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?

 

[itsmoked]

In principal this could work fine but there are certain requirements like all three units would have to be STRICTLY synchronized. Most inverters create the output frequency through timers and crystals which gets the job done just fine but when trying to hook multiple ones up even the slightest mistiming will cause a large problem. Most of the larger ones like 2kW and up can be combined to produce say 240V 1ph. To do this the two units are synchronized and 180 degrees apart, three phase units would have to operate 120 degrees apart.

Have you asked the maker?

 

[Ron14]

I was hopeing to hear that each leg of the motor would keep them isolated from each other.
They would share a common line, but each hot wire would go back to the inverter that generated it.
I have not tried to contact the inverter vender as they are only a supplier in the USA i haven't looked but i'm sure it is manufactured in China or Tiwan.
I know about the frequency issue as i tried to wire two small units togeather, the first time it worked and the next time i saw the smoke.

Thanks for your input

Ron

 

[itsmoked]

Hi Ron14;

Can you tell us more about your application? Maybe we can suggest something.

 

[Ron14]

My goal is to design a portable electric powered system for a tool trailer that uses no gasoline to run the generator.

I have a group of 12 deep cycle batteries that will be wired in parallel for a large amp output.

The three inverters will draw from all batteries at the same time, passing 120 volts thru 5000 watt transformers raising voltage to 240 at about 20 amps each, driving the 10 HP 3 phase motor which turns a 10 KW generator head with a 160 pound flywheel, which will be raised to speed by a 3HP dc motor before engageing the ac supply.

The batteries will recharged from the ac generator.

When this system is up to speed it takes little energy to maintain it's motion, a large load applied has very little drawdown effect on the heavy flywheel.

At this point my goal is to design a cycle that drops a depleted battery out of the group and brings it to full charge before putting it back with the group.

The ideal system would be to have the no.1 battery fully charged as the no.12 battery is at it's design low, and all the batteries in between at various states of charge.

The method for monitoring the batteries can be either electrical or mechanical or a combination of the two.

I have used one inverter/transformer to run a single phase 2HP motor which powered a 5HP compressor and a 225 amp electric welder, but not for an extended period of time.

So far this has been a fun project, and I still have the charging program to work out.

This will eventully grow to a power assist unit for my Ford ranger truck.

Hope this is not too much info
Thanks
Ron

 

[itsmoked]

Ron... No one ever gives toooo much info here. Thanks for ALL that info. Rather refreshing from the usual dribbling effect we often see.

Have you considered a VFD? VFD's happily run three phase motors and allow lots of configuration and adjustment. You can run them from single phase power and, derated some, they will create 3 phase power to your motor/s that will run them in a robust manner. You can also provide them with just pure DC. This might allow you to run them with three inverters without the inverters being in phase. Others here with far more VFD knowledge will hop in and advise.

Meanwhile you could run two of your inverter's to provide all the single phase 120 and 240V loads.

Part of the problem with using inverters to run motors directly is that the motors require very large starting currents which can damage your inverters. Whereas the VFDs are built for this service. They aren't as pricey as your inverters either, I bet.

 

[Ron14]

Thanks..itsmoked

The learning never stops, didn't know what a VFD was so i surfed the web and found a post VFD's for dummies. A few other sites talked about using vfd's and even got close to prices but for larger HP units.

If my understanding is close to right, there might be some value to a bank of 20 batteries in series for 240V DC.

One thing to keep in mind is my intended design calls for keeping a 10KW generator/flywheel at rpm at a constant run time equal to the time of doing a job of short duration in most cases.(as in compressing air till the tank is full,short duration welding, or cutting wood with a saw.)The rest of the time it is running at a low amp draw, just enough to stay at rpm while rechargeing one or more but not all of the batteries.

How many times have we seen a construction job in progress with a gas generator that runs all day, and yet only delivers energy to a unit two or three times per hour, if that much.

Having batteries in, singles or multiples of some configuration, would give the ability for always having a fully charged input at most times while one or more are being recharged.

Before anyone mistakes my intentions, the whole system will eventully run down and need an infusion from a source such as gas or the grid.

This brings us back to the point of running a 10HP 3 phase motor from a 12v dc or? battery system. The VFD does sound like a good option.

As i learn more about this item i want to thank anyone in advance that is willing to share their thoughts and experince with me.

Thanks
Ron

 

[LionelHutz]

Your best bet is using a VFD with the proper DC input directly. The 12VDC to 120VDC converters typically aren't that efficient.

I don't see any point in having the system continually re-charging a battery. The energy you're going to put into the battery being charged will be drawn from the other batteries draining them. When you add in the losses incurred in the electronics and motors/generator by doing the charging, you'll just be draining the other batteries quicker than if you let everything idle. Also, if you series connect the batteries then you do not want them at different levels of charge.

A motor freewheeling and connected to a VFD output will draw very little power from the batteries. It will only draw the losses of the idle motor.

 

[jraef]

A power source that recharges itself? LOL, you are essentially trying to invent a perpetual motion machine! Think about the law of thermodynamics; energy out = energy in minus losses. You should know better. Your concept has some merit, except for the part that LionelHutz pointed out; you will have too many losses in the system to overcome. You cannot store energy in a battery that will be sufficient to recharge another battery. The best you can hope for is to equalize the drain. That does appear to have been your intent based on your wanting to remove depleted batteries and recharge them, but the implementation would be disappointing. You must have some sort of energy input into the equation if you plan on using energy out of it.

One minor tweak however may be to ut a PV array on your trailer that is recharging the depleted batteries. The recharge rate would be slow, but at least it is an input instead of a depletion.

As to the VFD part of this, you could use a standard VFD and use a voltage doubler system to step up to the right DC level for input (300VDC). That is how you get VFDs that show 120V 1 phase input and 240V 3 phase output. You just have a lot further to go! But if your intent was for that 3 phase output to run just the generator to recharge the batteries, forget it all together.

"Our virtues and our failings are inseparable, like force and matter. When they separate, man is no more." Nikola Tesla
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[itsmoked]

LionelHutz (snigger)
Don't we need ugh 300V of batteries for the pure DC scheme? That's why I was on about using the inverters with rectifiers to come up with the 300V.

Ron14; As Mr.Hutz mentioned you really do want just one bank of batteries. The more you have the more efficient the system will be.

Here's a little ice water for you (sorry). Any batteries will create lousy efficiency. [flush] Something like 60% efficient, so you are going to be dumping that 40% of energy every time you start charging them. A truly efficient system would be an auto-start for your generator or one of those inverter generators that idle so quietly they can barely be heard 10 feet away then leap to whatever speed required to supply the required power.

Alternatively build a trailer scheme that has 300V worth of solar panels (roof) that keeps the 300 Volts of batteries (floor) charged for those moments of work. I would think this would come out just about right. If the solar started to fall behind then a small, regular, generator could auto start and run till the batteries are charged or use shore power.

 

[jraef]

LOL itsmoked, we must have been typing in tandem!

 

[itsmoked]

Yeah!!

Great minds think alike... when they work at all.

I'm glad you touched on the perpetual motion angle. It isn't entirely clear what the OP is up to. I was assuming he isn't up to alchemy. But you never know.

 

[Barry1961]

DC to AC inverters are very cheap and plentiful. While they are not very efficient, 85% at full load and 87% at .33 load, they are more efficient than running a generator full time.

Remember that a flywheel is a mechanical device for storing energy. You put energy into it and you take energy back out of it. To put energy into it you accelerate it, to take energy out you decelerate it. Maintaining the velocity of the flywheel also takes energy, which is your “loss”.

The key point is that the only way to get energy out of the flywheel is to slow it down. The flywheel will not make your system more efficient unless there is a shock load that is more than the drive can handle.

If an air compressor starts and takes 3 minutes the refill the air tank the flywheel would have to be decelerating for the full 3 minutes to keep putting energy back in. What will happen is that when the compressor first starts, 5 times full load current, the flywheel will help the motor/generator for about one second. After that 1 second is over it will become an additional load on the motor generator.

If the motor/generator can handle the load the rpm will not change much from no load to full load, maybe 1780 rpm to 1750rpm. Adding a flywheel will reduce the drop but will slow down the recovery. And it will take just as much energy to speed the flywheel back up as it took to slow it down.

They flywheel will not help the efficiency of the system you have described at all, period, not, nada, no how and no way.

Barry1961

 

[Ron14]

Well guys..

I want to thank all who have shared thoughts with me, as jraef or p3 pointed to policies at the end of his post, i had not read them prior to his comments.

I do seem to fall into #8 catagorie, as i am not formaly educated in eng. I have taken a few hours at a community college in electrical path.

My background for 45 years is too varied to call any one thing a speciality. I have been self employed for the most part in construction and heavy equipment, there have been other fields of exposure such as, marine,aviation, and high tech semiconductor wafer fabrication(AMD).

I have always been a owner operator, so have never commanded a workforce, which means maintanence/repairs have always been at my own hands. This has resulted in basic understanding of several disiplines without a solid foundation in any one of them.

Of all our heros Tesla is my #1.

In my little understanding of heat pump principles and Tesla's Turbine with a certain modification in its construction, there should be three benifits from the transfer of thermal energy from the atmosphere, they are cold air, condensation, electricity or mechanical work.

With all these things said it should be clear how i plan to keep my batteries charged, and why if not now, later i will be red flagged on this forum.

Should anyone care to continue dialog with me please respond with how and best method. Again thanks for your responses as they have been very helpful.

Ron Light

 

[itsmoked]

Atually it is not at all clear on how you are going to keep your batteries charged... How about a clear statement of how everything is going to hook up. Include any new found info.

 

[Barry1961]

You would probably get a more positive response in a different forum.

Overunity has several forums.

http://www.overunity.com/

Fuelesspower has plans that are guaranteed to work. All the way up to 350hp.

http://www.fuellesspower.com/

Good luck, and don’t let math or physics get in your way.

Barry1961

 

[Ron14]

You have all been kind enough to respond, so i'll continue as best i can.

First i do not believe in overunity, but i do believe thermal energy can be extracted from objects or mediums and converted to electrical or mechanical work.

As an example 1 gallon of water has a certain weight, a well known fact. This same gallon of water has a btu value of a certain quanity from 32 degrees to 211 degrees, in which the weight has very little change.

If the water is allowed to drop a given distance for a certain quanity of time there will be a mathmatical value that can be assigned to this action, and if the system can extract and apply the thermal value from 211 down to 32 degrees and add to the value of the weight(kenetic) energy at the same time this would in my mind represent nearly 100% of the total energy available. There will be the normal losses of thermal and friction to known and unknown areas.

If my thinking does not fly in the face of physics then i will try and explain how to accomplish what is in my mind.

One other thing before we get into a very deep subject, is an idea that has been in my mind for some time. An electric motor that is suspended so that both housing and armature can rotate but in opposite directions, each having a flywheel that is of proper size and weight to give equal values of resistance to each unit, if frequency is not an issue then more voltage can be applied and devided between the two counter rotating units thus increasing power by a large factor, if the unit is used as both motor and generator then keeping it cool is a source for heat that is reapplied in the system of thermal conversion. (heat pump cycle)

Hope this has not put everyone to sleep and yet there is so much more.

Ron L

 

[itsmoked]

Do not forget that you cannot work the entropy backwards. Highly organized electricity cannot be made in a one to one manner from disorganized heat. This is reflected in the heavy efficiency losses in the conversion processes.

But alas, I for one do not want to get into a wild discussion about energy recovery and hypothetical energy-savings through novel schemes.

I once watched in horror as two guys went thru thousands of dollars building and running a perpetual motion machine that had a motor running a hydraulic pump that ran a generator that ran the motor.. Sheesh. Sad to the point of disturbing.

 

[Barry1961]

Many people have tried to multiple power or create perpetual motion machines by using flywheels. Many people have spent a great amount of money trying to do it. Some people have made good money selling people kits for free energy machines that the government does not want you to know about.

I don’t know what it is about flywheels that makes people think they can get more out of them than they put in. I think for every person who believes they can multiple power by pumping water back uphill in a hydroelectric plant there are 10 who believe that attaching a flywheel to a motor or generator will multiple the power.

Ron, I really hope you do not spend a bunch of money on this. There are hundreds of millions of flywheels on machines all over the world. The math for calculating stored energy in spinning flywheel is easy and readily found.

I hope you have fun with your project.

Barry1961

 

[Ron14]

Thanks for the kindness in nearly all the post, I seem to have let things get out of context, due to my inability to transfer into words my thinking, understanding, and what i am trying to accomplish.

My original post should have been within the intent of forum guidelines, novel schemes is where we went, for that please accept my apoligies.

Some may have jumped to conclusions about what was being described and how things were going to be used and what results were being expected.

Itsmoked requested a clear statement, as i started to try and do this it dawned on me that it would only continue the novel schemes thinking. Please indulge this attempt at a clear statement.

Barry1961 mentioned multiplying energy with a flywheel, I agree this cannot be done. 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.

My intent is to keep all my energy requirements (in and out ) within the top 5% of this flywheel action. As for adding any additional power to my flywheel my aproach will be to utilize the concept of two sealed chambers one inside the other. The only connection to the outside enviornment would be electrical wires sealed at their thru holes.

The outer chamber is a low pressure zone and the inner chamber is a higher pressure zone. The inner chamber houses completly the motor,generator and flywheel system. The flywheel assembly is made on the basic concept of the Tesla Turbine. It is composed of a group of inner disk and bounded on both sides by heavy steel plates with center openings for air flow.

On the outside of the inner chamber and on either side of the turbine are vacuum motor units, pulling a vacumm on the flywheel unit, also on the outside of the inner chamber are 4 (two on each side) vacuum motors applying a positive pressure to the inside of the inner chamber, and at the same time reducing the pressure of the outer chamber. These six motors will be powered by the internal generator. This air flow is of low pressure and large volume. Still it will have a greater velocity then the speed of the flywheel unit.

The rotation of the flywheel unit by the electric motor keeps the rpm's constant, while the air flow is trying to push thru the disk's outer surface and thru to the internal vacuum in the central area, at a faster rate thus suppling additional energy to the motor (which would show as reduced amp flow).

If my understanding of the first law is correct, then all energy can be accounted for in the two chambers, and the electrical leads from the batteries going in.

Now where i place all my hopes is in the belief that with proper insulation around the inner chamber, and the outer chamber being alum. or copper walls to allow for heat in, this becomes a heat pump, with heat being assorbed equal to electrical energy sent out.

all this being said, i do want to add that the comment about highly organized electricity, and disorganized heat did not go unnoticed. If my thinking is flawed i'm sure this will be the eye opener once i figure it out.

The Three things that have led my thoughts are,
#1 steam jet ejectors
#2 vortex tube coolers
#3 Tesla Turbine therory/with flow thru generator
It is my belief, these three things assembled in in proper configuration will be able to give a heat pump system that absorbs heat and gives off electricity in exact and equal quanities.

If open to the atmosphere the three results would be,
#1 cold air
#2 condensation
#3 electricity
Now that i have totaly ruined my image, i'll refer back to my original post about 3 inverters powering a 3 phase motor and say that most likely VFD's will be the best choice. Thanks for the info.

And "barry1961" thanks for your last thoughts, i have kept my cost down by trying not to buy anything that does not have some other use in my business or hobbies, my costs are only a few hunderd at this point. We have a community dumpster nearby and you would not belive some of the good working things that people throw away.

If time is kind to me there should be some test runs in a few months, and if there are any positive things to report i will make a post, if that is ok.

Thanks
Ron Light