Can 3 inverters be used for 3 phase power ? 3

[Ron14]

I have three inverters and a 10 hp motor and need to know if the three units can be used to supply each leg to the motor, the inverters are modified sine wave units 5000 watt that use 12 volt in and output is 120 volt ac @ 40 amps.
There will be a step up transformer that delivers 240 at 20 amps for each leg.
My question is has anyone tried this and how well did it work?

 

[Barry1961]

"As one article in my past studies stated, " pound for pound a flywheel will store 10 times more energy than a lead acid battery" if this is anywhere near accurate it only represents a storage medium."

1. Weigh the battery in your car, 30lb?
2. Disconnect the coil wire to prevent car from starting.
3. Try to start the car
4. Time how long the engine keeps turning, 1 minute?
5. Make a 30lb flywheel.
6. Make a belt tension “clutch” to crank.
7. Try to start car.
8. Time how long the engine keeps turning, 10 minute?
9. Post your results.

I really don’t think you can make a 30lb flywheel that will crank an engine 10 times longer than a battery of the same weight. It is theoretically possible though, but the flywheel would have to be made of unobtainum to prevent it from self destructing.

Before you make a flywheel you should know they will burst if designed wrong or run too fast. And there is no early warning before they do burst.

Save your money. Learn the math. Do the math. Math is your friend.

Barry1961

 

[GregLocock]

Energy storage per unit weight for a carbon fibre flywheel running in a vacuum via a 98% efficient motor/generator, would be about the same as a lead acid battery, to within a factor of two either way.

The flywheel system could be designed to last for years with no maintenance, which makes it attractive for some applications.

Cost wise there is no comparison, of course. I'd guess the flywheel would be a minimum of twenty times more expensive than a lead acid.

Incidentally, the round-trip efficiency of a lead acid is pretty much defined by the difference in charge and discharge voltage - about 95% efficiency in practice.








Cheers

Greg Locock

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[itsmoked]

GregLocock I think yur dreaming if you think you can get 98% out of a lead acid system.

 

[GregLocock]

Learn to read posts before criticising them.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[itsmoked]

I'm sorry..

Let me restate myself.

I think yur dreaming if you think you can get 95% out of a lead acid system.

Lead acid batteries have an efficiency no better than 80% and this is the pure power in verse power out. If you include the efficiency of the charger/battery "system" as I referred to above, then you are now talking 60% to 70%.

So I don't know what "practice" you are referring to.

 

[GregLocock]

Ooops, oddly enough I've measured it. However I misremembered the number, it is 90%, as the coulombic efficiency is almost 100% but the charge voltage is 2.2V per cell,and discharge is at 2.0. So, sorry, you are right, I was wrong to say 95%, 90% is nearer the mark.







Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Barry1961]

After thinking about it, a car engine already has two flywheels that probably weigh more than the battery. So if you run the engine at close to the speed the starter motor turns it, very low idle, and then cut off the ignition it should continue to spin for about 10-15 minutes. This test will be cheaper and safer than the one I posted before.

You can also put energy into air and take energy out of air. I don’t know off hand what the efficiency of the various methods are but I don’t think they are very efficient. I am not aware of any devices that use air to store energy.

Barry1961

 

[Ron14]

A lot of good questions and comments.

While going thru the site and finding answers as to how to best use the powerful tools at pretty much anyones disposal, i am almost overwhelmed at all the topics and information that is contained in these pages.

I will be considering a lot of things for a number of days i'm sure.

As for your illustration of battery cranking engine, and flywheel turning engine, i think you failed to consider the pinon and flywheel gearing.

However it did bring one thing out and that is, if you use the battery to drive a motor which has a flywheel on its shaft for a given time to a certain speed, then reverse the process so that the motor is now a generator, how much charge is put toward the battery?

Now you have to consider effeciency losses of all three, motor,generator, and battery and possible others.

This is not a 5 min. exercise.

I still have lots of thinking to do.

Thanks

Ron L

 

[jraef]

To me, this original discussion still seems to skirt the edges the first law of thermodynamics, and to my knowledge, that law still stands firm. You cannot get more, or even equal energy out of any system than what you put into it, no matter how many devices you add to the system to try and recover waste.

Vortex tubes for instance look like really interesting devices that appear to separate thermal energy from moving air, but the fact that is constantly left out of discussions about them is how much energy went into getting the air moving in the first place, and it is tremendous! I once worked on a system to keep a man cool in a foundry area using compressed air into a vortex cooler since the compressed air was already available and electricity was not. Base on the worker producing 2400BTU/hr (heavy work), which equates to about 700 watts, the vortex cooler needed 100cfm at 40 psi. What I discovered is that it took 7-1/2HP of air compressor to get that! So that is 5600W input to extract 700W, a loss ratio of 8:1! Can you design a vortex tube to extract energy from low velocity air movement? I suppose, but it would need to be HUGE!

Ron14, here is what I think you are trying to describe:
You want to put energy into a system in a closed environment to start a generator in one chamber, use the generator to run compressor motors that create a pressure differential between the two chambers, and use air flow between them to keep the generator running after the external power input is removed. In addition, you think you can trap the losses in the generator and compressor motors as heat in that chamber, use the heat to expand air in that chamber, adding to the airflow across the generator. I'm not sure where the vortex tube came into your scheme, but it doesn’t really matter to what I think the issue is. IF you had absolutely perfect, and I do mean PERFECT sealing and thermal insulation, at the very best, the system could theoretically sustain itself. The big BUT in this is that absolute insulation and absolute sealing does not, and arguably cannot exist. So in that scenario any even miniscule amount of energy loss would be essentially sap it of it's own sustenance energy, which would (IMHO) have a logarithmic effect on energy reduction, thus dooming it to rapid failure.

And the bigger question is, WHY? It really is not going to create energy, and you cannot extract any useful energy from it without causing it to rapidly decline, so I doubt that it's storage capability will be any better than any existing system, maybe even worse. On top of it all, it will cost an awful lot to make.


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[itsmoked]

Well put jraef. A star.

It is kind of like making a solar panel. Takes a huge amount of thermal energy. Thousand degrees. The metal frame had to be made. It came from explosives, diesel, rubber consumption brought from other countries, etc, etc.

Then it needs to run with full output for 20,000hrs just to break even on the energy that went into making it! Same as a car. People run out and buy a new "more efficient" car discarding a working car whose "inherent" energy is more than all the fuel that will ever be saved with the new one!

The big picture for your project, [besides the, fact that it cannot work], is the same as my above statements. The cost and energy that you might ever derive is offset by the cost and energy and complexity of the device's construction.

 

[Ron14]

well...

This thread has gone longer than i expected from a simple question, but i feel i'm near to an understanding that has been a long time comming.

It's like i'm continually walking into a wall when i know the door is only 2 feet to the left.

It will take a few days to put my words in order (hopefully). For now i'll state what i believe my biggest hangup is, which i felt "itsmoked" was close to seeing when he mentioned working entropy backwards.

I can't seem to understand the difference in a heat pump COP and 100% effeciency.

I have a McGraw-Hill encylopedia of energy, that gives the illustration of a heat pump with a COP of 17.7, and uses the terms " 1(Kwhr) of electric energy to compressor" delivering 3413x17.7=60,000 BTU/hr of refigeration or heating effect as required.

Now to me the value of 1 BTU from electric coil into steam and 1 BTU being absorbed from atmosphere or water into a reduced steam temp of say 40 Degrees is not a bit different.

Now describing the system that produces these effects is what will take some time. But if i can see the light i might not have to describe what i have in my head.

Does this make sense?

Ron L

 

[stevenal]

Except for the resistive losses, heat pumps do not convert electrical energy into heat. They simply move heat around. The COF deals with electrical energy in and heat out ignoring the heat input to the system. By this measure, a gasolene pump is outrageously efficient. A few watt hours of electric power in and lots more BTUs worth of gasolene comes out. And they want $3 per gallon?

 

[stevenal]

Forgot to spell check. Make that "gasoline."

 

[Barry1961]

The starter is only engaged with the ring gear during the act of starting. The starter is only connected to the battery during starting. The starter stator is open unless starting.

You can gear the flywheel any way you want and it will not spin the engine for any length of time approaching what the battery will do thru the starter. For the flywheel to store energy approaching the battery it would have to have an OD so large that the spokes and hub would be paper thin, or less, and be spinning at a very high speed. This of course would cause the flywheel to burst.

Every time you change the state of energy you use some energy to make the change.

Barry1961

 

[Ron14]

Thanks stevenal

I do not understand your gas pump example, but i do understand that the energy to the refigerant compressor is used to move a volume of gas that when allowed to expand has the ability to absord 60,000 BTU, but rather than let this heat just warm a room, why not apply -the 300+? (just a guess) degree gas inside a coil, to a cool water supply that is about to be injected into a steam generator.

I thank i just confused myself again.

Anyway what i thank is close at hand for my understanding is, if each cycle represents 60,000 BTU - 3413BTU how much of the 56,587 BTU could be used to add back into heat that does not need to be generated by a power process?

Now what "itsmoked" stated was, (if i understand right) that the 3413 BTU is (highly organized electricity)
And that the 56,587 BTU is (disorganized heat). When this becomes clear in my mind, the dissapointment will come rushing in, untill then i see this as a large quanity of heat to be used in some way, prior to my electrical generation of steam.

I sure hope this discussion is helping someone else in the world to better understand what i seem to be having so much trouble seeing, and that it is not too much a waste of forum time.

Again THANKS for everyone's generous offer of time and thoughts.

Ron L

 

[stevenal]

I thought my analogy was clear enough. In my gas pump example I ignored the other energy input into the system, the gasoline in the below ground tank. Like the heat pump, the gasoline pump simply moved the energy from one location (below ground tank) to another (vehicle fuel tank). The ratio of fuel energy out to electric energy in is nearly meaningless, and certainly does not qualify as efficiency. Efficiency is the ratio of the total output energy to total input. Neither pump will work the entropy backwards.

 

[itsmoked]

Ron14; Do not confuse "heat availability" with useful energy. Moving a bunch of heat from one side of a wall to another with a COP is a case where a bunch (a whole bunch) of electricity [high entropy] {high quality} is used to shuffle even more [low entropy]{low quality} energy from one side of a wall over to the other side of a wall. The only real gain in the energy being shifted is the {real] gain supplied by the higher quality waste heat being rejected by the compressor. (From the electricy being supplied to the compressor).

 

[Ron14]

Alright guys....

I think i just moved two feet to the left, now if i can just move forward a few steps i'll be thru the door.

I have a job to do ( actually make some money) i'll be back in a few days to try and catch up.

The last two post have helped and i thank i see some light.

Thanks again

Ron L

 

[aolalde]

Returning to the original post and based on all these long extraterrestrial discussion, I do not see how TOM14 could understand and synchronize a three phase system out of three independent drivers.

 

[jraef]

LOL aolalde, we got so far off onto the energy/entropy issue that we lost trrack of the original question! Good point.

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