Adding hall sensors to outrunners

[olaf-lampe]

Rewinding is no issue, the wires aren't epoxied yet. But before I do that, I check the last unwound stator for lamination shorts with each other or with the shaftholder. If that's the cause for the trouble, Markobetti will get a package from me...

I gathered all my guts and tested the turnigy with the all new 150v 12FET infineon I got from Lyen. And it runs smooth as butter at 120V
The scope picture didn't look much different to the previous one: The spikes are not the problem though.

t80-85_100t_w120V.jpg (141.24 KiB) Viewed 855 times

t80-85_120V.jpg

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Have a nice sunday
Olaf

[Jeremy Harris]

I don't think that inter-lamination shorts or a short from the laminations to the bearing carrier would have this big effect, although a winding to lamination short might. My money is still on a shorted, or partially shorted turn somewhere, or maybe a turn shorted to one of the laminations.

Jeremy

[olaf-lampe]

When I mount the bell on an empty stator, would it run free if the stator has shorts with the shaftholder?

It's ironic, I had to remove the original wire from the turnigy and hadn't been extra careful using a lathe to cut off the copperhead and a hammer to punch out the epoxied wires.
Turns out, this is the only motor running well so far.
BTW: It runs without skirt bearing so far. That's where the 0.1A noload current comes from.
-Olaf

[Jeremy Harris]

When I mount the bell on an empty stator, would it run free if the stator has shorts with the shaftholder?

I think it should, as any eddy currents are going to be mainly flowing in the outer edges of the stator - I don't think that having the stator laminations contacting the shaftholder would cause a problem.

BTW: It runs without skirt bearing so far. That's where the 0.1A noload current comes from.

That doesn't surprise me, for the sort of use we're putting these motors to I don't think we really need the skirt bearing. Exceptions would be people making friction drives and maybe someone building a trials or dirt bike, where severe shock and vibration might present a problem, but most of the time we're not loading these motors with anything like the side and gyroscopic forces that an aerobatic model aircraft would impose.

Jeremy

[Ludo91]

Guys Im lost! what should be the hall sensors spacing on a turninigy htx 80-100 (12 pole 14 magnets) ?! tnks!

[marcexec]

Can someone put this very simpy:
Where and in which direction do I put the (3) hall sensors inside an Outrunner, on the stator?
I read through all this and are not much wiser.

[Burtie]

There is a lot of explanation in this thread:

viewtopic.php?f=30&t=9061&p=325809&hilit=+4th+slot#p325809

[marcexec]

Thanks, Burtie!
It's easy to get lost sometimes...

[modern_messiah]

OK I've read through this thread a few times (and even replied a while back) but it's getting so long that I found myself skim reading, missing parts and getting annoyed with myself so I'll just ask for a quick clarification to the following:

As previously stated I have an Axial flux motor that I am building. I want to mount hall sensors internally on the stator. It's a 9 tooth, 6 pole motor. This means the motor has 3 pole pairs. 360/3 is 120 degrees, with 3 hall sensors that means they need to be placed 40 physical degrees apart from each other around the stator.

The question is thus: is there a specific place they should be placed? Right in the middle of a tooth/coil? In the gap between teeth? Towards the outer rim of the stator or (as I suspect) as close to the center of the magnetic pole pairs axis as possible? I understand the position is calculated relative to the position of the stator - but how does the controller know where on the stator the sensors are located?

I'm going to go back and read some more I think...

EDIT: I have read through the thread Burtie linked to above, but as with this one I probably managed to miss the important bits. For the record I get the impression that sticking them between the teeth (the spaces between each adjacent coil) at around the distance from the center of the axis of rotation to half way up the coils is the way to go.

[olaf-lampe]

You'll wind the stator ABCABC... which makes it neccessary to put the halls right in the middle of a tooth. If you put it between teeth, you'll need to know which direction the motor will spin. One direction you'll have a retarded hall signal; in the other it is advanced. The best way of course is to make it adjustable...
-Olaf

[modern_messiah]

You'll wind the stator ABCABC... which makes it neccessary to put the halls right in the middle of a tooth.

How do you know this? Where is this written? Probably in one of the threads I've read through a million times. *sigh* If you have the time can you explain why this is the case for ABCABC? How is it different to any other winding scheme?

I'm not questioning your response - I'm simply trying to understand why this is the case so I learn something instead of just blindly doing something some one tells me is correct. Basically so I understand the principles and don't have to ask again in the future!

I think it's called learning

[olaf-lampe]

With an AabBCc winding like the usual turnigys have, you can put the halls between the Aa/bB/Cc coils. That's a timing-neutral place and works for both directions. With an ABC winding, the only neutral place is the center of the coil.
-Olaf

[modern_messiah]

Bugger. Putting them dead center of the coils will be a pain. Oh well, another puzzle to solve

[spinningmagnets]

As someone pointed out to me a while back, a hub-motor is an outrunner with the spokes attached to the shell. On the new Crystalyte hubs (HT/HS) the first batch didn't have hall-sensors, but they all had the factory-cut slots for them:
http://endless-sphere.com/forums/viewtopic.php?f=2&t=24593&start=165#p381693


And in the Tucson "Death Race", PaulD's winning Turnigy 80-100 had external halls spaced at 17.1 degrees
http://endless-sphere.com/forums/viewtopic.php?f=3&t=24507&start=330#p390931

[modern_messiah]

Well %$^&.

Using 9 teeth and 12 poles (ABCABCABC) requires the magnets to be placed 20 physical degrees apart from each other. However it is not possible to place them all in the center of a tooth. In fact one will be centered, while the other 2 will be right between the teeth either side of it.

How can this be fixed, if at all? Or is this something that can be fixed by adjusting them a few degrees (i.e. keeping them at 20 degrees to each other but rotating all 3 a few degrees relative to the teeth)?

[TylerDurden]

@ m_m:

Is there a problem physically placing the sensors at the perimeter of your stator?

If so, you can also consider optical sensors. IIRC, Tidalforce motors did .

[modern_messiah]

Is there a problem physically placing the sensors at the perimeter of your stator?

I'm not totally sure what you mean by this? I can place them anywhere I want - internally, externally on a separate jig (behind the backing plate so it will rely on flux leakage) and so on. What I mean is that Olaf stated the best place was the center of the coils as this is 'timing neutral'. However if they are placed at 20 degrees, as required by my motor you get the following:

Looking perpendicular to the rotation of axis - this is an axial flux motor. Blue circles are coils, black dots are hall sensors, the grey is part of the stator holding the coils in place.


Notice the 2 outer sensors are unable to sit directly in the middle of a coil like the center sensor can. No matter how I rearrange the sensors, if I want to keep the 20 degree separation between sensors this will always be the case. Is this a big problem Looking at the picture of the Crystalyte hub above it has a similar problem, though as Olaf hinted to earlier this apparently has something to do with the winding scheme?

I'm so lost lol.

[olaf-lampe]

I don't see a reason, why you couldn't put them 120° apart... anyone?
Just make sure they see the whole diameter of the magnets, otherwise you waste precious dutycycle.
-Olaf

[modern_messiah]

I don't see a reason, why you couldn't put them 120° apart... anyone?
Just make sure they see the whole diameter of the magnets, otherwise you waste precious dutycycle.
-Olaf

1) Can you explain the 120° theory? I'll give it a go now actually...I pieced this together from various sources so I won't be surprised if it's very wrong.

To place Hall sensors properly in a motor, you have to know how many electrical degrees each tooth occupies:

°elec = 360 * p / t where p = number of pole pairs & t = stator slot count. For my motor °elec = 360 * 6 / 9 = 240°

The first sensor is placed anywhere - this becomes zero degrees. I will place mine dead center of a tooth as this is "timing neutral". The second sensor must be °elec ahead of the first sensor. Each tooth is 240 electrical degrees. Begin at the position of sensor A as this is 0°. Add the °elec to each previous position until you reach 120° (this is the desired location of the sensor). Obviously each time you pass 360° you subtract it.

So you end up with:

1) 0 + 240 = 240.

2) 240 + 240 = 480. Subtract 360 = 120. The number of iterations is 2 and seen as you are at 120° the second sensor should be placed 2 slots away from the first.

You now treat the second sensor as the starting point in order to place the 3rd sensor 120 elec° from it. You get the same result for sensor 3. So according to my maths my sensor placement should look like this:



If I was to do as you have suggested Olaf, there would be 2 empty teeth between each sensor.

Can someone clarify this? What's right!?!?!

[olaf-lampe]

Maybe both theories are right.
For the hall sensor it doesn't matter which magnet triggers. As long as the magnet has the right polarity and the right timing. I'm pretty sure, there is a propper magnet in 20°, 120° and 240° distance from the first hall.
You should paint the magnets in your picture red or blue ( north/south) to clearify that.
-Olaf

[modern_messiah]

The blue rings in the above drawings are coils...let's try again.

Black dots are Hall sensors, Yellow Circles are Coils, Blue and Red are magnets (alternating of course).

[olaf-lampe]

I stand corrected. That picture clearly shows, the 120° doesn't work here.
The way you've drawn the hall's is the way to go.
-Olaf

[modern_messiah]

I stand corrected. That picture clearly shows, the 120° doesn't work here.
The way you've drawn the hall's is the way to go.
-Olaf

Wait...I got something right? I'm learning!!!

Progress feels fantastic

EDIT: Just for clarification; is the reason 120 physical degrees won't work because if you put them at this separation all 3 hall sensors would be over magnets of the same polarity at the same time, and hence the controller would have no idea which way it was going?

[Thud]

in the above illistration the halls are not 120deg apart. they are near 90 deg. 120 will work on any 3-phase machine.

now to the report:
I have gone to internal Hall sensors on a re-wound Turingy 80-100 motor & can say that the 12fet controller is finaly delivering enough performance to keep me interested.

Thanks for the steerage Burtie. I doubt I will ever recomend external placement again....wich sucks as I built tooling to make a Jiffy slip-on Hall bracket for the turnigy motors with the halls cast in resin & idiot proof for instalation & set up....now thats out the window...I am goig to go make a video & kill a few battery packs!

[HumboldtRc]

I'm still trying to figure out which slot to start the placement of the sensors....?
Do I just chose any slot and do the 120 degree spacing??