Electrical Machines
Direct-on-line (DOL) starters are not suitable for starting large DC motors, because

 the motor may not start.
 the motor may run away.
 the starting current will be enormously high.
 the starting torque becomes low.

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Electrical Machines
The 3 - Φ induction motors are, by a very considerable margin, the most widely used AC motors as

  they are capable of operation under range of leading and lagging pf.
  they have maximum efficiency and maximum starting torque.
  these are cheaper in cost, simple and rugged in construction.
  they have very good speed regulation.

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Electrical Machines
In a DC machine the armature mmf is

  stationary with respect to armature.
  stationary with respect to field poles.
 rotating with respect to field poles.
  rotating with respect to field poles as well as armature.

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