Induction Motors and AC Machines

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Questions and Answers

What is the main reason for keeping the air gap as small as possible in a three-phase induction machine?

  • To increase the magnetizing current
  • To keep the magnetizing current low (correct)
  • To increase the power consumption
  • To reduce the starting torque

What is the purpose of the slots in the stator of a three-phase induction machine?

  • To accommodate the three-phase windings (correct)
  • To reduce the number of phases
  • To increase the air gap
  • To accommodate the rotor

What is the name of the part of the induction machine that rotates?

  • Stator
  • Air gap
  • Rotor (correct)
  • Magnetizing current

What is the main advantage of using power electronic converters as a supply source for an induction machine?

<p>To augment the characteristics of the machine (D)</p> Signup and view all the answers

What is the primary reason for the widespread use of induction machines in industries and household applications?

<p>They offer several advantages, including being cheap and rugged (D)</p> Signup and view all the answers

What is the percentage of total electrical energy generated that is consumed by induction machinery?

<p>60% (B)</p> Signup and view all the answers

What is unique about the starting process of an induction machine?

<p>It is self-starting (B)</p> Signup and view all the answers

What is the characteristic of an induction machine that allows it to run at almost constant speed from no-load to full-load condition?

<p>It is maintenance-free (C)</p> Signup and view all the answers

What is the purpose of short-circuiting the rotor winding through external resistance?

<p>To improve the performance of the motor (C)</p> Signup and view all the answers

What type of machine is used for high-power applications (MW range)?

<p>Wound rotor induction motor (D)</p> Signup and view all the answers

What is the purpose of the three copper rings called 'slip rings' on the rotor shaft?

<p>To connect the rotor winding to the external resistance (B)</p> Signup and view all the answers

What is the spatial phase difference between the three-phase stator windings?

<p>120∘ (A)</p> Signup and view all the answers

What is the principle of operation of a three-phase induction motor based on?

<p>Faraday's law of electromagnetic induction (D)</p> Signup and view all the answers

What is the result of supplying a balanced three-phase supply to a three-phase stator winding?

<p>A rotating magnetic field (B)</p> Signup and view all the answers

What is the requirement for the rotor winding in a wound rotor induction motor?

<p>It should be short-circuited (D)</p> Signup and view all the answers

What is the application of a wound rotor induction motor in wind energy generation?

<p>As a generator (B)</p> Signup and view all the answers

What are the two types of rotor structures?

<p>Squirrel cage and slip ring (C)</p> Signup and view all the answers

What are the slots in the stator lamination used for?

<p>To accommodate three-phase windings (A)</p> Signup and view all the answers

What is the advantage of using open slots in stator design?

<p>Lower leakage reactance (C)</p> Signup and view all the answers

What is the shape of the squirrel cage rotor?

<p>Skewed (D)</p> Signup and view all the answers

What is the purpose of the end rings in a squirrel cage rotor?

<p>To short the copper or aluminum bars (D)</p> Signup and view all the answers

What is the characteristic of the construction of a squirrel cage rotor?

<p>Rugged and strong, requiring no maintenance (C)</p> Signup and view all the answers

What is the similarity between a wound rotor and a stator?

<p>Both have three-phase windings (C)</p> Signup and view all the answers

How are the three-phase windings in a stator connected?

<p>Either in star or in delta (C)</p> Signup and view all the answers

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