Electrical Machines
When R2 is rotor resistance, X2 the rotor reactance at supply frequency and s the slip, then the condition for maximum torque under running condition will be

  R2 = s2X2.
  R2 = s2X2.
  sR2 = X2.
  R2 = sX2.

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Electrical Machines
A compound dc generator is delivering full load current at a terminal voltage of 230 V. Its series-field winding gets short circuited. If its terminal voltage 1. becomes more than 230 V, it is overcompounded generator 2. becomes more than 230 V, it is differentially compounded generator 3. becomes less than 230 V, it is overcompounded generator 4. becomes less than 230 V, it is differentially compounded generator 5. becomes less than 230 V, it is level compounded generator From these, the correct answer is

 1, 4, 5
 2,3
 1, 4
 2, 3, 5

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Electrical Machines
In a DC machine the armature mmf is

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

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

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

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Electrical Machines
Which of the following is done in speed control of DC motor by field flux control?

 Inserting resistance to armature circuit and field circuit.
 Inserting an additional resistance in the armature circuit.
 Any of above.
 Inserting an additional resistance in the field circuit.

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