Get more KW out of generators

As the value of VAR decreases, PF increases, with PF ideal = 1.0. Now as PF starts to exceeed about 0.9 ish, the amount of capacitance required to further correct the PF increases, and above around 0.95-0.98 greatly increases, making any further savings very small (compared to the cost of all those capacitors). Working thru the KVAR sizing formula and capacitor price lists will show this. This means that you only want to correct the PF up to a certain point to obtain a good cost/benefit balance.

As a side note, the main grid power system will not work if PF = 1.0 = ideal as some value of VAR is required to give some capacity to the network (whose power levels are constantly changing), or it will all fall over the moment the load changes.

My customer generates about 10MW, but the local utility company wants a 90% power factor. Therefore he has his generator compensate for the vars needed. I need to know if he can get more than 10MW out of the generator, or use less fuel, if he stops generating about 5MVARS and installs 5MVARS instead. Thanks.

Wow. Running a generator just to make up VARs? What a waste! He would be better served by converting one or more of his biggest motor loads to synchronous and running them as synchronous condensers, but capacitors would be the next best thing. From your nickname I woul;d say you have a vested interest in the capacitor route.

Yes I do have a vested interest in that I would design and sell the capacitor bank(s), but the payback has to be there. The utility penalty is not enough to support the project and I don't want to project anything else saved without support. I'm hoping I can find some testimonials out there of facilities that quit generating KVAR and put in capacitors. What were the savings in extra KW generated or fuel saved? Anyone?

hi Capbob

Is there alot of heavy DC loads like big motors,an outfit call Ross Hill makes a rather interesting power factor correcter. But on there instalations there is usually a minimum of 10 traction motors rated at a 1000 hp plus, with the addition of the Power factor corrector they can run on 2 engines rather then 3.

Scott

I will check out Ross Hill, thanks. This installation doesn't have motors over 1000hp, just the turbines. I did correct a saw mill running 3-1000KW diesel generators. After correction they only needed two running. The fuel saved paid for the capacitors in two months, but they were not connected to the grid. If they were, I assume they could have sold KW or just saved the fuel. The facility I want to correct now uses natural gas turbines and are connected to the grid. Thanks again.

Unless there is an existing large synchronous motor installed that was sized larger than is needed for the mechanical load, it may prove to more economical to use a percentage of the installed generator's capacity to produce the VARS than to replace an existing large induction motor with a new oversized synchronous one. It would probably depend on the plant's life expectancy as to which would be the most economical.