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

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

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Electrical Machines
Armature reaction in a DC machine

 is in the same direction as the main poles.
  makes an angle of 90° with the main pole axis.
 is in direct opposition to the main poles.
 makes an angle with the main pole axis which is load dependent.

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