Just mount a drimel tool or Roto zip tool in the Z-axis and use it to cutout the shapes for a laminated generator. Wal-la (not Walmart) assemble the parts into the size needed to make a high speed generator (30,000 rpm). Please note that metal thickness is less than 1/4" so should work...

Bob Teeter

Hi Bob,

... i made this with laser-cutted 0,1mm-steel-foil: [forums.reprap.org]

I previous made some tests with milling the foil, what went fine too, but laser-cutting was much faster and with sharper/filigraner contour-details (and in this episode for free ), so i'll prefer lasercutting ...

Viktor

Viktor - How much power is need to cut 20 - 16 gauge steel thru?

Bob Teeter

Hi Bob,

... for cutting steel you need powerfull lasers - common used are Nd:YAG-lasers with some hundreds until some thousand watts.

The 0,1mm-foil we cutted with a marking-laser with 60Watts max. power with a min. spotsize of 50 microns.

When cutting thicker material you need more power and then you mostly have lasers with poorer optical resonanz and so a bigger spot-size too - for this most metall-cutting lasers are in the kilowatt-range ...

Viktor

I think you will need a drag knife too or a spray tool to cut/deposit some form of insulation/adhesive on the laminations.

Laminations that are electrically connected have limited value they loose a lot of energy through promoting eddy currents.

Make a circuit in the right direction (Flemmings right hand rule) and you have an induction furnace.......

aka47

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Necessity hopefully becomes the absentee parent of successfully invented children.

Just thought

Cutting laminations out of thicker material (taking into account previous comments re induction furnace) is probably going to be more cost effective/easier with a plasma torch.

aka47

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Necessity hopefully becomes the absentee parent of successfully invented children.

Ok I understand what you guys are saying but the alternative seem to be this site. I got this information form Zach as he needs to get parts made for rrrf.

[www.emachineshop.com]

What I was trying to achieve is the creation of a machine that will cut out shapes to make a switched reluctance motor/generator. It uses electronics to make it work but it is one of the simplest lightest easiest constructed motor/generators that I can build that will generate 40 Kilowatts of electricity at 30,000 rpms. And also be small enough that it will fit in a cabinet next to your house. How would you like a energy generation system at your house that can supply all the electrical/heating/cooling needs. The energy source is paid for by the byproducts that the system makes. It also makes more energy than you an use so we sell the excess to the electric company beside suppling the needs of your house.

I am very interested it the reprap system because it should help in the parts fabrication and such of these units.

So please understand that these questions and answers are dead serious.

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Bob Teeter
"What Box?"

Bob

I don't think that I for one doubt anyone else's seriousness or sincerity. I wouldn't be spending my time helping other folk if I did. (Better things to do)

The observations re eddy current and induction furnaces remain. The greater the power you are considering in your experiments the greater the losses and the more likely that things will get hot where you don't want them to in a way you don't want them to by orders of magnitude that you really don't want.

Your project sounds fun. However you cut your laminations you must insulate them from each other just as they are in motors/generators and transformers.

Lamination thickness is a trade off.

Make them too thin and you have more insulation than magnetic material but less heating/electrical loss.

Make them too thick and you have less insulation than magnetic material but far more heating/electrical loss.

Laminations are not a random thickness.

I don't know if you would get sufficient flux density in/through a composite material for your proposed project but this is the direction I will be headed in for my alternator designs.

ie mixing magnetic material with a resin binder and casting it into shape.

Quite what to use as magnetic material and how to process/treat it to acheive something that is good for a magnetic circuit (ie flux capacity and reluctance) but does'nt conduct electricity will be the subject of much experimentation.

I suspect for the figures you have quoted this is unlikely to suffice.

As I understand it most laminations are relatively thin and are stamped out. (Cheap mass production). They are coated with something thin and insulating (ratio of insulation to magnetic material) assembled, dipped in thermoset resin and baked. The resin step stops them rubbing together when in the presence of an alternating magnetic field and wearing out their very thin insulation.

Use a CNC milling head to cut/machine/sharpen yourself a stamp or die and then make a hydraulic press using a hydraulic jack etc and stamp your lamination components. You can then experiment with insulative coating pattern and thickness.

Other than that you will be spending a lot of time waiting to mill out the number you will need.

Getting them made to order is great when you have a final design that works. It could be very expensive whilst you are doing the experimental thing. Particularly if the design wasn't quite right a 40Kw induction furnace will make spectacularly short work of your expensive laminations.

Hope this helps

aka47

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Necessity hopefully becomes the absentee parent of successfully invented children.

Andy - I like your idea of mixing magnetic material and resin and casting the shape need BUT I my generator there are no magnets. All of the magnetic energy need is generated by the initial pulse sent to the coil and the initial magnetic field creates the additional energy used to generate the energy. So I do like your idea of milling the dies for punching out the laminations for the generator/motor. This generator/motor design is very easy to make. It does take a gsp processor to run it. But the nice thing is that the information needed is documented on the internet including the code for running the motor from the ic manufactures. I think that the laminations should be coated with some kind of varnish to isolate it form each other. Thanks for the help.
I you have a minute I have documented my project at:

[www.teeter.com]

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Bob Teeter
"What Box?"

Bob

I think you are (probably quite understandably) confusing what I mean by magnetic material or may be I confused what I meant by magnetic material.

I am referring here to using material that is compatible with a magnetic circuit ie ferrous material. Not actually directly constructing a magnet as such. But be sure that a magnetic circuit will at some time or other become energized with flux. That is it's purpose.

A laminated arrangement is a magnetic circuit as is one made of composite material.

The material itself is not a magnet until you magnetize it (DC coil, permanent magnet etc) but for the duration it is magnetized it may behave as one. Material can be described as hard or soft. Hard material typically retains more magnetization once you stop energizing it (The domains stay aligned) soft material looses it pretty much straight away (but not completely this is described as residual magnetization and links to hysteresis)

Put aside motors and generators for a second and consider a transformer.

You have two coils forming a primary electrical circuit and a secondary circuit. These are interlinked by a magnetic circuit (remember Flemming's right hand rule, generation as opposed to motion etc). AC Electrical Power flowing in the primary induces Alternating Magnetic Power in the magnetic circuit which in turn induces AC Electrical Power in the secondary.

Your magnetic circuit in this case is energized if you like by the power in the primary. You are creating magnetic flux which is constrained/directed by the ferrous materials (Usualy soft) that comprise the magnetic circuit.

Magnetism will pass through a non ferrous medium like vaccuum or air but tends to spread out in all directions. (Remember the thing we did in school with a bar magnet and iron filings). If you have a magnetic circuit that is a 'C' shape then the coupling from one side of the "Air Gap" to the other (think of N & S as being equivalent to + and - in an electric circuit) is directly influenced by the size of the air gap. In a transformer there is practically no Air gap so all of the flux is concentrated into the magnetic circuit and linkes more closely the Primary and Secondary coil.

Your magnetic circuit can be formed by Laminations (Standard transformers are) or Composite Materials ie the ring in a toroidal transformer. the 'E' core in a pot core etc.

In this discussion it is worthy of note that the design of the magnetic circuit is as critical as the design of the electrical circuits if everything is going to play nicely together. Pretty much like any transmission line really. (Mechanical, Hydraulic, Electrical etc)

OK

moving on from the transformer lets pull the transformer apart and make on half of it into a motor and the other half of it into a generator.

AC electrical energy is converted to alternating Magnetic energy which is converted into rotational mechanical energy (Torque) travels down the shaft of the motor and turns the shaft of the generator where rotational mechanical energy is converted into alternating magnetic energy which is converted into AC electrical energy.

So in the theoretical transmission line we just constructed, every linkage along the way has to be able to handle the amount of energy we are attempting to transfer. Any mismatch or loss is likely to result in things getting hot and energy being lost as heat and not transmitted down the line.

The magnetic circuit/s however constructed are just so much more energy transfer and have to be equal to the task.

Hope this explains a little better.

cheers

aka47

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Necessity hopefully becomes the absentee parent of successfully invented children.

Andy - THANK YOU. I can use a magnetic material and cast the rotor and stator of my setup. If I build my molds correctly I can cast my fields into place without a problem and increase the field density about 20%. I also can cast the rotor in 2 phases as the first phase creates the 4 lobe rotor and the second phase without the magnetic material to finish the rotor to a cylindrical shape. What I am building is a 6/4 switched reluctance motor/generator. I will use the motor function to initially wind the turbine and generator/motor up to about 5,000 rpms. With about a 10 second delay I then can apply steam to the turbine and bring the unit up to operational speed of about 30,000 rpm. By the way a unit that is 370 mm long and 152 mm in diameter generates 300 KiloWatts of electricty. So size wise I am not to worried.

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Bob Teeter
"What Box?"

Hi Bob,

... if you want to rotate with 30.000 rpm and have a diameter of the unit of 1,5m then casted objects may be much to 'brittle', so they shurely would rip apart when rotated at this speeds!

With laminating you have to select the right materials too, AFAIK in the beginning of electrification aera most heavy problems in powerplants were malfunctions when vibration breaks the bearings and then the rotors 'disassemble on the fly', explode through the housings and cause very much trouble

Mybe glass-fabrics or kevlar-sheets between the metal-laminates and as hull could do for better stability?

Viktor

Hehehehehe

This sounds like immense fun.

Whilst doing some work for British Rail Research as was, in Derby A guy who used to work for Rolls Royce Research in Derby testing turbine design/construction showed me pictures and bits of turbines that came unstuck at high rotational velocities.

Many of the bits were embedded in the thick concrete wall of the test pit that they used as a safety feature of the test bed.

Loss of balance is apparently a killer and introduces more imbalance as guaranteed destruction ensues.

Some form of restraint in or about the circumference is going to be a must in your design as is achieving and maintaining balance.

Out of curiosity have you considered reducing the RPM from your turbine through a planetary gearbox or some such whilst increasing the number of apparent poles in your alternator design.

You will get the same frequencies but at a greatly reduced RPM at the alternator end.

In testing etc then you need to worry less about the RPM of the alternator. (still some though)

I guess another alternative to consider is a laminated shell filled with composite material.

The designs I have been thinking about for alternators are Axial as opposed to Radial this makes it easier to place a non conductive restraint band around the circumference of the rotor as it doesn't add to the air gap.

Take a look at some of these.

I appreciate this is'nt what you are wanting to do but the constructional detail of some of the components could be useful if extracted. Hugh Piggot does some good books too that explain a lot of complex stuff in understandable terms too. (It certainly contributed to my understanding a lot)

[www.scoraigwind.com]

[www.atm-international.com]

cheers

aka47

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Necessity hopefully becomes the absentee parent of successfully invented children.

Thanks for the input. I have been reading Hugh Piggot for quite a few years and I like his work. About the speed issue. The turbine that we are using is a non-bladed turbine. Also the turbine and generator/motor are on a single shaft. The generator is about 6" in diameter and about 12" long so I am not so worried about the speed issue. My largest concern about using a cast item is dynamic balance so that is why I was going to use laminates with varnish coating. But maybe it would be better to use laminates with cast separators that contain magnetic material. By the way viktor the 300Kw unit is about 6" in diameter and about 15" long. My generator should be about 1/5 that size but it is not a linear scaling.
But again thanks for the input it does help.

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Bob Teeter
"What Box?"

Just as a piece of information about the generator. The paper that has the information on the generatiors has 2 low speed generators of 30,000 rpms. The sizing info is a follows:

Unit #3:
speed: 30,000rpm
Stator Outer Diameter is 152mm
Stator length is 370mm
Rotor Outer Diameter is 76mm.
Rotor length is 370mm

Unit #4:
speed: 30,000rpm
Stator Outer Diameter is 273.6mm
Stator length is 165mm
Rotor Outer Diameter is 136.8mm
Rotor length is 165mm

As you can see these units are not large physically but do generate a lot of power.

Unit #1:
speed: 100,000rpm
Stator Outer Diameter is 152mm
Stator length is 200mm
Rotor Outer Diameter is 76mm
Rotor length is 200mm


All units generate 300Kw of power. The major difference is that the slow speed units can use AISI M-15 metal and the high speed unit uses AISI 4340 metal this is due to the required yield strength of the rotor.

If you want to read the report it is here:
[delphi.com]

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Bob Teeter
"What Box?"

Hi Bob,

... maybe you should first try with a claw-pole alternator - only one coil, two star-shaped metall-sheets with bended tips an a rotor with some neodymium-magnets atached.

It's very simple to build and mostly used as light-generator in bicycles, cars and small wind-mills too ...

Viktor

Um, don't want to rain on any body's parade but try checking out the following:

[en.wikipedia.org]

and

[www.tinaja.com]

Finally, try and be a little more critical in what you think is real. Physics hasn't lied yet about this stuff; conservation of energy is real; and crackpots are.

Don't mean to be so harsh usually but this stuff really sticks in my craw. Hucksters selling crap!

Demented

Demented, just because Wikipedia has the Adams motor as a first reference when you look up switched reluctance generator doesn't mean Bob is trying to make one. Read the report he links to, you'll see it is just a generator. You turn the crank, power comes out. No over unity stuff anywhere in sight.

--Blerik

Blerik,

Please reference the ninth post from the top in this thread posted by Robert Teeter on December 16, 2007 at 1:21 PM wherein he states:

"""All of the magnetic energy need is generated by the initial pulse sent to the coil and the initial magnetic field creates the additional energy used to generate the energy."""

That's not simple generation, it's "perpetual motion" if I've ever heard it.

This doesn't take away from the relevance of the construction process since laminated designs are very useful for other relevant motor applications. I'm concerned with the legitimacy of our forums and how they are perceived. Are we a bunch of crack pots looking for the fountain of youth or inventive DIY hobbiests attempting to make a legitimate technology?

Demented

Also, the wikipedia article is a source most people are familiar with and wasn't necessarily the "first reference" I found. It is simply easy, convenient and fairly believable--though some of my profs don't like it much!

Ok - Demented is right to ask the questions he has. BUT one of my questions is. The turbine and generator are on a common shaft that rides on air bearings. There is no metal to metal contact in normal operation. The turbine has to generate 52+ Brake Horsepower to create 40 Kilo Watts of electricity. Where is the over-unity part of this setup. If all you look at is the electrical part of the operation then it might appear that over-unity might be happening BUT what I want to know is where the 52+ bhp went to then. Any system can appear to be over-unity if only part of the system is examined. Mr Don Lancaster wrote a good book in the past about Active Filters in electronics. He has not had much useful to say since then. He currently believes that the only solution for the US gas problem is more gas. I have listened to him for the last 10 years about hydrogen and he still has not contributed to solving the problem but sticks his head in the sand.

My understanding of the use of these forum is the equivalent of sitting in my living room or yours and having a discussion about many subjects and contributing to the total increase of knowledge of the group about the things we discuss.

Dimented - One of the things that I ask you to do is to do a Google search on "generator switched reluctance" and look at the first 20-30 items. This is the basis of what I am working on. But more importantly the project that I am working on has one overriding requirement. That there is no waste generated or occurring in the transformation of initial form of energy to the resulting supplied products from the system. In converting methane to hydrogen there are 3 products created. 1 - hydrogen, 2 - carbon, 3 - heat. If all items generated are used completely then the efficiency of the system while not 100% will be 95%+ efficient. Please note that part of the hydrogen is used to generate heat for the conversion and not the methane. Why because methane will generate CO2 and Hydrogen generates H2O. Now which is the better result in todays world. The carbon can be used or sold as needed, it is pure. The initial use of the heat is to convert the methane to hydrogen and carbon but instead of throwing it away in the air we take the leftover heat and apply it to a boiler to generate steam which is then used to run a turbine that make electricity. We also recover all the heat for other utilization in my/your house.

So while it is correct to question the information being given in these forums. I only ask that if you believe that information being provided is incorrect then find out why the person believes it to be true. This is the method that can lead to full knowledge. Is this not why you are in school? Just so you have some additional knowledge about my project. The newest basic technology that we are using is 80 years old. The switched reluctance motor/generator was discovered 125 years ago and only has reached commercial success in the last 20 years because of the microprocessor which was invented 50 years ago. So I am sorry that I am using things that are really old but then they do work really well.

Edited 1 time(s). Last edit at 12/19/2007 12:08PM by Robert Teeter.

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Bob Teeter
"What Box?"

Demented,

> "All of the magnetic energy need is generated by
> the initial pulse sent to the coil and the initial
> magnetic field creates the additional energy used
> to generate the energy."

This is a perfectly valid description of how the _electromagnetic_ bit of an SR generator works. An SR generator is a very peculiar thing. The rotor is nothing more than a stack of iron plates. No coils, no magnets, nothing. This has some nice advantages; high rpm possible (perfect for turbines), no back emf, simple. It also has some annoying disadvantages. The biggest is that it isn't self starting, because it isn't magnetic. You have to put energy into the stator coils to get the initial flux going through the rotor. Then by rotating the rotor, you add mechanical energy to the flux and take that out of the coils again as electricity. So like any motor/generator, you have to put mechanical energy into it to get electrical energy out of it. And you need a fast microprocessor to commutate the coils (and part of the commutation cycle is recycling some of the energy to power the coils again).

Because it is so good at high rpm, it is used a lot in combination with jet engines. Another reason for that is that all the stator coils can be on isolated circuits, which really helps with redundancy. Most jet engine SR generators can still run when 5 of the 6 coils are broken!

What Bob is trying to do (for as far as I understand it), is couple the generator to a turbine, and he wants to use RepRap to create both the SR rotor and the turbine blades from metal laminates. Making the turbine blades from laminates is iffy, but if he gets it working it really simplifies everything, since you can then use the turbine blades as flux carriers, and combine the SR rotor and turbine into one thing.

--Blerik

Blerik - My design is to make the turbine and generator separate on a common shaft. The shaft will be supported on an air bearing designed by NASA. (I just love to fly to the moon).
[www.grc.nasa.gov]

This just gets more fun everyday.

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Bob Teeter
"What Box?"

Okay, my mistake then. I assumed--wrongly--that we were talking about the entire system being the generator and it was to be run by pumping an initial pulse of energy into the system.

I opologize in general and most specifically to Robert and withdraw my rudness.

Demented

at least your rudeness was in the spirit of defending the good name of the RepRap project.

cheers! and i'm glad things are okay now =)

This switched reluctance thingy sounds remarkably like a bunch of literature I read some time ago about running induction motors as generators.

They sound to be about the same and have the same non-self-start issues.

the way they got around this was to flash some of the Stator Coils with a car battery just enough to give the rotor a very slight residual magnetic field.

It was enough to bootstrap the rest of the whole induce your own, then self sustaining, fields thing.

Basicaly an induction motor runs at a frequency/rpm less than what you think it should. (Most people imagine that they are fully synchronous) this is as a result of it inducing it's own magnetic fields and currents etc in the rotor. the difference between fully synchronous RPM and what it runs at realy is called slip. So the motor runs at synchronous - slip.

If you take the same motor and drive it at synchronous + slip it starts to generate instead of motor. the more you attempt to drive it beyond Synchronous + slip the more you generate. Up to a point.........

The big problem with them as general purpose generators was essentially the non-self starting thing, if you manage to overload them (However briefly) the magnetic fields collapse, wipe out the residual magnetic field that you had originally put there (it degausses itself) and is then so much spinning scrap.

The fix for this is to run it down to stationary, flash the windings again and then run it up again. Pretty poor then as a standard generator if someone turns on one thing too many or the wrong thing.

Key things not to do with this motor as a generator are to attempt to drive inductive loads as these create the momentary overload (With no recovery) condition that collapses the self generating magnetics.

I came across these, reading some great books by a group that used to be called ITDG (Intermediate Technology Development Group) they were doing high-tech, made kitchen table worthy, for use in developing countrys. (They came up with some pretty cool toys for the home constructor, with nowt)

The particular book was called something along the lines of "Pumps as Generators" or some such. (Yup I had an interest in Micro Hydro and Wind Power for a while)

All in all where I am coming to with this is why not do the same thing but make your turbine/generator out of an induction motor with the end plates removed/re-paterned and stuck in line. (A low tech description of a high tech escapade sorry). It may be possible to reface the rotor to make your turbine (if necessary).

cheers

aka47

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Necessity hopefully becomes the absentee parent of successfully invented children.

An induction motor/generator is another form of what I like to call a software motor/generator. You configure power output and torque in software alone. And both the induction and switched reluctance versions can run at zero torque (the advantage of not being able to self start) so you can ignore them if you don't need them. One advantage of induction is that the controller and the software are easier (you only need to know how fast the shaft is turning, not sampling both voltage and amperage at 100+ Khz). And they are less noisy and easier to design. Disadvantages are; less efficient, problems with rotor heating, low max rpm and the rotor is more difficult to make. It is a nice idea to start with an induction generator to get the simpler controller and software working, then swap the induction rotor for an SR one and get that working.

(Oh, and you don't want to magnetize bits of these generators when you want to run them at very high (eg turbine) rpm! You instantly get all the disadvantages of magnets you got rid of by using these magnet-less designs.)

--Blerik