Generator field winding inductance 1

[n1mr0d]

Hi,

What are typical inductance & resistance values of generator field windings? Do these values change during operation?

 

[Skogsgurra]

Can not say what a typical resistance or inductance is. It depends a lot of what machine we are talking about.

But there are some standard assumptions you can use.

First. The resistance can be calculated from excitation voltage and excitation current. Let's say 300 V and 600 A for a synchronous motor. That means that the resistance is 500 milliohms.

Second. Typical time constants are in the 1 - 3 seconds range. Sometimes more. Since time constant is L/R, you can calculate L from T*R. If the time constant is 3 seconds, you get L = 3*0.5 = 1.5 henry in the example above.

Resistance changes with temperature - the change is around 0.4 percent/degree C. The inductance does not change with temperature - at least not so much that you need to take it into account.

Gunnar Englund

http://www.gke.org

 

[davidbeach]

Anderson's Analysis of Faulted Power Systems (at home, I'm not) has a table of typical PU values for various generators. The physical units will vary as the rating, but the PU values will be more stable across a range of ratings.