Genset
Genset
(OP)
Is there any draw back on adding capacitors to the terminal genset with a pf of .8 to raise it to 1.
why does most manufactures use a base of .8 and not a value closer to unity
why does most manufactures use a base of .8 and not a value closer to unity





RE: Genset
Gunnar Englund
www.gke.org
RE: Genset
RE: Genset
Value of rated p.f. of 0.8(lag.) is standard for most generators. Generator with the same kW and higher p.f. (eg.0.9-1.0) could be smaller machine, but of course 'smaller' source of reactive power to the system.
RE: Genset
RE: Genset
Your generator has PF=0.8 or capacity to provide real life resistive and inductive loads like electric motors. The lower the PF the more reactive power it can supply to feed reactive loads. As it was mentioned above, the load defines the PF, not the generator.
RE: Genset
RE: Genset
The power factor is a characteristic of the load.
The manufacturers rating of 0.8 indicates the lowest power factor load that can be used on the set without derating the set.
You may add capacitors to the generator to improve the power factor of the load seen by the generator. You will reduce the generator current slightly.
As has been pointed out by TheBlacksmith, the kw rating is dependant on the size of the motor. Even if you correct the power factor you usually cannot get more kw out of the set because the engine slows down. If you have a load with a low power factor you may use capacitors to correct the power factor.
respectfully
RE: Genset
RE: Genset
I mean a generator with operating PF=1.0, I do not mean the PF in the nameplate.
RE: Genset
I was involved with a short experiment that illustrated this point.
Case; A small power plant, 2 x 600 kw gensets,plus 3 x 350 kw gensets.
The load is slightly over 600 kw and two generators are running. This is a common occurance.
The 600 kw set was rated 0.8 PF and was running close to 0.8 PF.
We think that if we correct the power factor with capacitors, we can run up to 750 kw and avoid the need for the second set.
We feel that we can safely overload the 600 kw set for a few minutes to test our theory. By adjusting the governors we start to overload the 600 kw set. At about 608 kw, the engine starts to lose speed and the frequency starts dropping.
Conclusions;
The maximum kw is determined by the power of the engine.
The engine in question was capable of producing 600 kw and no more.
A second illustration is the application of single phase generators in size ranges above about 20 kw.
At least one major gen-set manufacturer does not use single phase alternators above about 20 kw., nor do they assemble single phase sets above that size. They supply the single phase market by reconnecting and rerating three phase sets.
For example, a set may be rated at 50 KVA, 40 KW, 0.8 PF, three phase. If a single phase set is required this set may be reconnected in either zig-zag, or double delta.
The new kva rating is 2/3 of the original rating, or 33 KVA.
The same engine is used so there is enough power for 40 KW.
The new rating will be, 33 KVA, 33 KW, 1.0 PF.
respectfully