Parallel operation of DC Shunt Generator

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Parallel operation of DC Shunt generator

Parallel operation of DC shunt generator is similar to the operation of two storage batteries in parallel.

  • In the case of generators we can alter the external characteristics easily while it is not possible with batteries.
  • Before connecting the two machines the voltages of the two machines are made equal and opposing inside the loop formed by the two machines.
  • This avoids a circulating current between the machines. The circulating current produces power loss even when the load is not connected.
  • In the case of the loaded machine the difference in the induced emf makes the load sharing unequal.

Parallel operation of DC Shunt generator

              Characteristics of two shunt generators in Parallel

Load Sharing of Parallel Connected DC Generators

  • The load sharing between shunt generators in parallel can be easily regulated because of their drooping characteristics.
  • The load may be shifted from one generator to another merely by adjusting the field excitation. Let us discuss the load sharing of two generators which have unequal no-load voltages.
  • Let E1, E2 = no-load voltages of the two generators
  • R1, R2 = their armature resistances
  • V = common terminal voltage (Bus-bars voltage)

Then V = E1 − I1R1

= E2 − I2R2

  • Thus current output of the generators depends upon the values of E1 and E2. These values may be changed by field rheostats.
  • The common terminal bus-bar voltage will depend upon
  1. the emfs of individual generators and
  2. the total load current supplied.
  • It is generally desired to keep the bus-bars voltage constant. T

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