Why Generator is rated at 0.8 PF?
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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."
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."
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."
It a Northern Lights M673D. Here are all the things done over the summer:
A. New coolant expansion tank and heat exchanger core and rubber boots. The generator was used and sat for a couple of years. There was a lot of loose rust.
B. New thermostat.
C. New coolant pump and hose. The old passages for the temp sensor and temp switch were full of sludge.
D. New raw water impeller and stainless exhaust elbow. The old iron elbow was starting to rot out.
E. Flushed out numerous times with Prestone coolant flush and fresh water, but would never run with coolant flush longer than an hour without overheating. These flushes have always resulting in rusty colored water being drained.
I spent about 30 minutes with Northern Lights on the phone and their conclusion was the same as mine. Something in cooling passages in the engine block interrupts the flow of coolant as the genset heats up. The genset will Star warm up to about 170 on the temp gauge and then 10 minutes or so jump from 170 to more than 200 in 15 secs or less. If I didn’t catch it in time, the temp switch would shut the generator off.
One thing we both noted when flushing the system with water without running the generator, the passages immediately after the thermostat aren’t really flushed well as the water flows from the coolant tank through the hose through the water pump into the block below the thermostat. Since I have the thermostat out I am going to flush the system both statically without running the generator and then with a coolant flush. If I solve this I hope to have my generator cooling system training record signed off. If AI has a better suggestion, I am open to it.
moderators note : removed unwanted link inserted in quote
@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--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.
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--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.
A power factor of 0.8 indicates that the generator is designed to handle a mix of both inductive (like motors) and resistive (like lighting) loads efficiently.
Manufacturers typically select a power factor of 0.8 based on the industry-standard assumption that the majority of loads in practical applications are indeed inductive. This choice strikes a balance between the generator's capacity to handle reactive power (inductive loads) and real power (resistive loads) efficiently.
Manufacturers typically select a power factor of 0.8 based on the industry-standard assumption that the majority of loads in practical applications are indeed inductive. This choice strikes a balance between the generator's capacity to handle reactive power (inductive loads) and real power (resistive loads) efficiently.
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.
