Author Topic: Active Pitchcontrol  (Read 199855 times)

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mbouwer

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Re: Active Pitchcontrol
« Reply #756 on: June 27, 2017, 03:54:58 AM »
Test with 2 coils: wire 0,5 mm  lenght 6 meter
                         wire 0,14 mm lenght 2 meter

With the three stacked magnets thickness 6 mm I get 0,1 volt at 100 r.p.m.
With the round magnets thickness 10 mm both coils show 0,5 volt.

How to proceed?
« Last Edit: June 27, 2017, 04:05:02 AM by mbouwer »

joestue

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Re: Active Pitchcontrol
« Reply #757 on: June 27, 2017, 12:47:16 PM »
for a concentrated pole design you need all of the magnets installed to get volts/hz out of a single coil without using a spectrum analyzer to isolate just a single frequency's magnitude.

and since they aren't all in phase, you will need to multiply the voltage you get out of a single coil, by the winding factor, which for a 40,44,46 magnet, 48 slot machine is 0.96 to 0.95

your 2mm thick magnets are about half as wide as they need to be, so you can take them and arrange them nn ss nn ss nn ss. a 2mm thick layer of magnets may be enough, 4 would probably be better. do you have enough magnets on hand for a 2 mm layer arranged nnssnnss? for a 40, 44 or 46 pole machine you would need 80,88 or 92 magnets.

they do need to be radially aligned perfectly far as i know. probably doesn't matter if one is out of place, but if half of them are a degree or two bunched together, you could have a lot of cogging torque.

you don't have near enough room for copper to effectively utilize the 10mm thick round magnets, doesn't mean you can't use them, its like installing a 400hp engine in a geometro. it doesn't weigh enough to effectively use the hp, but you can still burn the wheels out. but so would a 100 hp engine.

mbouwer

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Re: Active Pitchcontrol
« Reply #758 on: June 28, 2017, 07:19:57 AM »
48 slots.
So I can buy 46 magnets 20 x 18 x 5
They fit on the outer diameter of the rotor.
« Last Edit: June 28, 2017, 09:44:35 AM by mbouwer »

mbouwer

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Re: Active Pitchcontrol
« Reply #759 on: June 30, 2017, 04:39:56 AM »
2 mm layer arranged nnssnnss.......  I would like to apply. Enough magnets.
But nn and ss are repelling.

hiker

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Re: Active Pitchcontrol
« Reply #760 on: June 30, 2017, 10:50:03 AM »
Super glue..slide the two together and hold in place for 10-20 seconds ...small mags..super glue alone should be more than enough...made a few small mills with nothing but super glue holding the mags..they still work great...on my larger mills I used super glue and epoxy stick in the gaps between the mags to hold the mags in place..great product..shock proof..hard as rock...easy to apply..
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joestue

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Re: Active Pitchcontrol
« Reply #761 on: June 30, 2017, 06:36:46 PM »
I highly suggest you get it working with the magnets you already have. 2mm thick may be enough. Yes they repel each other but if you put a spacer between the nn and SS magnets, they will be forced to remain where they are supposed to. You could also machine the 46 slots you need for the magnets to sit in. The slot only needs to be .005" deep for the magnet to be stuck radially. It could however decide to stick to the stator instead so you still need some glue.

I don't recommend superglue.

mbouwer

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Re: Active Pitchcontrol
« Reply #762 on: July 02, 2017, 07:23:46 AM »
It seems a good idea to me to first enlarge the slots.
Then I can dispose more copper and use a coilwinder to shape the coils.

SparWeb

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Re: Active Pitchcontrol
« Reply #763 on: July 02, 2017, 04:47:11 PM »
It seems too late to say anything, but I wish you hadn't done that.
Opening up the slots makes it easier to insert the coils, but it also makes it easy for the coils to dislodge, striking the magnet rotor as it goes by.
It also removes much of the surface material that the magnet rotor passes, causing a stronger cogging effect.
Lastly, the machining of the laminations together causes them to re-connect electrically, because you've cut through the oxide barrier that separated them (even if it's just in the area you machined).  This could add a large number of eddy-current short-circuits that will just drag down the whole machine.
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mbouwer

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Re: Active Pitchcontrol
« Reply #764 on: July 03, 2017, 03:07:49 AM »
Thanks for your comments. New options: take apart the laminations to polish and paint.
                                                            locking up the coils with epoxy
                                                            search for a lamination core that is obtainable.

hiker

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Re: Active Pitchcontrol
« Reply #765 on: July 03, 2017, 11:02:26 AM »
the coils are attracted to the mags as they pass over...so be sure theirs no loose strands of wire that can dislodge...no fun having to rewire...been their !
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mbouwer

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Re: Active Pitchcontrol
« Reply #766 on: July 05, 2017, 05:33:28 AM »
Found a new lamination package and that opens up new possibilities.

hiker

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Re: Active Pitchcontrol
« Reply #767 on: July 05, 2017, 11:05:55 AM »
motor shop find ?  Nice...deeper slots as well..
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mbouwer

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Re: Active Pitchcontrol
« Reply #768 on: July 05, 2017, 12:06:17 PM »
At a firm that overhauls electric motors.
To become a larger inside diameter I want to cut away the teeth and make new slots. Now 1 sheet at a time.
Then polishing, painting and assembling.

mbouwer

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Re: Active Pitchcontrol
« Reply #769 on: July 06, 2017, 05:32:33 AM »
The 0,5 mm sheets are vulnerable and slack. I need a ridgid ring to fasten them.

joestue

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Re: Active Pitchcontrol
« Reply #770 on: July 06, 2017, 11:13:48 AM »
Cutting the teeth down marginally reduces leakage flux and increases the peak torque available from the machine, at the expense of increasing copper losses, however in your case you cut the tooth and your slot opening doubles or triples, probably negating any benefit.


anyhow, i made a concentrated, 30 pole 36 slot machine from a 1/6th hp induction motor using 1/8th inch thick magnets that were 2 inches long and 1/4th inch wide.

the air gap was fairly small, and the flux generated in the tooth by the magnets was on the order of 1.5T, which is mostly saturated. the machine could generate about 1/2 hp at about 75% efficiency, at 800 rpm and around 200hz, not bad in my opinion for 1.875 cubic inches of magnets. it had a 36 position cog because the air gap was not identical all the way around the rotor, and because one of the coils had a shorted turn, and because one of the magnets was 1.6 inches long instead of 2 inches.
« Last Edit: July 06, 2017, 07:10:32 PM by joestue »

mbouwer

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Re: Active Pitchcontrol
« Reply #771 on: July 07, 2017, 02:02:18 AM »
The professional direct drives give great inspiration.
Many slots, low speed, large inner diameter.
Until finding a suitable lamination core ( at a reasonable price) I think I need to shape it myself.


joestue

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Re: Active Pitchcontrol
« Reply #772 on: July 07, 2017, 08:15:52 AM »
It's fine the way it is.

Cutting the teeth down to increase peaks torque levels doesn't matter anyway because you can't operate it at that torque level for more than a few moments or the copper overheats.

read here
www.mdpi.com/2075-1702/4/1/2/pdf

So it is good to have wide open teeth, the reason why is because there is less leakage flux between the teeth. The problem is, it significantly increases eddy currents in the magnets. depending on what rpm and torque you intend to get, this may or may not be significant. 

from https://www.comsol.com/paper/download/199803/giacometti_paper.pdf you can find approximately the ideal ratio of slot tooth width to slot width. its about 1:1.6 to 2.  the ratio you find in traditional induction motors is about 1:1, or 1:1.5, but its not that bad. in a ceramic magnet motor, 10 poles, 12 slots, i found the ratio was about 2-3:1 (i could go measure it, but you're using neodymium, not ceramic magnets). there's basically twice the volume of copper as there is volume of teeth.

far as i know, ideally the depth of the slot is ideally the same as the width of the slot. but its not that much of a hit to stick with the traditional 2 or 3:1 depth to width ratio of the slot. basically you want to keep the magnetic flux lines away from the coil, and a good way to do that is fit all the copper in a 1:1 cross section. traditional machines have deep slots because the coils span several slots. when you look at the entire coil, the coil takes up a 1:1 cross section, but its spread out across at least 3 slots, each with a 3:1 cross section ratio.

I see no reason to increase the magnets beyond the number of slots, because the increased eddy current losses scale with the square of the frequency.. this is why its so much of a hit to cut the laminations.

some magnet to slot ratios are much worse than others at air gap harmonics. the 24 magnet 36 slot has much less eddy current losses in the core as compared to the 30 pole 36 slot, but the winding factor is .86 instead of .96. so its rarely a good choice.
« Last Edit: July 07, 2017, 09:16:09 PM by joestue »

mbouwer

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Re: Active Pitchcontrol
« Reply #773 on: July 08, 2017, 02:55:28 AM »
So I will use the lamation core in the form as it is now.
Made a new supporting ring.

mbouwer

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Re: Active Pitchcontrol
« Reply #774 on: July 09, 2017, 02:42:27 AM »
Only 3 spokes is conveniently because of the space needed to shape the coils. But the innerring should be more robust compared to the whole.
I want to try to make an improved version.

mbouwer

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Re: Active Pitchcontrol
« Reply #775 on: July 10, 2017, 05:42:20 AM »
The new supporting ring must be stiff but not too heavy and so I want a hollow composition.
« Last Edit: July 10, 2017, 06:40:22 AM by mbouwer »

mbouwer

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Re: Active Pitchcontrol
« Reply #776 on: July 11, 2017, 06:22:42 AM »
After welding I've got a ridgid inner ring.

mbouwer

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Re: Active Pitchcontrol
« Reply #777 on: July 14, 2017, 05:42:35 AM »
Supporting ring enhanced version.

mbouwer

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Re: Active Pitchcontrol
« Reply #778 on: July 15, 2017, 03:39:43 AM »
Now I have 2 supporting rings + lamination core. After drilling and bolting the small one
I want to remove the laminations and polish them.

mbouwer

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Re: Active Pitchcontrol
« Reply #779 on: July 16, 2017, 02:39:49 AM »
The burrs are polished and the laminations feature a layer of varnish.

hiker

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Re: Active Pitchcontrol
« Reply #780 on: July 16, 2017, 08:44:11 AM »
Looks great...with bigger coils..its possible to weaken your mags with to large of a load..or shorting out gen ...coils put out a reverse field under load and will weaken the mags if not sized for the coils.. My Pedgen has thin neo mags glued on top of ceramic mags..I've noticed overtime and abuse they have lost a bit of strength...ceramics are still the same...
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mbouwer

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Re: Active Pitchcontrol
« Reply #781 on: July 17, 2017, 02:38:25 AM »
The laminations bolted back on the supporting ring. Should I apply stainless bolts here?

hiker

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Re: Active Pitchcontrol
« Reply #782 on: July 17, 2017, 04:04:02 PM »
Looks like you used hot glue as well ? Stainless may be better..iron might cause a bit of cogging..but if their buried in the lams..Should work fine..what about the coils ? Glued down. ? Make sure the coil legs are good and covered...
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