Magnet dimensions
 

Boys, I was thinking about the dimensions of our magnets, and then it hit me: The Lehner numbers must be the diameter and lenght of the magnet!
For example: 1940 - 19mm diameter, 40mm lenght.

Sounds reasonable, doesen't it?

I know for a fact that the Feigao (or Wanderer) L-motors have 19x30mm magnets. So the XL will have a 50mm long magnet? Just guessing.

I thought I should share this interesting train of thought, but maybe you guys knew about this.

DAF

So following that theory a 2240 would be 22x40. Sounds plausible.

Exactly. Which equals to 15,2 cubic cm of magnet for the 2240, and 14,18 cubic cm for a 1950. (hole for shaft neglected)

Re: Magnet dimensions
 

I've often wondered what a good example would be to demonstrate the differences between the really technical folks and us not-so-technical folks. The fact that you start your post with "I was thinking about the dimensions of our magnets..." is exactly the example I have been looking for :)
This is why you guys recommend systems and I just race them :)

7XL = ? :D

Yeh it makes sense with the number model, I guess the 7XL goes by another number?

7 is for the number of winds or turns isnt it?

Feigao 540 Rotor Lengths:

S: 21 mm
L: 30 mm
XL: 45 mm

I think they're all 19 mm in diameter.

A lehner 1950 is the same length as a feigao XL though(externally),so on that basis wouldn't it be a lehner 1945?Maybe it does have a 5mm longer rotor though.Anyone feel like opening up their 1950 to find out?

Coool thinking Daniel!!!!

really cool!!

Re: Re: Magnet dimensions
 

LOL yeah, scientist at heart. Always wonderin' about the How and Why, and how to improve things. Can't be helped, and can't be stopped either, the brain just rattles on and on.

Maybe I should tell you why I was thinking about that. Well, those Lehner guys sell their nice magnets as spare parts....the rest of the story is obvious.

Cheers
DAF

Not that obvious to me.You were going to try a 1930 rotor in a 9L or something?Could be a cunning plan maybe.

That's another reason why those Lehners have better efficiency: Longer magnets in comparison to the copper strand layer. The copper "behind" the magnet does nothing for power, it's just electric loss.
I'm almost sure the 1950 has a 50mm magnet, and the Feigao XL have 45mm.


Yeah, exactly. The Lehner magnets alone are rather cheap. And the 1950 already has a 5mm shaft, too.

perhaps i should get a 1950 too.. Instead of an 11xl... Come to think of it..

Sounds like a very cunning plan then!How much is a replacement magnet?

So ageing 'L' motors could become a poormans 1930s and 'XL' become 1950s.Marvellous!

I don't think making a lehner out of a feigao is going to be that easy as to just change the rotor(armature). The copper strands help make up the magnetic field to push the magnetized rotor. So I kind of disagree on they are just electircal lose.

Worth an experiment though.It wouldn't make it a Lehner no,but if it fits then the segmented magnets might be an improvement.Only one way to find out i suppose.

Maybe the copper strand behind the magnet isn't all loss but presumably less efficient than that around the magnet(i don't really know).It all adds up.

I took a lehner 1930 10t apart. I also had a feigao 8l I took apart. here is some difference. The windings in a lehner are a lot closer than the feigaos are.

Very interesting indeed.What's that on the ends of the 8l magnet?
Do you think the lehner rotor could fit with some spacers made?
Rear bearing inner diameter looks different too.

the lehner 1930 has 4mm shafts. They are like rings on the end. I don't know if it would be enough gain to talk about or any at all.

Of course. I just meant the part of copper strands that are not at the magnet. The part where all the winds are knitted together, on the rear of the motor.

Nice pic, Leeroy. Thank you. I'm kinda dissapointed that those segments are this fat! Somebody told me the segmenting would be most efficient if the segments are 0.2mm thick. (almost zero eddy currents)

Wasn't that me Daniel?

that is the same experience i have with transformers.

I saw that pic, and thought the same thing, about the thickness of those layers.

Possibly, Rene. Let's see what the BK boys bring on.
At least Lehners 2.5mm segments are better than the big Feigoa blocks.

Also, the outer Can, the actual motor housing, is fine layered. And I noticed the Lehners seem to have thinner layers than the feigaos. (just for clarity, I'm speaking of the stuff that's purple on Feigaos and black on Lehners.... the motor housing is kinda like a stack of rings, if you know what I mean)

I saw a pic of a plettenberg rotor and it had much thinner segments than the lehner.

Here's another one: On the HiAmp versions of the Lehners the windings are visible. The wires ar the back are the actual windings, just like with Feigaos. Now, the higher turns have much thinner windings (the bundle is thinnner) than the lower turns. Why is that?? And has this an influence to the torque?

Thank you
DAF

Reason for that is because they need to route longer wire in the higher winds than in the lower winds Daniel, it simple is thinner and longer. Get it?

A higher KV has got a higher resistance because of this.

Thank you rene, we might talk about this some more later on.

Here's some news I learned in regard to those segments: Altough thinner segments would gain efficiency, they would rob torque. So the Lehner design must be some kind of ballance then.

Just thought I should share this with you.

I think you referring to different type of motor...
The only advantage of making rotor from sections is to get stronger magnetic field (in comparison with single one) and make it more uniform in production and probably uniformity of the magnetic field as well. To obtain higher torque you need to create more poles or add core but by doing that you sacrifice speed in first case and efficiency in the second one. Different wiring schemes are focused on reducing motor inductance and resistance, as well as heat dissipation (air is bad heat conductor, so special epoxies and winding pressing helps).
Also you can destroy magnets by applying high currents (especially when it is cold... well, different story) but in this case segmented magnet will be more tolerant to that situation.

Slots are great for stepper motors not for servo...

Artur

The kontronik motors uses big ( very big, actually.) segments in their rotors. There's only three segments in the rotor shown at their website, but probably its because the rotor is actually a 380-400 size. Probably the larger ones uses more segments, but I have to open up my FUN500-27 can and see for myself with eyes unclouded. The rotor is also nickle plated and it seems that the 19 series' rotor is also nickle plated to resist rust and humid. If the 500-27 rotor has only three segments, then I'll give up on the kontroniks and go for a 1940 instead, but then again, I'll pay 150 dollars extra for the 1940.

@griffinru;

The reason why to use segmente magnets, is because the eddy currents are much smaller, especially under partitial load. A segmented magnet hasn't neccesary got a higher magnetic strength than a non segmented.

not entirely; the power/diameter of the magnet is very relevant with this. And it is not said that a segmented magnet is stronger either. A big lehner motor (like the 2240/2250) will have loads of torque and at the right voltage it's also very efficient.

a 2 pole isn't weaker in torque than a 4 pole. (comparing a feigao XL with a plettenberg bigmaxximum)

A neodym magnet will loose his power above a certain temperature. (Daniel knows the exact number, i don't)

All the producers of BL motors use the pressed winding.

A 4 pole will definately have more kt than a 2 pole of the same wind. That's why the plettenberg shadow is a 1 turn.

Well, I thought maybe that would be easy to explain by making it too simple. And when I was talking about magnet power, I was assuming that with segments you can easy pick up similar power magnets to achieve consistent magnetic field across wide selection. But that maybe not true, I haven’t measured magnetic field individually myself and haven’t compared one either.
When I was talking about magnet losing its power, I was thinking about high currents not high temperature. Magnet can be demagnetized with high current, especially when it is cool. While demagnetization with high temperature happens at relatively high temp, so before you reach one something will be smoking pretty well. But on other hand everything possible.

Usually, Eddy current losses in the magnets are ignored, due to the fact that magnet magnetic field and windings magnetic fields are synchronized. However completely cannot be ignored because of braking, accelerating and timing.

There are couple ways to reduce or eliminate Eddy current losses different motor manufactures use different approaches, based on their R&D data. It is known fact that Eddy current losses dependent on the magnetic thickness, air gap, magnet width etc. Eddy-current loss in the rotor can be reduced by either increasing the magnet thickness and air gap length simultaneously, or using segmented magnets for each pole. The increase in magnet thickness and air gap length effectively reduces the effect of armature reaction, while segmenting the magnets reduces the Eddy-current loop areas. Using a shielding cylinder around the magnets (aveox BL motors), segmenting and side-insulating the magnets are popular solutions as well.

Torque – more poles, big diameter, longer can, bigger magnets, smaller air gap
Speed – less poles, small diameter, shorter can, relaxed air gap

And building motor with small diameter but very long can not a good idea because of shaft flex.

Artur

I never heard about a neodym magnet loosing its magnetical strength caused by a too high current. It is know from loudspeakers that the relative poor quality grey magnets can loose some of their magnetic force by dropping them or just loosing strength during the years. Neodym is nothing like that from what i have read. Could you please share your source for the information you have got on these magnets?

Ja, please share the source. I read many scientific puplications on magnets / rare earth magnets / motors or generators over the last few months, and this kind of information somehow got past me. Please share the knowledge.

Yes, please.

Probably you might find this site informative to some extent:
www.neodymiummagnets.info/neodymium-magnet.php

I was more interested in the source for the wisdom of griffinru..

Wisdom....wisdom?!!....may God grant us wisdom.

Since you have wisdom as well, Serum, may I ask you this question: is a rotor of thinner segments better than one with thicker segments? Daf said that the more thinner are the segments the higher is the effeciency and the weaker is the torque ( correct me please, if I misunderstood) and vise versa.
The kontroniks, the pletts and the lehners, by far ,are the only companies that uses segmented magnets, probably there are other companies I dont know about, but that is fine with me. Why I'm asking this question is because I need to decide whether I am supposed to go with the FUN600-13 with its low price or go for a 1950/10 motor and pay extra 200 dollars( though I know that the 1950 will take down the fun600-13 easily.) I'll be using one of these motors in my future heavy maxx. The fun600-13 is like a L wanderer motor with segmented rotor and the 1950...well, you know it better than I do. Please, answer it this time if you could not answer my PM.

It really isn't about the thickness of the layers in the segmented magnets, it is about efficiency of the motor.

From the experience of all the lehner 19/20 series users on this forum you can tell that the lehners are cool motors, also cool on partitial load, so based on that experience, you can jump to the conclusion that the lehners did a good job on the thickness of the slices.

I have got 0 experience with the kontronics, but my guess is, that they will be great as well. (better than the feigaos because of the segmented magnets) i would not be suprised if they would be simular in performance than the lehners.

I did not meant hisd wisdom in general, i meant his specific wisdom, regardig some stated 'facts' over the neodym magnets.

And i don't see why you need to push your question you did sent me with the PM. really no need for that.

I wasn't focusing on neodym magnets in particular but to create a magnet you need apply current, so to destroy you can do the same. If you look on different magnetic material specs it would be clear that neodym magnets require higher current, but still current (current ratings depend on magnet size). And with stronger magnets what we do? We make motors smaller.
Some of my posts based on information obtain from different sources (some of them might be not available anymore :( ) and some of them from personal experience. Google search brought me this link http://www.cy-magnetics.com/hauptseite.htm some of the information and specs can be helpful.

Artur

:) My appologies, modorator.