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Could you expand on how an imbalanced load affects fuel efficiency?
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Scoobyshep
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As a generator is loaded the engine has to work harder to fight the magnetic flux. If you load 1 leg (or 2 legs) the engine is working harder to keep up. Now the unbalanced part, the unbalanced current returns to the source (generator head) via the neutral (its being wasted and not performing any useful work).
Mathematically (using a single phase in the example for easier math) if you have 2 120 volt loads 1 50 amp and 1 20 amp on separate phases there is a 30 amp unbalance which is being directed back to the head. The engine is working hard enough to keep that 50 amp load up. Now if the loads were balanced there would be an even 35 amps on each leg, so the engine would have to only work at keeping 35 amps of field going. Same amount of work being done but the engine isnt working as hard.
Make sense?
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Why is energy on the neutral not performing work?
Scoobyshep
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Because its energy returning to the head. In a balanced environment the neutral is carrying 0 amps each leg acts as the return for the other (essentially these are now 2 120 volt devices wired in series) all energy created is being turned into useful work. When there is an imbalance the current carried by the neutral is not going through the other leg and being wasted
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Doesn't all energy that leaves the head have to return to it?
Scoobyshep
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Yes, the difference being returning to the head through the other leg or through the neutral.
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I fell like I should probably let you off the hook at this point.
I was asking those questions to make the point that the return path doesn't matter in regards to fuel efficiency or energy waste. The engine won't be loaded any differently whether a 5kw load is split equally between L1 and L2 or if its all on L1 and N (assuming it can support 5kw on L1 or L2 singularly). The energy on the neutral isn't wasted. It just follows a different path. Do I recommend doing running with extreme unbalanced loads? No. That said, it happens.
Any energy that doesn't do work is dissipated how? Heat. Running loads with a PF less than 1 does cause the generator head to run hotter than if the same power was being generated and the load's PF was 1. PF is an example where the energy you generate and the energy the load uses to to work is not equal and the difference in the two is wasted (as heat). To go back to the example above, If we had 30 amps @ 120v of neutral current being wasted (as heat), the generator head would quickly overheat and fail. Neutral current isn't wasted energy. This could be an error in semantics but I wanted flush it out some to clarify.
Sorry to sideline the original post. I hope this is information that is helpful.
I was asking those questions to make the point that the return path doesn't matter in regards to fuel efficiency or energy waste. The engine won't be loaded any differently whether a 5kw load is split equally between L1 and L2 or if its all on L1 and N (assuming it can support 5kw on L1 or L2 singularly). The energy on the neutral isn't wasted. It just follows a different path. Do I recommend doing running with extreme unbalanced loads? No. That said, it happens.
Any energy that doesn't do work is dissipated how? Heat. Running loads with a PF less than 1 does cause the generator head to run hotter than if the same power was being generated and the load's PF was 1. PF is an example where the energy you generate and the energy the load uses to to work is not equal and the difference in the two is wasted (as heat). To go back to the example above, If we had 30 amps @ 120v of neutral current being wasted (as heat), the generator head would quickly overheat and fail. Neutral current isn't wasted energy. This could be an error in semantics but I wanted flush it out some to clarify.
Sorry to sideline the original post. I hope this is information that is helpful.
Scoobyshep
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You do you.
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Here is how we do it here in Germany. Every house and or building gets 220/380 three phase to the building. When I wire a house/building, I have general info from the owner as to what he has for 380, (better said 400) three phase applyences in his house. So that's a no brainer. Hook em up. Then we would look at what rooms/spaces are left over in the building. The 220 circuits would be as evenly as can be expected, divided between the three phases. Of course there will never be an evenly balanced load between the phases. Some rooms/spaces NEVER get used, or very seldom, and other's are high usage. Most homes where I live are two family, (at least) homes and the imbalance is even higher. And its simply not that big a deal. Yes, load up one or two phases to the max, and one phase not, it can be a worry. But in the norm, its simply not enough to worry about. I can not see this being a problem.
Howdy,
Just stop!
If you do not understand 3 phase, do not go there.
In a large industrial, big machines run on 3 phase. There is other equipment out these which runs on 3 phase. If you do not have any 3 phase pieces of equipment, you do NOT use 3 phase on your generator.
power out of the MEP-002 is
3 phase = 120/208 17 amps
single phase = 120/240 26 amps
straight 120v 52 amps
Normal US house wiring standard is single phase 120/240 60 Hertz
L1 = HOT
L2 = zero not used
L3 = HOT
Neutral
Ground
The generator will not give you more power for plugs at 3 phase. Most US big appliances and equipment operate at 240v 60Hz
110v - 115v - 120v are all the same naming convention.
220v -230v -240v are all the same naming convention.
Some of the US appliances can work in a 3 phase environment. The motor will specifically state that it list 208v
I'm not quite following.
If a generator is 3-phase, operating at a fixed speed (1800 rpm), then power absorbed is a function of torque on the rotor. Torque is a function of the combined load on the 3 phases. For example, shouldn't a 15kW generator not load each phase at 5kW? (average)
Now if the loads were imbalanced, even if a single phase exceeded 5kW, say 7kw, 5kw, and 3kw, wouldn't the average torque load and therefore power absorbed still be 15kW? Now there would be fluctuation in torque as the field rotates, which would cause some inefficiencies.
Flow through the neutral conductor would be equal to the phase imbalance at any instant in time, but I wouldn't say the energy is wasted or causes additional load on the engine, the power just returns on a different path through the stator.
Wouldn't the bigger concern be a voltage imbalance between the phases? There is only one field coil shared between 3-phases, every load imbalance would cause a voltage imbalance.
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I'm not quite following.
If a generator is 3-phase, operating at a fixed speed (1800 rpm), then power absorbed is a function of torque on the rotor. Torque is a function of the combined load on the 3 phases. For example, shouldn't a 15kW generator not load each phase at 5kW? (average)
Now if the loads were imbalanced, even if a single phase exceeded 5kW, say 7kw, 5kw, and 3kw, wouldn't the average torque load and therefore power absorbed still be 15kW? Now there would be fluctuation in torque as the field rotates, which would cause some inefficiencies.
Flow through the neutral conductor would be equal to the phase imbalance at any instant in time, but I wouldn't say the energy is wasted or causes additional load on the engine, the power just returns on a different path through the stator.
Wouldn't the bigger concern be a voltage imbalance between the phases? There is only one field coil shared between 3-phases, every load imbalance would cause a voltage imbalance.
You are correct. Load is load. Even an imbalanced load does work so its not an efficiency problem.
The diagram is a simplified version of an alternator. There will be more pole groups than is represented so the rotation distance between peaks of magnetic flux will be a lot closer together. That will give a smoother torque load on the engine.
Load imbalance can be an issue with the voltage regulator. If the VR samples only one of the phases for regulation, voltages can get a little wonky if you are heavily loading that phase OR heavily loading the other phases.
Scoobyshep
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As a load is applied the engine has to put out more effort to keep the rpm at the desired level. An unbalanced load will impact voltage to a small degree. Any unbalanced load goes back to the head on the neutral. The load carried by the neutral is energy that can be better spent, if it were completely balanced the current is used more efficiently then being wasted in the neutral. In the example I was giving earlier (more of a worse case and yes I have seen people do this with portable sets) 1 leg heavily loaded causing the engine to work harder and consume more fuel while the other leg was not being used as much. The simple point I was makeing is be mindful of what you hook and where. End of the day you do what you want and if you reduce your efficiently by having a high neutral current you have every right to. Have fun with it. Can you practically balance a load perfectly ? Not unless you are in a very well controlled environment. Should you make an effort to get close? Absolutely.I'm not quite following.
If a generator is 3-phase, operating at a fixed speed (1800 rpm), then power absorbed is a function of torque on the rotor. Torque is a function of the combined load on the 3 phases. For example, shouldn't a 15kW generator not load each phase at 5kW? (average)
Now if the loads were imbalanced, even if a single phase exceeded 5kW, say 7kw, 5kw, and 3kw, wouldn't the average torque load and therefore power absorbed still be 15kW? Now there would be fluctuation in torque as the field rotates, which would cause some inefficiencies.
Flow through the neutral conductor would be equal to the phase imbalance at any instant in time, but I wouldn't say the energy is wasted or causes additional load on the engine, the power just returns on a different path through the stator.
Wouldn't the bigger concern be a voltage imbalance between the phases? There is only one field coil shared between 3-phases, every load imbalance would cause a voltage imbalance.
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I'm not quite following.
If a generator is 3-phase, operating at a fixed speed (1800 rpm), then power absorbed is a function of torque on the rotor. Torque is a function of the combined load on the 3 phases. For example, shouldn't a 15kW generator not load each phase at 5kW? (average)
Now if the loads were imbalanced, even if a single phase exceeded 5kW, say 7kw, 5kw, and 3kw, wouldn't the average torque load and therefore power absorbed still be 15kW? Now there would be fluctuation in torque as the field rotates, which would cause some inefficiencies.
Flow through the neutral conductor would be equal to the phase imbalance at any instant in time, but I wouldn't say the energy is wasted or causes additional load on the engine, the power just returns on a different path through the stator.
Wouldn't the bigger concern be a voltage imbalance between the phases? There is only one field coil shared between 3-phases, every load imbalance would cause a voltage imbalance.
how do i make sure the engine is set at 1800 rpm? is the 60 hertz about 1800?
Scoobyshep
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Usually on generator people don't cross with worrying about RPM frequency is the thing you need to watch. frequency and RPM are directly related to each other
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1800 rpm is exactly 60 hs on a 4 pole generator (which this is). On a 2 pole gen head the engine rotates at 3600 rpms. (double the poles in the gen head, half the rpms), as long as it's a generator that is directly mounted to the engine output.
rpms is rotations per minute, hertz is cycles per second. so 60 cycles per second is 3600 cycles per minute. As stated above, different generator designs can change the required rpms for a certain frequency, but unless it is an inverter based generator system or some specialized system that manipulates the field rotation speed independent of mechanical rotation speed (Generac sold one in a standby generator for a couple years, but has discontinued it due to too many reliability issues and cost of parts) for 60hz you'll either have 3600 or 1800 rpms (and on rare occasions 1200, or any other number that multiplies cleanly into 3600)
Whatever you hook up to the generator isn't going to care if the engine is spinning 1800, 3600, or 10k rpms, as long as the frequency is correct for it's purpose, be it 60hz here in the U.S. or 50 hz for many other places in the world.
(and let's not even get into gearbox driven generators or belt driven generators as the entire concept of engine speed requirements go straight out the window)