Short Circuit test on Sync Generator.

[G_Ahmed]

I have a question regarding the short circuit test that is done on generators. While performing the short circuit test, we short the phases, I want know why doesn't it destroy the generator, we are literally creating a three phase bolted short circuit.

 

[thermionic1]

You manually control the excitation so that the output voltage is very low.

 

[FreddyNurk]

waross or catserveng would be able to confirm this as I've never actually done it, but I understand same technique can be used to dry out alternators. From what I can gather: short the windings, slowly adjust excitation so that desired current is flowing, and periodically shut down and take insulation resistance readings. The I2R heats the windings and slowly dries them out.

EDMS Australia

 

[catserveng]

Take a look at this link,

https://www.theengineeringknowledge...-short-circuit-test-of-synchronous-generator/

I have done a similar technique on several generators in the field to dry out windings after a field cleaning, but in those cases we only applied enough field current to get the windings warm. The procedure used is pretty much how Freddy has described it above.

Hope that helps, MikeL.

 

[Hoxton]

Generator standards ((IEC etc) require them to be designed and constructed to withstand a sudden three phase short circuit across the generator terminals.

This is the worst case they will see in service as downstream faults will not be as severa as the fault current will be limited by system impedance.

This test is not performed on every generator manufactured as it is stressful and takes time to arrange. It is not a test normally performed in the field.

The decrement curve of current decay can be used to determine generator reactance (sub-transient, transient etc)

 

[G_Ahmed]

Thank you very much everyone for your valuable responses.
Much Appreciated.

 

[cranky108]

The one time I saw this test done, people forgot that oil was used on something during the rewinding. So the heat of the test caused the oil to smoke out.
Some people very nervous.