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Author Topic: Permanent magnet assisted motor coil designs  (Read 19189 times)

Offline captainpecan

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Re: Permanent magnet assisted motor coil designs
« Reply #180 on: April 22, 2022, 08:01:09 AM »
Okay, I reversed the changes I made, and did some more tweaking of things. Interesting enough, it actually performs better with a little wider gap between stator and rotors. I ran some tests and kept making small changes until I got the best result. I guess having all like poles on the rotor needs a bit more gap to get clearly defined separate poles for best performance. At least that appears to be the case.


Now, I am noticing if I completely disconnect 2 of the 3 coil pairs, I get better performance from an individual coil pair. I also get much cleaner scope readings and way stronger fly back spike. As was suggested helping me understand weird readings on the scope, I am getting some feedback from the other coils effecting each other. This is really hurting the performance. I need a better motor driver circuit or a better way to isolate each mosfet. I am thinking of ordering the parts to build a motor driver circuit that was posted earlier in this thread. Does anyone have any good ideas of a simple way I can stop some kind of random feedback I am getting with my circuit? I have it posted above. The problem occurs when more than one reed switch is closed at the same time. Something is looping back and I can't seem to easily nip it in the butt. Any suggestions appreciated.

Offline gyulasun

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Re: Permanent magnet assisted motor coil designs
« Reply #181 on: April 22, 2022, 06:53:58 PM »

On your post #179: Can it be that the steel material you added to reduce the gap introduced unexpected eddy current loss?   

Now that you reversed the changes as you wrote in reply #180 and have some better results you noticed that a single coil pair gives better operation than 3 pairs together, this is the next step to find out why.   
Try to reduce the supply voltage to say 3-5 volts only for ALL the 3 MOSFETs and see whether the problem occurs at such low levels. If the problem is not present, then try increasing the supply voltage gradually.   
If the problem is present at the 3-5 volt supply, then run one switch only for one coil pair from say 12V supply and if this operation is acceptable, then use a 2nd MOSFET switch from 3-5 V supply only if you can and see whether the problem comes up already.   

You did not mention whether you changed for instance the 10 k gate-source resistors to say 1 kOhm?   
I do not say this is the problem, perhaps just an additive to  it.  Remotely is hard to comment.

Offline captainpecan

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Re: Permanent magnet assisted motor coil designs
« Reply #182 on: April 22, 2022, 11:36:18 PM »
I will be working on it some more tonight, so I'll try and narrow things down like you mentioned. I did forget to mention that i did change resistors to the gates. I was a little surprised no change at all. Not even current draw. But that was before I noticed there is interferance between coils anyway. As soon as I only connect 1 coil pair, the flyback over doubles and looks more normal. So until i fix that interferance, I'm not even sure the changes would have shown anything to me anyway. I would like to build a circuit citfa shared with me here but I'm short a few components. I think I will take inspiration from it and try putting each coil pair between 2 mosfets. Maybe it will better isolate each set of coils.

Offline captainpecan

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Re: Permanent magnet assisted motor coil designs
« Reply #183 on: April 23, 2022, 10:53:16 AM »
Well, I got a little further. I was only able to find 1 P channel mosfet to use so I could only try on 1 coil until I cam find more or figure the proper way to use 2 N chanel instead. But I simply put my coil between a P chanel and an N chanel. Each with a resistor pulling them up or down. I put a reed between the gates. It works very well and a nicer sharp pulse with a solid strong fly back. I now am able to see a current increase and decrease as I adjust resistance on the gates as suggested earlier. I think I may have the solution that will work for me and I am still able to use bare minimum current. Hopefully. Fingers crossed. Now to get my hands on some P chanel mosfets or find the best way to use all N chanel so I can see if all 3 pairs work in unisom without interferance.

Offline Cadman

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Re: Permanent magnet assisted motor coil designs
« Reply #184 on: April 23, 2022, 01:22:45 PM »
Well, I got a little further. I was only able to find 1 P channel mosfet to use so I could only try on 1 coil until I cam find more or figure the proper way to use 2 N chanel instead. But I simply put my coil between a P chanel and an N chanel. Each with a resistor pulling them up or down. I put a reed between the gates. It works very well and a nicer sharp pulse with a solid strong fly back. I now am able to see a current increase and decrease as I adjust resistance on the gates as suggested earlier. I think I may have the solution that will work for me and I am still able to use bare minimum current. Hopefully. Fingers crossed. Now to get my hands on some P chanel mosfets or find the best way to use all N chanel so I can see if all 3 pairs work in unisom without interferance.
Hi captainpecan,

Now you are talking about something similar to what I have been experimenting with all winter. Charging a coil between 2 mosfets, disconnecting the coil and at the same instant reconnecting it to a separate circuit before the field can collapse in order to collect the inductive discharge as a separate entity. I think this method has a lot of potential.

So far, due to my non-existant electronics skills,  I’ve fried a ton of both P&N mosfets so, please, if you would share any circuits for this I sure would appreciate it.

Regards

edit: I mean any circuits you use with your experiments on this thread..



Offline gyulasun

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Re: Permanent magnet assisted motor coil designs
« Reply #185 on: April 23, 2022, 09:01:11 PM »
Hi captainpecan,

Now you are talking about something similar to what I have been experimenting with all winter. Charging a coil between 2 mosfets, disconnecting the coil and at the same instant reconnecting it to a separate circuit before the field can collapse in order to collect the inductive discharge as a separate entity. I think this method has a lot of potential.

So far, due to my non-existant electronics skills,  I’ve fried a ton of both P&N mosfets so, please, if you would share any circuits for this I sure would appreciate it.

Regards

edit: I mean any circuits you use with your experiments on this thread..
Hi Cadman, 

I put in bold your sentence above I want to ask on:  have you attempted to connect a full wave diode bridge permanently across the coil the 2 MOSFETs were switching and direct the flyback spikes into either a capacitor or to your other circuit to utilize it?  I mean that in many cases no need for switching the flyback spikes by a dedicated switch which would need to be switched on at the moment the two MOSFETs are just switched off if you meant that?

See the attached drawing member citfta uploaded here https://overunity.com/19040/permanent-magnet-assisted-motor-coil-designs/msg564982/#msg564982  what I modified by adding a full wave bridge + a puffer capacitor.  The DC output is quasi fully isolated from the full switching circuit, the "quasi" means the body diodes of the p and n channel MOSFETs which are in reverse direction between the input supply voltage and the input of the diode bridge so the load at the output of the diode bridge normally cannot interfere with the supply voltage. 
An important note would be that in case there is a light load (i.e. a high impedance) across the DC output of the diode bridge then the flyback pulse amplitude may go high and may approach the breakdown voltages of the p and n channel MOSFETs, and can destroy them. So you should apply a relatively "heavy" load which is able to keep the flyback peak amplitude at a voltage level safe for the breakdown voltage ratings. 
The puffer cap need to have at least 200 V DC rating or higher and uF value may range from say 47 uF to 470 uF or higher. 
Note that this solution involves rectifying any induced voltage the coil may get in a particular motor setup whenever the 2 MOSFETs are switched off and those induced voltages are also collected in the puffer capacitor (this may involve a Lenz drag!).   When this is unwanted, then indeed a separate switch is needed and controlled in the needed manner if possible at all.
Note also that the MOSFET types in the schematic have only 100 V drain-source breakdown ratings so it would be advisable to use at least 400- 500 V rated types or even higher, depending on the Vcc supply voltage too.

Offline captainpecan

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Re: Permanent magnet assisted motor coil designs
« Reply #186 on: April 24, 2022, 01:32:28 AM »
Yup, that's the circuit I used for inspiration to do what I am doing now. I only had 1 P channel mosfet until more come in so I could only use it for 1 coil pair. I'm missing parts to complete it for now, but using a reed works great so far. I have also adapted it to use both N channel of which I have 100's of literally. I'm playing with it, but using 2 N channel so far gives me less performance and less fly back. But if I can't get it figured out, I'll have more P channels on monday.

Offline Cadman

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Re: Permanent magnet assisted motor coil designs
« Reply #187 on: April 24, 2022, 04:26:37 PM »
Thanks gyulasun and captainpecan.

The circuit I used is almost the same, except I used separate transistors to trigger the mosfets at the coil instead of a single trans, and a optocoupler for the signal. P-mos on the high side and N-mos on the low side of the coil. I've used a bridge on the flyback side and also tried individual diodes at the coil ends. So far having separate triggering transistors and resistors hasn't accomplished anything note-worthy.

All the mosfets and diodes are 600V 6A or better and diodes are UF type. 5V control for the transistors and 15-18V for the mosfets. The highest spike is right at 179V. Oh, and the cap collecting the discharge is a 400V 3000uF cap scavenged from a VFD.

I guess what this means is the problem is somewhere else in my circuit. Good to know.

If it ever amounts to anything I'll open a thread for it.

Thanks again guys

Cadman

Offline captainpecan

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Re: Permanent magnet assisted motor coil designs
« Reply #188 on: April 25, 2022, 07:43:09 AM »
Still waiting on some more P channel mosfets, so kind of slowed down my build a bit. But decided to work on a generator side of things while I wait. I wanted to choose a design I can easily couple to my motor, and be able to use it on a small wind turbine to play with if I want to. I have many odd ball ideas I want to try that this design is a good starter for. Since I have some nice strong neo magnets 60mm by 10mm bars, I chose a dual axial flux design again. Just basically like many wind turbine home builds. Seems to be a good fit for this project.There will be 2 rotors with 12 magnets on each, and a 9 coil stator sandwiched between them. I can make it relatively thin, and useful. I am bringing all coil leads out so that I can wire it in any way I wish to test things out. Here's how far I got today.

Offline captainpecan

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Re: Permanent magnet assisted motor coil designs
« Reply #189 on: April 25, 2022, 08:10:06 PM »
While I am waiting on parts, I was playing with the gate resistance and watching rpm and current draw changes. While playing with the pulse alignment and stuff I started noticing something interesting.


For this set up, I am just using 1 coil pair, triggered between a P and N mosfet. I posted the circuit above that I drew. Very simple. But when I move things around a little, and when i send the pulse, I start getting a large flyback spike BEFORE the pulse. I mean, at the exact moment the pulse BEGINS I am getting a spike at times. Doesn't seem to be every single pulse, or my scope just isn't catching it. Possibly there is more interferance as I was seeing earlier and got help debunking it. But the way these coils are made with an internal permanent magnet, it does flip the field outward at the beginning of the pulse, and inward at the end. I have been hoping I can somehow see that flip on the scope. Is that possibly what I am seeing here? It is showing up more, the lower the resistance I put on the gates of the mosfets. That means a little more current, more rpm, but a faster switch on time I believe that could explain catching this spike. Does anyone have any other thoughts on this leading spike I am getting at times?

Offline captainpecan

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Re: Permanent magnet assisted motor coil designs
« Reply #190 on: April 25, 2022, 09:07:52 PM »
Here are two scope shots. The only change was 1 shot is using a 10k resistor on the mosfet gates, and the other uses a 1k resistor. Could this be showing up due to the spec difference between the P and the N mosfet?

Offline gyulasun

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Re: Permanent magnet assisted motor coil designs
« Reply #191 on: April 26, 2022, 12:17:59 AM »
Your CH1 is set to 2 V/DIV it seems and your scope probe is across the two series coils, right?   
Would like to ask what was your supply voltage feeding the setup when you took the scope shots?   

Please also tell whether you have any load for the captured flyback?   

For the p and n channel MOSFET switch to work properly in this simple circuit, the supply voltage for their gate circuit should be way higher than the sum of their individual gate-source threshold voltages to be able to switch both on correctly.  Threshold voltage is around 4.5 Volt fet type dependent so at least a minimum of 10 Volt supply voltage should be fed across the two resistors the reed switch activates.   
The erratic switching at the "wrong place" may indeed come from the threshold voltage differences, how this is connected with the lower value gate-source resistances is not clear yet, (resistor tolerances and voltage division) if the supply voltage is too low, they cannot switch properly due to the poor DC bias, this may be one reason.   
You can always separate the drain voltage supply to the MOSFETs from the resistors supply so that the latter would get say at least 10-11 volts while the MOSFETS with the coils could get a lower voltage supply if you wish to avoid higher spikes developing now. 
EDIT It is possible the scope settings did not consider the 10x probe and 20 V/DIV is involved?  So you have about 12 V supply voltage...
   

Offline captainpecan

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Re: Permanent magnet assisted motor coil designs
« Reply #192 on: April 26, 2022, 01:34:15 AM »
It's all done from the power supply set at 16v. I have been having issues getting the scope set correctly. It seems the autoset feature keeps showing wrong for the v. I have something set wrong. But the wave is correct. I needed to unplug the scope and let it set again. But it is 16v supply. I'm still learning the scope settings.

Offline gyulasun

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Re: Permanent magnet assisted motor coil designs
« Reply #193 on: April 26, 2022, 09:59:57 AM »

I think you would need to choose manually in the Menu of CH1  the x1 or x10 etc multipliers when your probe is set to x10 and not 1:1.  The correct amplitude settings can be checked by measuring the square wave test amplitude with the probe and see the displayed amplitude and compare it to the one written under the test pin output on the front of the scope. (maybe it is 5Vpp)

When you have the 1 kOhm resistors in the circuit, hook up one probe GND clip to supply negative and the probe tip to the gate pin of the p channel MOSFET.  And hook up the other probe tip to the gate of the n channel MOSFET to see the switching waveforms.  The 16V should fall to around 8V on the gate of the p channel at the switch on moment of the reed and the zero voltage on the gate of the n channel MOSFETR should jump up to around the same 8V level when the reed is on. 
 Is it possible the reed switch is abused from earlier setups? If so the 8 mA current (16V / 2 kOhm) may make the internal contacts uncertain versus the 0.8 mA current (16V / 20 kOhm).  _This may not be a case but if you can replace this reed by another one, you will see.

Offline captainpecan

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Re: Permanent magnet assisted motor coil designs
« Reply #194 on: April 26, 2022, 02:24:52 PM »

Thanks again for all the help from you guys as I learn moving forward!


Oh, there is no doubt in my mind the reed switches have been abused. I'm waiting on some more. I have had to thump them a few times already after realizing my circuits weren't working right. They are working properly in general enough to run with them since im out of replacements and my other glass ones were junk from the factory. But at a micro level such as that, I need to replace them all. I've kicked their butts accidentally during my learning curve.  I will revisit this subject after I get more and swap them out. I did get my P channel mosfets and my spring scales. After a quick throw together, I got all 3 coil pairs firing as they should. There is a nasty rats nest of wires so I will hopefully solder up my driver circuit tonight and start preparing for an efficiency test after a little more tweaking. I would like to know if I am actually seeing some benefits from these coils or if i need to make some design changes again. Maybe I'll at least know if it is moving in the right direction. I would like to know if I've built a 25% efficient motor or if it's actually showing promise.


I need to shoot a quick video of some findings I had testing out my recovery circuit while I waited on parts. But I've got to clean up the rats nest of wires I have everywhere first so you can at least tell what is being filmed. I've got a few ideas for helping with Lenz on the generator side I can't wait to test. But 1 step at a time picking apart each phase so I can learn as much as possible!