I’ve been fighting this all summer and it is getting worse. It started off randomly running more often without overheating to now randomly overheating more often than running.It's all about heat. Or, rather, it's all about cooling (the removal of heat from the generator). Heat is the worst enemy of synchronous generators. To produce a lagging power factor of 0.8 it's necessary to increase excitation being applied to the generator rotor--one of the hardest areas to cool in a generator.
A generator--ANY generator---can produce a LOT more energy than it's rated at, just not for long periods of time. Why? Because the increased power production leads to more amperes flowing in the generator's stator AND rotor and if that heat can't be "removed" or cooled then the insulation of the windings in the stator and/or the rotor is going to be damaged which is going to lead to tripping and failure.
The reason most generators are rated at 0.8 pf (lagging) is convention. Even if the load(s) are mostly inductive in nature any single generator on a power system/grid can be operated at 1.0 pf (unity power factor). In that case, that generator is not producing or sharing in the supply of VArs to the power system/grid.
The subject of VArs has been covered many times before on Control.com. It's yet another subject that has a lot of myths and wive's tales associated with it. It also has many ways to describe it--mathematically and graphically. Most importantly, VArs don't have any tangible effects that can be measured, like torque and horsepower and watts do. In my opinion starting any discussion of VArs with formulas or tangents or vectors and triangles doesn't do much to explain the effect of VArs--which is what synchronous generators are often used to do: Counter the effects of inductive loads (and sometimes capacitive loads depending on the nature of the loads) on the power system/grid. (And to counter the effects of VArs it's necessary to either "over-excite" or "under-excite" the generator, and the effects of either of those conditions MUST BE taken into account when operating the generator. That's the main purpose of generator reactive capability curves--to understand what the limits of operating a particular generator are so as not to overheat the generator and damage its windings.)
Anyway, generator ratings DO NOT MEAN that generators MUST BE operated at those values--not at all!!! It just says that the generator can safely and continually be operated at those values without causing damage to the generator (because of the heat produced at those values). A turbine also has a nameplate--and quite often, turbines aren't operated continuously at those numbers (Base Load, or even Peak Load or Peak Reserve Load). The nameplate just says the turbine can be safely and optimally operated for long periods of time at that load under those conditions. Same as the generator nameplate--safe and continual operation at those loads under those conditions.
A LOT of people think that a generator has to always be operated at nameplate rating (particularly power factor)--and that's just not true. In fact, if you look at and analyze a GE-design heavy duty gas turbine's nameplate with the nameplate of the generator it drives you will see that the generator is rated for MORE than the turbine, almost always. Why? Because under some ambient conditions (cold inlet air temperatures, primarily) the turbine power output will exceed the turbine nameplate and if the generator were rated the same as the turbine then it would be necessary to limit turbine output to protect the generator from overheating. Or, if the generator were rated less than the turbine it would be necessary to ALWAYS limit the turbine output to protect the generator.
Rating generators at 0.8 pf (lagging) is a way of comparing different generators using the same criteria. One generator producing power at 0.8 pf (lagging) might not be able to produce the same KVA (specifically, watts/kW/MW) as a generator its being compared to. And by doing this for most all generators it provides a way of comparing "apple to apples" instead of "apples to oranges."
thank you so much for your such suggestion really appreciate that.@loribennms,
A generator is a device for converting torque to amperes. Those amperes are transmitted by wires to various locations and loads which then, mostly, convert them back to torque or some useful work (yes; even TV can be useful, as can YouTube).
The generator (the thing that produces the amperes and volts) has to be driven by a prime mover (as they are typically called). In your case the prime mover is some kind of reciprocating engine that has a cooling system. Other prime movers are steam turbines, wind turbines, hydro turbines and combustion (gas) turbines.
The original poster of this thread was asking about the how the rating of the generator (the thing that produces the amperes and volts) is determined. Your problem was with the prime mover cooling system--NOT the generator.
Your question would have been better to have been posted as a new thread/post, not as a response to this thread--as it is not related to the problem you are experiencing.
Yes; if you are flushing the cooling system of a reciprocating engine-driven generator set (genset) with the thermostat installed in the system you are not going to get a very good cooling system flush. The thermostat can be removed temporarily for the flush, and then reinstalled apartments for sale in baabda--usually without too much effort and only a new gasket (if that).
Best of luck in getting your "generator" cooling system training record signed off.
by Seth Price
by Seth Price
by Gunner Scott