Electric Motor Secrets

[nali2001]

Back spike capture

Lost of good experiments going on there lately!
But it might be time to move onto the more 'big boys' capture techniques.

You need to pulse both the pos rail and neg rail together.
There is a lot to this but to put it simply you have much limitations in how you are going to collect this energy.

Quick example.
Imagine this energy is a compressed spring, it is supported at one end by a red bracket and supported at the other end by a green bracket. Well if you are going to suddenly release its compression only at the green end, you have still got pressure at the red end as the spring keeps expanding. Ok, now lets suddenly remove both the green and red end together, there is no more pressure in our supporting frame which means the system is completely free and isolated from what the spring is doing. Mechanical and electrical all have the same effects.

(Side note: The purposed technique is not mine but from a well respected engineer I work with)
Steven

[Peter Lindemann]

Core Material

elias,
yes I tried various frequencies with the 555 timer. I think, that the optimum frequency sweetspot is somewhere around where the pulse lenght is eaqual to the current rise time in the coil and that varies with different coils. I should get a function generator for these tests, because it is hard to adjust the frequrncy correctly with the 555 timer.

Peter,
are there any more tests you want me to do before I move on with a different aporach? Because with all the tests I have made, it does not look like that the problem with a low recovery is in the transistors, timing or frequency, it must be in the core material. If there is nothing I can do about this design anymore, then I have some other ideas
Thanks,
Jetijs

Jetijs,

We started this investigation with the assumption that the problem was the core material. I agree with you, that the tests you have run seem to have eliminated the other possible factors. Its your project, so do what you believe is best. I have no other suggestions at this point, other than replace your core and rotor material with something that behaves better magnetically.

Peter

[Peter Lindemann]

How is your motor?

Lost of good experiments going on there lately!
But it might be time to move onto the more 'big boys' capture techniques.

You need to pulse both the pos rail and neg rail together.
There is a lot to this but to put it simply you have much limitations in how you are going to collect this energy.

Quick example.
Imagine this energy is a compressed spring, it is supported at one end by a red bracket and supported at the other end by a green bracket. Well if you are going to suddenly release its compression only at the green end, you have still got pressure at the red end as the spring keeps expanding. Ok, now lets suddenly remove both the green and red end together, there is no more pressure in our supporting frame which means the system is completely free and isolated from what the spring is doing. Mechanical and electrical all have the same effects.

(Side note: The purposed technique is not mine but from a well respected engineer I work with)
Steven

Steven,

Thanks for the two-sided switch idea. John Bedini has used a similar circuit for years, developed by his late friend, Ron Cole.

So, have you finished and tested the motor you built and posted photos of earlier in the forum? We are all very interested to know..........whatever you are willing to share.

Peter

[Jetijs]

Steven, glad to hear form you
If I understood you correctly, then what you are suggesting is that one should use two switches, one on the positive side of the coil and other on the negative side. Then you must switch them on simultaniously and let the coil get the core magnetized, and at the end of this cycle, you need to switch both switches OFF at the same time? In my circuit There is only one (negative) side of the coil switched off and on, the other (positive) side is always connected to battery positive. Did I understood correctly?

Peter, if there is nothing I can do about my current motor, then I would like to go on with a simple induction motor startor core as my startor, just like Steven did, this has may advantages, first of all, the core material best suited for this purpose, there is a bigger area of attraction, the rotor wont move on its inertia at any time, because there will constanly be an attraction force. Also the startor core will be already perfect and I would not need to do any machining work on it. All I need will be only a rotor, and it is much easier to cut the rotor to the diameter needed to fit the startor, than to machine both out of nothing. I think I could make the rotor with a silicon steel lamination core since lighty kindly ofered to send me some silicon steel plates. Also since I need these plates only for my rotor, I wont need very much material for this compared to my current design. The wiring will be a pain in the ass, but all in all this design should be easier for me to make with the tools I have
What do you think about this?
Thanks,
Jetijs

[Peter Lindemann]

Moving On

Steven, glad to hear form you
If I understood you correctly, then what you are suggesting is that one should use two switches, one on the positive side of the coil and other on the negative side. Then you must switch them on simultaniously and let the coil get the core magnetized, and at the end of this cycle, you need to switch both switches OFF at the same time? In my circuit There is only one (negative) side of the coil switched off and on, the other (positive) side is always connected to battery positive. Did I understood correctly?

Peter, if there is nothing I can do about my current motor, then I would like to go on with a simple induction motor startor core as my startor, just like Steven did, this has may advantages, first of all, the core material best suited for this purpose, there is a bigger area of attraction, the rotor wont move on its inertia at any time, because there will constanly be an attraction force. Also the startor core will be already perfect and I would not need to do any machining work on it. All I need will be only a rotor, and it is much easier to cut the rotor to the diameter needed to fit the startor, than to machine both out of nothing. I think I could make the rotor with a silicon steel lamination core since lighty kindly ofered to send me some silicon steel plates. Also since I need these plates only for my rotor, I wont need very much material for this compared to my current design. The wiring will be a pain in the ass, but all in all this design should be easier for me to make with the tools I have
What do you think about this?
Thanks,
Jetijs

Jetijs,

I agree. The design you built I had only proposed as a "stylized design" to show the relationships of the rotor and electromagnet. The design works, as you have seen, but is not the best for high power outputs. It's a great little demonstrator design.

The "notched drum" rotor, like Steven has shown, is going to produce a much more powerful motor. Before you try and build something along these lines, I would like Steven to tell us how his motor works.

Personally, I believe his pole pieces are a little too close together. Unlike a standard "Switched Reluctance Motor", this motor has to breathe. The field must have time to grow to maximum and decay to zero before the next cycle starts. The field must be completely gone for the rotor pole face to slide easily away from the stator pole or the speed of the motor will be restricted. There must also be sufficient space between the poles to prevent a forward attraction force from being partially negated by a reverse attraction force because the features of the physical geometry are too close together. As you can see on my little YouTube films, the test motor has no speed restrictions because there is plenty of time in-between attraction cycles. Your current motor was starting to show many of the right performance characteristics, in spite of the unfavorable magnetic behavior of your rotor and stator.

Since we both want you to build a successful motor, if we are going to abandon your current set-up, let's take all the time necessary to discuss motor operation theory and materials performance so that the next model you build has no hidden problems that show up after all the work is done.

So, Steven,....moment of truth.....what is going on with your motor?

Peter

[nali2001]

Motor

Well there is not much going on with my motor since it is broken. You know the ends parts of each side of the motor are made of an aluminum plate with a Plexiglas plate on top of that, which actually holds the bearing. Well these two plates are glued and also bolted together and after that machined at the same time to get the accuracy needed. But not too long ago I lubricated the bearing and so there was also oil on the Plexiglas plate. Well now stupid as I am I took a cloth with some thinner to clean it off. Well thinner and Plexiglas gives you a real interesting effect. The thinners actually creeps in all these sub-little machined grooves and kind of works its way from there into the Plexiglas cracking it like mad. In just 2 seconds the whole plate was cracked up. There are countless of cracks running the whole length of the Plexiglas. Looks the same as these 'fractures' you see sometimes in crystals. So in other words it is useless now. And on top of that I have no material right now to remake that end piece. So don't expect results any time soon.

Steven

[nali2001]

Some input

One thing I feel that also must be addressed is that, on the one hand it is nice to have coils with a low impedance since it gives good squarewave rise times. But on the other hand one needs to keep in mind that if your core material can not 'keep up' with that sharp rise time there is actually a loss. When you overlay the rise time of the coil and the maximum magnetic rise time of the core material you can see what you are wasting. The coil should not be faster then the core material will allow.

Plus also it might be advantages to reverse the input polarity of each attraction cycle since if you are constantly blasting the core with the same polarity it might be causing some 'permanent' residual same polarity magnetism while running. Especially in non grain oriented steel. (this can't really be tested at stand still) which hinders real magnetic gradient changes. Reversing the polarity actually pulls the magnetism to a zero state before it reverses. So more drastic magnetic changes should occur.

Regards,
Steven

[Jetijs]

That's a shame, Steven.
I also had some breaking experience with plexi glass. It does not love any acids or solvents and breaks at the weakest stressed spots. I found that polycarbonate works a lot better, it is as easy to machine, but it is more dense and wont break if bent or hammered. Maybe you can get your hands on that?
Keep us informed about your success
Thanks,
Jetijs

[Peter Lindemann]

Thanks For The Up-date

Well there is not much going on with my motor since it is broken. You know the ends parts of each side of the motor are made of an aluminum plate with a Plexiglas plate on top of that, which actually holds the bearing. Well these two plates are glued and also bolted together and after that machined at the same time to get the accuracy needed. But not too long ago I lubricated the bearing and so there was also oil on the Plexiglas plate. Well now stupid as I am I took a cloth with some thinner to clean it off. Well thinner and Plexiglas gives you a real interesting effect. The thinners actually creeps in all these sub-little machined grooves and kind of works its way from there into the Plexiglas cracking it like mad. In just 2 seconds the whole plate was cracked up. There are countless of cracks running the whole length of the Plexiglas. Looks the same as these 'fractures' you see sometimes in crystals. So in other words it is useless now. And on top of that I have no material right now to remake that end piece. So don't expect results any time soon.

Steven

Steven,

Thanks for the up-date. I'm sorry to hear of the breakdown of your plastic end plates. So, at this point, your excellent motor design remains untested.

I really appreciate your participation in this forum. Your advanced insights are very useful to other experienced model builders. I know it seems that I tend to suggest things that contradict your posts, but I am trying to illuminate a path for less experienced experimenters. Your suggestions and solutions are viable and I was looking forward to hearing of the test results of your motor. So, again, I'm sorry that will be delayed.

OK, Everybody: This is a good reminder for experimentalists that all kinds of unexpected problems can arise during a project like this. And even seasoned model builders, like Steven, run into these things. So, if things seem to being going slow for you, don't be discouraged!! This is what R&D looks like.

Peter

[Jetijs]

Hi all
Just realized that I forgot to include the switching current in my calculations. If I subtract that form the input current, I get a better IN/OUT ratio. I recalculated my data and found out that instead of 24% I am getting back 30% form my core. It is still too little, but this is just for information.
Anyway, I got my hands on a bigger induction motor core. I took it out form an old Russian 180W AC motor, that I found laying around. The plates are not isolated form each other, you can see four welding stitches on each side of the core. I think, that the hardest part will be the wiring of this core, I will this and see how it goes. If I manage to do this, the rest should be easy





Thanks,
Jetijs

[Peter Lindemann]

An Idea...

Hi all
Just realized that I forgot to include the switching current in my calculations. If I subtract that form the input current, I get a better IN/OUT ratio. I recalculated my data and found out that instead of 24% I am getting back 30% form my core. It is still too little, but this is just for information.
Anyway, I got my hands on a bigger induction motor core. I took it out form an old Russian 180W AC motor, that I found laying around. The plates are not isolated form each other, you can see four welding stitches on each side of the core. I think, that the hardest part will be the wiring of this core, I will this and see how it goes. If I manage to do this, the rest should be easy





Thanks,
Jetijs

Jetijs,

The cores look fine and I doubt if the welding ribs will cause much of a problem. What I suggest is this, wind each leg with at a bi-filar winding (so you have the option of an isolated output) and bring each set of windings out by themselves. This way you can series or parallel various windings to create different configurations without having to rewind the core.

My recommendations would be to make your first rotor have eight (8) pole faces to match with 1/3rd of the stator core pole faces at one time. The motor would be wired so there are three sets of 8 coils to come on sequentially. The cycle begins when the #1 coil set comes on to attract the rotor, turn off, and then SKIP the #2 pole face. Next, the #3 coil set would turn on and attract the rotor, turn off, and then skip the #1 pole face again. Next, the #2 coil set would come on and attract the rotor and turn off. Then skip the #3 coil set to start over at the #1 coils.

This gives the motor the time to breathe I am talking about. These pole faces are quite narrow, so you will need some pretty big gauge wire to get a rapid rise time.

You'll need three optical sensors for the commutator control.

The fact that your stator section has 24 sections makes this design possible. This may have good possibilities.

What do you think?

Peter

[Jetijs]

Peter,
I like your idea of three phases I tried to do some test winding today to see how hard it will be. I had a gauge 21 and gauge 16 wire. First I tried the AWG 16 wire, I must say, that this is very hard, because the wire is thick and hard to straighten out in the long gaps. Then I tried the AWG 21 wire. This was a bit easier, I could get about 15 turns on a single core so that there is enough space for 15 windings on the next core, but there is the same problem Steven had, the sharp edges of the cores scrap the isolation of the windings off and that makes a short to the core. The isolation will be a hard task. Also it is very difficult to make a bifilat coil arount each core. I think that If I used a thinner wire, it would be a lot easier, but in that case I would need to run the motor on higher voltage. How do they wind the motor cores industrially? I doubt that they do that by hand
We have a small motor rewinding company some 40 miles away, I will wisit them and see how they do this. Maybe they can help me with this

Edit: I figured, that if the coil rewinding company wont be able to help me, then maybe I could make my own startor core with a design similar that in the pictures above. That design allows the startor core to be machined in the lathe and to get the maximum precision and minimal air gap. My previous startor could not be machined in a lathe because of its geometry and that was a big problem. Also, If I will make my own startor, then I can make as much cores as I want and also the space between them will be adjustable. The winding of such a custom made core would be alot easier, because there would be more space between cores. I will make a 3D CAD drawing of such startor and post some pictures, then you could tell me what you think

Thanks,
Jetijs

[lighty]

but there is the same problem Steven had, the sharp edges of the cores scrap the isolation of the windings off and that makes a short to the core. The isolation will be a hard task.

Contact the winding shop and convince them to sell you some mylar sheets. They're usually used for isolation and to prevent chaffing in the windings of the motor. There are some similar materials also used by winding guys that you could use and they're all extremely cheap.

[nali2001]

Winding

Yes winding these cores is a real pain. At least the way we/you want to wind it. I have been in some motor winding shops and they indeed do these 3 phase windings by hand and it is easy since they just pre wind much of it on a wooden form or something and than chuck the whole lot into the slots:
http://normandy-repairs.com/images/p...INDING%202.jpg
But that is not possible in our case. But anyway I had to rewind the thing at least like 5 times because somewhere along the way there was a short (use the ohm meter) I finally used cloth soaked with resin/epoxy on the edges. When this hardens it is a very tough and isolated surface. I still can not think of another realistic way of doing it otherwise.

Your core is from what I can see 90% identical to mine. Although I had no weldings seams. But that is no issue.

Regards,
Steven

[Jetijs]

Steven,
thanks for the explanation and the picture. But why is such a winding method not possible in our case? Why can't we just prewind each coil and then just put it in those slots? After all windings are done, we simply need to solder the needed coil ends together in series.