Electric Motor Secrets

[lighty]

Peter, lighty,
of course I tested the bearing holders before I increased the air gap. I could not feel any movement in them, the they are holding the bearing rock solid.

Of course they're holding bearings rock solid but maybe they're slightly misaligned? Ah well, you already increased airgap so what's done is done. BTW- have a little patience those parts I've sent you entered Latvia on 18.03. so you should get them any day now- then you can use updated electronics as well.

[Jetijs]

Peter, lighty,
of course I tested the bearing holders before I increased the air gap. I could not feel any movement in them, the they are holding the bearing rock solid. Also I am now convinced that the shaft is not bending. The shaft is made of non magnetic stainless steel and is 10mm in diameter in the thinnest point (the shaft ends are thinner, but that does not affect anything). So I gave the rotor to engineers to increase the airgap. They took off a whole of 0.1mm form the diameter. That is 0.05mm on each side. This gives an air gap of 0.13mm on each side. But now I don't have any surface touching problems anymore. Unfortunately something in my transistor board has fried, today I tried to run the motor but nothing happens. I checked the optoswitches - they are ok, something else is wrong. The motor gives no sign of life. I can increase the input voltage up to the max, but there are no amps flowing. I double checked everything, but found nothing. I will have to make a new circuit board just like before with my first motor But I made a test without commutation and it seems pretty nice. Here is a small video:

YouTube - Lindemann attraction motor V2.0

You can see that the motor has a great potential and with a mechanical commutation the motor would just fly away. That bump sound on the beginning of each impulse is because I can not make the power pulse short enough, so that the rotor can not get past the fire zone and is pulled back. Only once in the video you can see a pulse without that bump. I also thought about the transistors. In order to get the max performance, I need them to open fully, because when they are not fully opened, there is a big voltage drop across them and much energy is wasted into heat. If the transistors would open fully, there would be much less heat. I will take this into account when soldering my new circuit board.

Happy easter BTW

Thank you,
Jetijs

[lighty]

Steel cannot be compressed in the way you suggest without serious bending of material. And I suspect that if Jetijs glued plates together and bolted them properly the stator can't be bent the way you suggest.

[Jan H]

just another theory

Jetijs,
I know this looks like it could never happen, but have you considered this?

the magnet force is in my opinion unlikely to offset the rotor itself, because it pulls in both directions. But the force of the magnet might be bending the armature ever so slightly. Steel is very flexible, and due to the tolerances worked with this could be the cause.

I'm no expert but just another idea i'd like to toss in. We all want you to succeed

[Peter Lindemann]

I Agree

@Jetijs

Is it possible for you to measure possible bending of shaft? It could be that your shaft is imperfect or that you assembled rotor (or stator for that matter) a bit "off" of certain points along the length of motor.

How thick is your shaft and what material did you use? I doubt that your motor can produce so powerful magnetic pull to bend the shaft if you use any standard quality steel with appropriate shaft diameter.

Also, are you sure that your bearing case don't introduce any lateral movement? Maybe the bearing casing is too lose or have too much tolerance?

You really ought to check out everything before widening air gap because once you do it there is no going back.

Jetijs,

I totally agree with Lighty here. Take your time and check each gap from both ends. It may be that one bearing holder is slightly better aligned than the other. You are at the point where engineering and "massage" overlap! Lighty is right. Only take non-reversible actions as a last resort.

Peter

[lighty]

@Jetijs

Is it possible for you to measure possible bending of shaft? It could be that your shaft is imperfect or that you assembled rotor (or stator for that matter) a bit "off" of certain points along the length of motor.

How thick is your shaft and what material did you use? I doubt that your motor can produce so powerful magnetic pull to bend the shaft if you use any standard quality steel with appropriate shaft diameter.

Also, are you sure that your bearing case don't introduce any lateral movement? Maybe the bearing casing is too lose or have too much tolerance?

You really ought to check out everything before widening air gap because once you do it there is no going back.

[Peter Lindemann]

Gaps

Peter,
I made a new commutator wheel with one 40 degree gap on each side. This did not make any improvement. I noticed, that the motor can not even make one revolution, because it always locks in the same position each time. I turned on the power and listened to the shaft movement, the hissing sound was there on the same spot, when the rotor locks. I took a thickness gauge sheet 0.04mm thin and tried slipped it between the stator and rotor on various places. I found one place where it was much harder to slip through, but it could be done. I am starting to suspect that the shaft may bend on each pulse a little bit and if the pulse is on the spot where the stator and rotor is almost touching, then both surfaces lock together and no movement is possible. Because if the shaft would not bend I should not be able to get the thin metal stripo between the surfaces on the lock zone. I don't think that the stator is moving between the plastic end plates, also the bearings are high quality two row bearings (they cost me about 30$ each). Any suggestions? I guess that I will have to increase the air gap a little bit

Jetijs,

The motor I have at my shop currently runs on a circuit very similar to this. It is capable of high speed operation with no problems EXCEPT it tends to "suck the gaps" under high power. Unfortunately, my old Flux-Motor frame has movable stator cores and keeping them stable is a mechanical problem that I have not solved yet.

If you are satisfied that the stators don't move, then fine. I agree with Steven that the probability that the shaft is flexing is very low, since the magnetic forces are balanced from side to side in your design. I agree with you and think that opening up the air-gap a little bit will solve the binding issue. Start by taking a total of .001 inches off the diameter of the rotor (.0005 inches per side) and see if that is enough.

Peter

[nali2001]

Idea

Hi there Jetijs,
Well I'm not really sure how thick you rotor axle is but I don't believe it will bend unless much more power used. In fact one way of testing is running the motor on much lower power. So that there is less magnetic strength going on. So it is highly doubtful that at low power the axle will 'still' bend. It does seems more like some strange switch/timing problem. Also with my device the timing was at some points very critical I could at one time, time it go get high speeds, but then it would not start at all. Or just start reversed. What you could do is, remove all the electronics and just make some simple contact points or mega simple commutators that will just make and break the coil - to - battery connection. Like:
http://www.gcsescience.com/Split-Ring-Commutator.gif
http://www.bcscience.com/images/stlouis_commutator.jpg

Regards,
Steven

[Jetijs]

Peter,
I made a new commutator wheel with one 40 degree gap on each side. This did not make any improvement. I noticed, that the motor can not even make one revolution, because it always locks in the same position each time. I turned on the power and listened to the shaft movement, the hissing sound was there on the same spot, when the rotor locks. I took a thickness gauge sheet 0.04mm thin and tried slipped it between the stator and rotor on various places. I found one place where it was much harder to slip through, but it could be done. I am starting to suspect that the shaft may bend on each pulse a little bit and if the pulse is on the spot where the stator and rotor is almost touching, then both surfaces lock together and no movement is possible. Because if the shaft would not bend I should not be able to get the thin metal stripo between the surfaces on the lock zone. I don't think that the stator is moving between the plastic end plates, also the bearings are high quality two row bearings (they cost me about 30$ each). Any suggestions? I guess that I will have to increase the air gap a little bit

[cdsalmons]

HERE I hope this can help someone, Dustin

[lighty]

@nali2001

Your schematic is pretty much the same as the basic one I use although I do use some other tricks to improve switch-off time and reduce oscillation of MOSFETs during shut off and I added several means of protecting both MOSFETs and drivers should anything go wrong (overvoltage for example).

Last week I sent Jetijs a few fast power MOSFETs, advanced MOSFET drivers (with enable pins which are to be used for gating switching signal) as well as some optocouplers and hyperfast diodes, protection diodes, various resistors, trimmers etc. He should get it by the end of this week or during next one at the latest.

Improved components and schematics should make experimenting easier and performance better.

[nali2001]

Hi there Jetijs,
First thing I would like to compliment you on your great work and persistence. It is really rare to see someone go to such effort in this field. Sorry to 'hear' about your recent problems. I very much doubt that the rotor is touching the stator, if that were to happen you would certainly hear it clearly and there would be much vibrations and violence going on. One method of knowing is to paint the poses of the stators with some recognizable color, run the motor, and disassemble it again, if the paint is scraped you have found your problem. I see that it indeed does not run that fast and to me it does seem like some kind of switching problem. Personally I am not too much of a fan the way you are driving the thing.
Here is my circuit. http://www.krystyna.nl/Machine/Circuit001.gif It uses a fet driver and mosfets. It really is not all that complicated. Just a few cheap parts.

Kind regards,
Steven

[Jetijs]

Just so that you know I will post how I assemble this thing. First I take the stator and insert the rotor into it. Then I use thin metal sheets used as thickness gauges. I take four of them and slide them between stator and rotor, two sheets on each side. 0,08mm thick sheets are rather hard to push between stator and rotor, but it can be done. This ensures that the air gap is even from both sides. Then I press the stator between the two plastic end plates so that it fits into the 2mm deepening. The stator is a tinny little bit smaller than the deepening of the end plates, this can make the stator move a little between the endplates at very powerful motor pulses. This is what I mean:



The only thing that holds the stator in place is the pressure that forms when the end plates are bolted together, but if this pressure is not high enough, the stator can move up and down between the plates for about 0.5mm.
So, I bolt the plastic end plates together and then I fix the bearing block, bolting it to the plates. In theory this should be precise enough and all I have to do now is simply to pull out the metal sheets between the stator and rotor and the rotor should remain in perfect position. But in reality it is not as simple. When I pull those sheets out, the rotor wont rotate freely, it will touch the stator at some point. Then I do the following, I turn the rotor back and forth to get the feel when it touches the stator, then I tighten one of the four bolts that holds the end plates together a little bit. If I feel an improvement, I continue tightening the bolt till I feel that it starts to go worse. Then I do the same thing with other three bolts and bit by bit tighten them to the best position possible. When this is done, I simply tighten the remaining "inner" nuts so that the position is fixed steady. Unfortunately I can not get the gap just right, there will always be that quiet sound, that indicates that the rotor is touching the stator so slightly that you can not even feel. I can just adjust everything so that this sound is as short and small as possible. I think that the only way to solve this would be increasing the gap slightly, but lets leave that for later.

I hope you understood what I mean
Thanks,
Jetijs

[Peter Lindemann]

Check the Air-gaps

Yes, Peter, I just cut off the slots
I will make a new commutator wheel tomorrow and see what it does. The plexiglass end plates are bolted together rather hard, I do not dare to tighten the bolts harder because I am afraid that the glass could crack. The last thing what I did today was removing the circuit from the motor and then just hit the coil terminals on a battery. I noticed, that if I did this with one phase, the rotor would spin violently for several revolutions. But if I did this with other phase, it spins for only one revolution and the spark at the battery terminals is greater. Might it be that there is a much smaller air gap on the second phase and this makes the rotor to lock on the power pulse? Because you can't really see what happens, because it happens so fast.
Ok, now for the commutator wheel and then we will see

Thank you,
Jetijs

Jetijs,

See if you can slide a thin piece of paper in between the rotor and stator. Check each stator with both sides of the rotor. Its possible that everything is fine, EXCEPT that the bearings are just not quite centered. This could account for one gap behaving differently. You might have to shim the bearing positions a tiny bit.

I agree with you. Don't try to tighten the frame anymore than the plastic can handle.

There also might be an electrical problem with the second coils. Check the resistance of the coils and make sure they are isolated and measure the same resistance as the other set.

Just go through everything methodically. You'll find the problems and fix them.

Peter

[Jetijs]

Jetijs,
It sounds like you are making a rapid set of changes to the machine without carefully considering the consequences. I assume your commutator wheel with the 65 degree opening was made by cutting the slots off of the slotted wheel. Yes, No?
Peter

Yes, Peter, I just cut off the slots
I will make a new commutator wheel tomorrow and see what it does. The plexiglass end plates are bolted together rather hard, I do not dare to tighten the bolts harder because I am afraid that the glass could crack. The last thing what I did today was removing the circuit from the motor and then just hit the coil terminals on a battery. I noticed, that if I did this with one phase, the rotor would spin violently for several revolutions. But if I did this with other phase, it spins for only one revolution and the spark at the battery terminals is greater. Might it be that there is a much smaller air gap on the second phase and this makes the rotor to lock on the power pulse? Because you can't really see what happens, because it happens so fast.
Ok, now for the commutator wheel and then we will see

Thank you,
Jetijs