Pierre's 170W in 1600W out Looped Very impressive Build continued & moderated

[pmgr]

Hi Luc,

I think Mosha points out the problem:
The number of magnetic half poles have to be an even number as magnetic fields always curls back forming loops. This is a problem in your stator! It is a 1.5 poled stator as it has 1.5 pole sets. Thus a return path for the last pole is missing or actually 1.5 poles are missing if making a three poled stator.

Regards
Ole

Ole, that is not correct. Take a look at the H-bridge image from before (with red and black wires) and the one below. One LED in Luc's setup controls 1 H-bridge. Each H-bridge makes a connection to +Vss with red output and to GND with black output. So even though you only see 3 LEDs on, 6 connections are made (three to Vss and three to GND).


See the image below when H-bridges 1, 11 and 21 are on: all 6 poles are activated in this case in opposite directions from eachother.


The only thing I can think of is that maybe the frequency is too high for L/R coil times and iron stator/rotor, or coils where not connected properly on the stator (start and end of winding reversed, or coil put in while rotated 180deg. But I asked Luc this same question and he said he carefully paid attention to all this when assembling the rotor.


The other thing is that he was able to spin the small magnet without problem, so the only thing I can think of is that the current Arduino frequency is too high.


Luc, I suggest you upload the sketch with the potentiometer so you can change the frequency to a lower/higher one easily and see what happens with the output coil voltage (make sure to leave it open, no load). Changing the frequency you should see the voltage increase when frequency goes higher (until you hit the R/L cut-off frequency). Voltage should go down when the frequency goes down. I suggest playing with it in the lower frequency range like 1-20Hz or so.


Also, put the magnet back in and start at a low frequency and let it spin, then turn up the frequency to see when it cuts out so you know how high you can go in frequency before it stops spinning (of course the thing has some mass, so it will not be an exact cut-off but it will give you a ball-park value).
PmgR

[onielsen]

Hi PmgR,

See the image below when H-bridges 1, 11 and 21 are on: all 6 poles are activated in this case in opposite directions from eachother.


The only thing I can think of is that maybe the frequency is too high for L/R coil times and iron stator/rotor, or coils where not connected properly on the stator (start and end of winding reversed, or coil put in while rotated 180deg. But I asked Luc this same question and he said he carefully paid attention to all this when assembling the rotor.


The other thing is that he was able to spin the small magnet without problem, so the only thing I can think of is that the current Arduino frequency is too high.

That looks OK then.

I would suggest increasing the frequency as transformers and inductors have to have quite much inductance at low frequencies. The parasitic resistance of the wire becomes dominating which is just waste of power as heat. If using ferrite as magnetic conductor the frequency could be say 50kHz or more depending on ferrite type. This gives a very much higher power density. Just look at how light weight a several hundred Watts power supply of high switching frequency is compared to a 50Hz power supply of the same power. The high frequency requires less inductance of the coils. The motor stator can't take that high frequency but should be OK for perhaps 100Hz.

Regards
Ole

[gmolina]

Hi Luc, i think that little details can change everything, i see that Pierre stator winding is similar to the attached image, and your winding, look different.

Regards,

GM

[gotoluc]

Hi Luc, i think that little details can change everything, i see that Pierre stator winding is similar to the attached image, and your winding, look different.

Regards,

GM

I agree that looks more like Pierre's windings but your drawing does not explain how it is wound.
Can you explain more of what you think is going on?

Regards
Luc

[gotoluc]

I made 2 videos, the first one in English and the next in French.
These videos are to explain the coils firring sequence and what I believe to be the reason why there's next to no flux going through the center core coil.

English video: https://youtu.be/wnHXpeu-Szo

Fr. J'ai fait 2 vidéos, la première en anglais et la suivante en français.
Cette vidéo a pour but d'expliquer la séquence d'allumage des bobines et ce que je crois être la raison pour laquelle il n'y a pas de flux passant par la bobine du noyau central.

Video en français: https://youtu.be/b4io8wZCb-s