Electrical Machines
Satisfactory commutation of DC machine requires

All of these
 brushes should smoothly run in the holders.
 smooth, concentric commutator properly undercut.
 brushes should be of proper grade and size.

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Electrical Machines
For a single phase capacitor start induction motor which of the following is valid?

 Direction of rotation cannot be changed.
  Rotation can be changed by reversing main winding terminals.
 Rotation can be changed by interchanging supply terminals.
 None of these.

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Electrical Machines
In synchronous generator, inverted V curve is drawn between

 field current on X-axis and armature current on Y-axis
 field current on Y-axis and armature current on X-axis
 field current on Y-axis and power factor on X-axis
 field current on X-axis and power factor on Y-axis

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