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  #451  
Old 12-06-2007, 02:11 AM
Peter Lindemann Peter Lindemann is offline
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Hoping for Better....

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Originally Posted by Jetijs View Post
Thanks, elias
I don't quite understand your circuit, maybe if you explained what the circuit does and how should I add it in my circuit, I would try that out. Also that with the closed core, maybe that is why I actually get better results with a open welding rod core than with a closed induction motor startor core. Lets see what Peter has to say. If there is a big difference in the closed and open cores, then I could cut the induction motor startor core in half and test only one half of this core. Because I was hoping for better results with this silicon steel core
Jetijs,

Yes, I agree with you. The silicon-steel should have been able to do better. This result tells us two things. First, that your magnetic core material is returning energy at less that 50% of the silicon-steel. And second, that there may be a problem with the switching speed of your 2N3055's. I always use the MJL21194 by ON-Semiconductor. But I don't know why your 2N3055's aren't working better. Is it possible for you to try this test with a different transistor?

This was a great test to run. We were expecting a result that suggested that your core material was slow, but that the transistors were fast enough. Perhaps they are not doing as well as we thought either.

High speed BPT's are still the device of choice. MOSFET's are difficult to turn OFF quickly, so let's stay with BPT's for now. (Sorry, Elias).

We need to solve (or explore) one issue at a time, so maybe trying a different transistor on your energy return test set-up is a good place to start.

What do you think?

Peter
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  #452  
Old 12-06-2007, 02:41 AM
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Peter,
I just browsed on the local electronic web shop and they seem to have the MJL21194 transistors. They are three times more expensive than the 2n3055, but I will buy one or two to make the tests, also I will have a use for them later. But I doubt that the transistors are the problem, I can't see any fall time on my scope, only rise times and off periods, this tells me that the transistor switches off fast enough, right? Also I used these transistors on some SSG setups and could get some very good results.
I just found some silicon steel open core material form an old contactor relay, I will also do some tests on that material, since this core is open and not closed like the induction motor startor core, maybe this will give some different results. After these tests I will post my results and then we will decide what to do next. I am not gonna quit on this!
Thanks,
Jetijs
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  #453  
Old 12-06-2007, 04:13 AM
Peter Lindemann Peter Lindemann is offline
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I Agree

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Originally Posted by Jetijs View Post
Peter,
I just browsed on the local electronic web shop and they seem to have the MJL21194 transistors. They are three times more expensive than the 2n3055, but I will buy one or two to make the tests, also I will have a use for them later. But I doubt that the transistors are the problem, I can't see any fall time on my scope, only rise times and off periods, this tells me that the transistor switches off fast enough, right? Also I used these transistors on some SSG setups and could get some very good results.
I just found some silicon steel open core material form an old contactor relay, I will also do some tests on that material, since this core is open and not closed like the induction motor startor core, maybe this will give some different results. After these tests I will post my results and then we will decide what to do next. I am not gonna quit on this!
Thanks,
Jetijs
Jetijs,

I agree that the scope shots look like the 2N3055 is turning off fast enough. But in a situation like this, everything must be looked at carefully, and all assumptions questioned. The MJL21194 has a history of working well in circuits like this, so let's see how they behave in your test.

Glad to hear you plan to stick with it.

Peter
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  #454  
Old 12-06-2007, 08:47 AM
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Quote:
Originally Posted by Peter Lindemann View Post
Jetijs,

Yes, I agree with you. The silicon-steel should have been able to do better. This result tells us two things. First, that your magnetic core material is returning energy at less that 50% of the silicon-steel. And second, that there may be a problem with the switching speed of your 2N3055's. I always use the MJL21194 by ON-Semiconductor. But I don't know why your 2N3055's aren't working better. Is it possible for you to try this test with a different transistor?

This was a great test to run. We were expecting a result that suggested that your core material was slow, but that the transistors were fast enough. Perhaps they are not doing as well as we thought either.

High speed BPT's are still the device of choice. MOSFET's are difficult to turn OFF quickly, so let's stay with BPT's for now. (Sorry, Elias).

We need to solve (or explore) one issue at a time, so maybe trying a different transistor on your energy return test set-up is a good place to start.

What do you think?

Peter
Yes thanks for pointing that out. I was thinking of logic circuits instead of power circuits. Finding a way to discharge the base of the bipolar transistor faster would turn it off more quickly and increase the output even more.
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  #455  
Old 12-06-2007, 06:12 PM
hartiberlin hartiberlin is offline
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Originally Posted by elias View Post
Well,

In that circuit I usually charge C1 with a battery and pulse it through the coil into C2, while capturing the spikes in C3, this basic circuit defies the law of charge conservation and you end up with more charge than you started with. It will show how much charge you can capture by using a coil and pulsing the pushbutton (or you can use a transistor) when starting with a predefined amount of charge.

Elias
Hi Elias,
does this mean that this circuit:



is producing more energy than was stored as 0.5 x C x V^2 in the beginning in C1 ?
If yes, you would have already creazed a circuit with COP >1 !

Please let us know more about this experiment.
Many thanks.
Regards, Stefan.
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  #456  
Old 12-06-2007, 06:20 PM
hartiberlin hartiberlin is offline
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Originally Posted by Jetijs View Post

Notice how they get shorter in height when there are more spikes per 25 degree window. That means that I can get the pulses even shorter than the rise time, but nevertheless I can not get more than 24% back. Also the higher the frequency of the spikes, the higher pitch noise the motor gives out.
Any suggestions which way to dig next?
Hi Jetijs,
is your stator iron core solid iron or
laminated iron ?
Maybe eddy currents play a major role here,
that you can only get 24% back out ?
Also , did you see, how much you already are in saturation
in your BH curve of the iron core ?

Peter, is it better to drive the iron into saturation
or not ?
Also it probably depends a lot what kind of
core material you are using.
A low hysteresis metgals alloy would probably be much
better than just iron...
Maybe you also have too much hysteresis losses at the moment.

Regards, Stefan.
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  #457  
Old 12-06-2007, 06:42 PM
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elias elias is offline
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Quote:
Originally Posted by hartiberlin View Post
Hi Elias,
does this mean that this circuit:



is producing more energy than was stored as 0.5 x C x V^2 in the beginning in C1 ?
If yes, you would have already creazed a circuit with COP >1 !

Please let us know more about this experiment.
Many thanks.
Regards, Stefan.
Stefan,


Welcome to this forum. This is unrelated to the topic of this thread so lets move the discussion to the corresponding thread:
http://www.energeticforum.com/renewa...html#post13434
This circuit is an abstract form which yields to more charge, not more energy. But in my opinion it has the potential to produce more energy if we use better coils + better core materials + battery instead of a capacitor + correct timing of the pulses.

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  #458  
Old 12-06-2007, 06:52 PM
hartiberlin hartiberlin is offline
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Quote:
Originally Posted by elias View Post
Stefan,


Welcome to this forum. This is unrelated to the topic of this thread so lets move the discussion to the corresponding thread:
http://www.energeticforum.com/renewa...html#post13434
This circuit is an abstract form which yields to more charge, not more energy. But in my opinion it has the potential to produce more energy if we use better coils + better core materials + battery instead of a capacitor + correct timing of the pulses.



You are right.
I answered you over here and asked the energy question:

http://www.energeticforum.com/13497-post12.html

Please answer this.

Many thanks.
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  #459  
Old 12-07-2007, 04:44 AM
Peter Lindemann Peter Lindemann is offline
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Welcome, Stefan

Quote:
Originally Posted by hartiberlin View Post
Hi Jetijs,
is your stator iron core solid iron or
laminated iron ?
Maybe eddy currents play a major role here,
that you can only get 24% back out ?
Also , did you see, how much you already are in saturation
in your BH curve of the iron core ?

Peter, is it better to drive the iron into saturation
or not ?
Also it probably depends a lot what kind of
core material you are using.
A low hysteresis metgals alloy would probably be much
better than just iron...
Maybe you also have too much hysteresis losses at the moment.

Regards, Stefan.
Stefan,

Since we are trying to recover the maximum energy from the collapse of the magnetic field, keeping the iron below saturation is best.

Also, you are probably right that low hysteresis materials like MetGlas would work the best in a motor like this. But right now, we are just exploring the limits of using low cost materials like cast iron or silicon steel laminations.

Thanks for bringing these ideas up, since they had not been discussed very much yet.

Peter
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  #460  
Old 12-07-2007, 03:12 PM
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My test about the amount of recovery possible

Hi Jetijs,

I did an experiment to see how much output I could get out of pulsing a coil. The picture of the coil used is attached. It is pretty small (about 1cm in length). Probably it is about 5-10mH or less. Its core is about 1mm in diameter and is apparently made of ferrite.

For this purpose I used a 10,000uF capacitor for the input and a 10,000uF capacitor for the output, across the diode. I charged C1 to 12 volts and by pulsing it with an approximately 20% duty cycle at 5KHz I got the output capacitor charged to about 9.15 volts, while some charge was remained on the input capacitor at the end (about 0.5 volts). So I concluded that the efficiency of my pulsing system is about (9.15/12)^2 = 58%. Note that as the charge on the capacitor decreases the spike gets lower in amplitude and reduces the charging effect. I used a 900v FS7SM MOSFET and a square-wave signal generator for this purpose.

Hope this helps ...

Elias
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  #461  
Old 12-07-2007, 05:42 PM
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elias elias is offline
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Another experiment

Hi

I played with the function generator a bit and found something interesting while connecting a lamp to the output along with a capacitor. See the attached circuit. There is a sweet spot for the minimum current drawn from the battery depending on the coil used. it is somewhat a bell-shaped curve. I experimented with the same coil and the result was interesting as it provided minimum current (29mA) to the inductor at about 28KHz and it increased when either increasing the frequency or decreasing it. In my setup I had:
Vin = 12V, Iin = 29mA
Vout = 10.20V, Iout = 27.5mA

The data above yields a recovery of about 80% of the input and it seems promising.
But when using capacitors only as the previous experiment I did at 5KHz, but now at 28KHz 50% duty cycle, I did not get more than 6 volts on the output capacitor. It seems also that lower frequencies with less duty cycle are better than higher frequencies with more duty cycle.

When the input voltage was 18 volts the minimum current drawn from the battery was at 31.5KHz:
Vin = 18.2V, Iin= 38mA
Vout = 16.36V, Iout = 35mA
In this case the recovered energy was about 81% of the input.

I experimented with a larger coil and that one gave me 76% efficiency at its sweet spot which was 2KHz.
In all of these experiments I used a duty cycle of 50%.

In conclusion I have to say that the motor seems to be able to recover the most in a certain RPM, or certain amount of pulses per second. Maybe we can design a system which can stabilize the frequency of the pulses independently from the RPM of the motor. increasing the input voltage, increases the recovered energy a bit.

Regards
Elias
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  #462  
Old 12-07-2007, 09:03 PM
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Quote:
Originally Posted by elias View Post
Maybe we can design a system which can stabilize the frequency of the pulses independently from the RPM of the motor. increasing the input voltage, increases the recovered energy a bit.

Regards
Elias
Are you talking about the motor I am working on? If so, then you have missed, that we already have an independent frequency of the pulses regardless of the RPM's of the motor. The switching is done by a 555 timer.

Ok, I have done some tests today. I used my motor circuit to pulse the coil with a welding rod core. I made these tests with 5 different frequencies. I used two 12v batteries in series (24V) on the input. In the first test I used a 24V battery in the output and pulsed the circuit with one 2n3055 transistor to get the basic results so that I can compare the with other tests. The switching circuit with the 555 timer and the optotrigger consumed 0.09A, that must be taken into account. For the second test I used the MJL21194 transistor soldered on the same base plate parallel to the 2n3055 transistors. This time the switching current was 0.11A, because the PNP transistor now had to switch four transistors instead of three. Basically I got a little bit worse results compared to the 2n3055 transistor, bat I think that this is because now the circuit had to open and close four transistors in parallel thus consuming more current. After all both transistors are working just as good and we can safely say, that the problem is not th the transistors used. In test number 3 I used a light bulb in the output and the 2n3055 for switching. This time I got lower voltages and overall efficiency. And in the last test I attached a 10000uF cap in parallel of the bulb in the output, this increased the efficiency a little bit. Here are the results:
Test1

Test2

Test3

Test4


Any comments, suggestions?
Thanks,
Jetijs
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  #463  
Old 12-07-2007, 09:11 PM
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elias elias is offline
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Quote:
Originally Posted by Jetijs View Post
Are you talking about the motor I am working on? If so, then you have missed, that we already have an independent frequency of the pulses regardless of the RPM's of the motor. The switching is done by a 555 timer.
Yes and that's nice, but you didn't mention the frequency at which you pulsed your coil? My test data shows that there is a frequency for any coil that the efficiency gets maximized. Have you attempted to adjust the frequency of your pulsing? I have been able to get about 80% back with those coils, but maybe larger coils don't put back as smaller ones do. I'll do more experiments with different coils and see what happens.
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  #464  
Old 12-08-2007, 04:53 AM
Peter Lindemann Peter Lindemann is offline
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Great Work

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Originally Posted by elias View Post
Yes and that's nice, but you didn't mention the frequency at which you pulsed your coil? My test data shows that there is a frequency for any coil that the efficiency gets maximized. Have you attempted to adjust the frequency of your pulsing? I have been able to get about 80% back with those coils, but maybe larger coils don't put back as smaller ones do. I'll do more experiments with different coils and see what happens.
Elias,

Thanks for running these tests. I have been saying that I thought 80% recovery was both possible and the goal of this project. If the motor can recover 80% of its input electrical energy AND produce 80% mechanical energy at the shaft by careful timing and small air-gap, then the motor should be able to operate with a COP=4.

Your tests show that 80% electrical recovery is possible with proper switching.

Thanks again,

Peter
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  #465  
Old 12-08-2007, 09:44 PM
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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
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  #466  
Old 12-09-2007, 02:22 AM
nali2001 nali2001 is offline
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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
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  #467  
Old 12-09-2007, 03:51 AM
Peter Lindemann Peter Lindemann is offline
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Core Material

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Originally Posted by Jetijs View Post
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
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  #468  
Old 12-09-2007, 03:57 AM
Peter Lindemann Peter Lindemann is offline
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How is your motor?

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Originally Posted by nali2001 View Post
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
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  #469  
Old 12-09-2007, 12:23 PM
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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
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Old 12-09-2007, 05:46 PM
Peter Lindemann Peter Lindemann is offline
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Moving On

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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
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  #471  
Old 12-10-2007, 02:17 PM
nali2001 nali2001 is offline
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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
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Old 12-10-2007, 02:41 PM
nali2001 nali2001 is offline
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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
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Last edited by nali2001; 12-10-2007 at 10:31 PM.
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  #473  
Old 12-10-2007, 09:12 PM
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Jetijs Jetijs is offline
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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
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Old 12-11-2007, 06:11 PM
Peter Lindemann Peter Lindemann is offline
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Thanks For The Up-date

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Originally Posted by nali2001 View Post
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
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Old 12-11-2007, 08:10 PM
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Jetijs Jetijs is offline
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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
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Last edited by Jetijs; 01-18-2008 at 01:33 AM.
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Old 12-11-2007, 08:47 PM
Peter Lindemann Peter Lindemann is offline
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An Idea...

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Originally Posted by Jetijs View Post
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
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Old 12-12-2007, 11:52 AM
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Jetijs Jetijs is offline
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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
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Last edited by Jetijs; 12-12-2007 at 01:01 PM.
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  #478  
Old 12-12-2007, 01:18 PM
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lighty lighty is offline
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Quote:
Originally Posted by Jetijs View Post
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.
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  #479  
Old 12-12-2007, 02:34 PM
nali2001 nali2001 is offline
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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
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Last edited by nali2001; 12-12-2007 at 02:40 PM.
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Old 12-12-2007, 03:48 PM
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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.
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