Mostly PM motor - Joe Flynn motor. My attempt to replicate

[Jetijs]

I am sorry for two things Jetijs...
1) I am profoundly sorry to barge into your most excellent innovation.
2) I am sorry for your workroom loss.

Now on to better things. Have you given the thought to using a rodin coil to energize your magnetic switches? it would take some redesigning of the cage but it could be done. The Rodin coil can energize the switches with less current since it has 60% more magnetic interaction inside of the coil then a standard coil. Just a thought. If you haven't read about it there is a forum post about the coils on here. It might be an interesting read for you?

No need to be sorry
Yes, I know about Rodin coils. I have wound several dozens of them myself
But the problem in using them on parallel path motor is the limited space and the stator shape, I can not imagine how one could wind a Rodin coil on a stator shaped like that
Thanks,
Jetijs

[gotoluc]

Luc, I tried your approach for the recovery with the cap and adjustable resistor as load. Does not work. No matter what value resistor I use, the current consumption goes up. The less resistance, the bigger the change.

Jetijs

Hi Jetijs, thanks for letting me know

If this is the case, then I would suspect that flyback is used in this motor design

Luc

[Jbignes5]

No need to be sorry
Yes, I know about Rodin coils. I have wound several dozens of them myself
But the problem in using them on parallel path motor is the limited space and the stator shape, I can not imagine how one could wind a Rodin coil on a stator shaped like that
Thanks,
Jetijs

Well it was worth mentioning since you are well respected here.

Like I said you would have to redesign the lobes and change the rotor. It would not be as compact, in fact the larger the rotor the better the torque. Looking at your rotor I see one thing happening that might not be wanted and thats crossing the fields thru the rotor. Changing the rotor to a much bigger radius and making it plastic with steel laminations would make the torque even better.
The rodin coil was just a side note. unless your coil cores are further out you would not be able to do it with your current setup. Oh by the way I am very impressed with your building skills. Quite professional!
Could you drop by the magnacoaster thread and look at that? I am interested in what you think about it, your take on it.

[zhorv324]

Thanks Jetijs for oscilloscope shots. In first hand I think that driven pulse off your motor have wrong shape. Reason maybe different but I suspect the problem is saturation off core (big magnets) . But you will see changes when you replace magnets.Yes another thing if you built new controller (full bridge) you mast use separate supply for electronics because you have common ground and that is problem. Anyway god lack with controller

[Michelinho]

Hi all,

Have you tried an air gap on magnets by inserting a tin layer of paper on each sides. Worth a try before deeper changes.

Take care,

Michel

[zhorv324]

Today I surf on Internet and found this picture on, jnaudin. free fr. If you look closely this oscilloscope shot have same characteristics as yours. Only difference is duration and shape of driver pulse. Triangle belove described as captured bemf.

[Jetijs]

Hello everybody!
I have an update. I received the magnets today, they are 1"x0.5"x1/4" So that four of them make a 1"x1"x0.5" magnet of half the size of the previous setup.
I made two tests, one using the old setup with big magnets and other using the new smaller magnets.
In the first test using big 1" cube magnets the motor ran:
at 2492 RPM using 12.0V at 2.1A
and
at 4660 RPM using 25.0V at 2.1A.

In the second test using those smaller magnets the motor ran:
at 2260 RPM using 12.0V at 0.95A
and
at 4248 RPM using 25.0V at 0.95A.

Both tests were performed with no load.

So I lost some RPM's but the current consumption also went way down by about 55%. The torque feels a bit smaller and it takes a little bit more time for the motor to reach max RPM's
I guess that these magnets are a bit too small to fully use the core saturation potential, that is why there is less torque. Also I am now using 55% less current so also the electromagnetic force is less and this is also a reason for smaller torque. But hey, the goal is to use as small power as possible to make the magnets do all the work
Will make the scope shots now.
Thanks,
Jetijs

[zhorv324]

Hi Jetijs ,I'm happy to see that your work on motor is still continue. As I say before size of magnets have great influence in current consumption . Now your magnets is 2x smaller and current consumption is of course smaller. In every setup you need to reach certain number of amperturns witch depend of size of magnets and core (saturation) . Torque also depends of magnets size and amperturns (sum of flux). You only need to find same balance between size of magnets , core saturation and coil (not easy) .

[Jetijs]

Thanks zhorv324

Here are the scope shots:
This is a shot across drain and source of one of the MOSFETS:
http://www.emuprim.lv/bildez/images/...oltage_31v.jpg

This is the current waveform on a shunt at one of the coils when motor is running at 12v:
http://www.emuprim.lv/bildez/images/...urrent_12v.jpg

This is the same, but at 31V and higher speed:
http://www.emuprim.lv/bildez/images/...urrent_31v.jpg

This is the current waveform on a shunt on the + side of the power supply at 12v:
http://www.emuprim.lv/bildez/images/...__line_12v.jpg

And this is the same at full speed (31v):
http://www.emuprim.lv/bildez/images/...__line_31v.jpg

I have yet to receive the torque meter to get the efficiency data.
Thanks,
Jetijs

[zhorv324]

Oscilloscope shots are different .Tell me Jetijs, did you tray to change time of switching ( don't think duty cycle) put advance or late. I think that maybe worth to tray. This is connected with magnetic remanence in silicon steel ( at least I think) . And finally I by second hand oscilloscope Its nothing special but serve to me

[Jetijs]

zhorv324, congrats on your new scope

I did not change the timing on my motor when I took the scope shots. I noticed that they are different so after the test I tried to change the timing, but it was already at the best position with the max RPM, so the change in scope shots is not because of the timing
Jetijs

[zhorv324]

Thanks Jetijs . Idea of changing time in advance is not completely mine ,guys from Italian forum experiment with this. They explained that was necessary when motor are load. I tray few things but result is not same every time .Maybe I cant provide same amount of load in experiment and in that time I don't have oscilloscope to see change in wave form. Anyway god lack with experiment . Pleas tell me if you have any progress with full bridge controller .

[Jetijs]

Hi zhorv324
I will make some experiments wit changing the timing depending on the load. Sounds promising
I still have not started the work on the full bridge circuit because there are some parts in that circuit that are not easily obtainable in my country.
I will let you know about my progress.

Thanks,
Jetijs

[zhorv324]

Hi Jetijs .I attach one picture who explain problem with timing. Picture is from my old school book and explain difference between rotor and stator position and attraction force. As you see last 15 degree attraction force is almost zero , ,and yet rotor mast spin next 15 degree before next impulse is come. Of course this is normal for all impulse motor but i like avoid that gap in torq. You can see that if you change input voltage to very small value and hold rotor with fingers. There are two ways to avoid problem, one is changing switch time and another is changing geometry of motor. I think that changing switching time is easy way Anyway god luck with experiment.

[Jetijs]

Ok, I think I understand you
Thank you for the explanation