Generator terminology
Generator terminology
(OP)
I am trying to differentiate between an ac generator power factor rating and the impedance of the generator to answer a specific question. If somebody is asking the impedance of a generator, what would they be looking for exactly.






RE: Generator terminology
RE: Generator terminology
There is no single "impedance" for a dynamic, non-linear system like a generator. For a single value, the most useful impedance is the sub-transient impedance (X"d).
I don't think there is much direct relationship between power factor rating and the impedance.
RE: Generator terminology
Suppose we have a 100kva generator. If we decide to rate it at 100% power factor, we must install a prime mover with a 100KW output (133 HP.)
If we decide to rate the generator at 80% power factor, the prime mover need only supply 80KW. (107 HP.)
The actual power factor depends on the load, not the generator.
respectfully
RE: Generator terminology
RE: Generator terminology
- the power factor of that generator gives an idea on how much reactive power it can produce.
- the Xd (this is, I assume, what they are really expecting when they ask for the 'impedance') gives an idea of how much reactive power it can absorb. If it is a multipole generator, you would need the Xq also.
RE: Generator terminology
Most important of the reactances, Subtransient reactance X"d, is useful to quickly find out the maximum short circuit current the generator can deliver.
For example, the maximum SCC a generator can deliver will be FLA/X"d.
A 600A rated generator with 0.15pu X"d (or 15%) will deliver 600/0.15=4000A. There are some other variables but their effect would not be significant.