Electrical Machines
If the handle of a three point starter goes to back to OFF position, it may be due to

 over load.
 all of these.
 high filed circuit resistance.
 zero or very low voltage supply.

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

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