Electrical Machines
A dc series motor driving and electric train faces a constant power load. It is running at rated speed and rated voltage. If the speed has to be brought down to 0.25 p.u. the supply voltage has to be approximately brought down to

  0.75 p.u
  0.125 p.u
  0.25 p.u
  0.5 p.u

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Electrical Machines
A DC shunt generator builds up to a voltage of 220 V at no load while running at its rated speed. If the speed of the generator is raised by 25% kepping the circuit conditions unaltered, then the Voltage to which the machine would build up will

 increase to 1.25 times 220 V
 increase to value lying between 220 V and 1.25 times 220 V
 not change and remain at 220 V
 increase to a value greater than 1.25 times 220 V

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