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Synchronous machine

  1. May 18, 2015 #1
    in a parallel operation of synchronous generators...while synchronising a new generator to a bus..why the speed of incoming generator should be slightly more than the other generators that are connected to the bus?
  2. jcsd
  3. May 18, 2015 #2
    Because as soon as the generator is connected it will take some load and will try to slow down and the already loaded gen. will try to speed up. If both had the same intial speed this will result in a phase difference after connection. A reverse current will flow into the new gen. and activate the reverse power trip.
  4. May 18, 2015 #3
    how it will cause phase difference when the speed will be same? can you please elaborate?
  5. May 18, 2015 #4


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    The speed will not be the same. When the generator is connected it will provide power to the system and the electrical counter torque on the shaft won't match the input mechanical torque. The machine will slow down. The other machine will speed up, since it takes less load now. With them running at different speeds they will be out of synch. That causes the phase difference. I didn't really add anything to the first response but I think he is pretty clear. Does it make sense?
  6. May 18, 2015 #5
    thank you..
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