetizing current.

📊 Electrical Drives and Controls (EDC)
Q. The low no load power factor
  • (A) reduces full load operating pf
  • (B) increases full load operating pf
  • (C) reduces full load excitation voltage
  • (D) increases full load excitation voltage
💬 Discuss
✅ Correct Answer: (A) reduces full load operating pf

Explanation: the low no-load power factor reduces full load operating pf.

📊 Electrical Drives and Controls (EDC)
Q. 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
  • (A) locking
  • (B) plumming
  • (C) crawling
  • (D) cogging
💬 Discuss
✅ Correct Answer: (C) crawling

Explanation: running stably at low speed around 1/7th of normal motor speed is known as crawling.

📊 Electrical Drives and Controls (EDC)
Q. The great advantage of the double squirrel-cage induction motor over single cage rotor is that its
  • (A) efficiency is higher
  • (B) power factor is higher
  • (C) slip is larger
  • (D) starting current is lower
💬 Discuss
✅ Correct Answer: (D) starting current is lower

Explanation: the outer cage has higher resistance and low reactance while vice versa for the inner cage. so at starting the current is confined to outer cage with the reduction in starting current improving the torque.

📊 Electrical Drives and Controls (EDC)
Q. 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
  • (A) speed of air gap field w.r.t. stator is ns-nr anticlockwise
  • (B) speed of air gap field w.r.t. stator is ns-nr clockwise
  • (C) speed of airgap field w.r.t rotor is ns clockwise
  • (D) speed of airgap field w.r.t. stator is ns-nr clockwise
💬 Discuss
✅ Correct Answer: (A) speed of air gap field w.r.t. stator is ns-nr anticlockwise

Explanation: the air gap field of stator = - (ns-nr).

📊 Electrical Drives and Controls (EDC)
Q. (II) If a large 3–phase squirrel-cage induction motor with no load is started at full voltage, it will be damaged.
  • (A) i is true, ii is false
  • (B) i is true and ii is also true
  • (C) i is false, ii is true
  • (D) i and ii are false
💬 Discuss
✅ Correct Answer: (A) i is true, ii is false

Explanation: large current of short duration are not harmful to induction motor but it may cause voltage drop in the power supply.

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