Invented new type of DC motor? - Page 1
Forum section: electronics / beginners

author: petrex
author_rank: Newbie
timestamp: May 11, 2016, 08:40:00 pm
content: Hello eevblog user. This is my first post on this forum. The reason I am rising my question there is because I consider all of you as best on line electronics community i know. My younger brother have no clue about electronics at all and comes with idea of new type of electric motor. We build together functional prototype. We was not able to find such motor type anywhere. Today i gave myself some time to fill Instructableshttp://www.instructables.com/id/DC-Through-Coil-Motor/We do not know how to deal with it, so we just shared all details as open source hardware do. Please let me know if this already exists, have some name, is used in field for something and so on? I call it "DC Through Coil Motor" because rotor goes through coils. More info is on instructables linked above. Will be glad for all kind of thoughts.Video:Thanks, Petr.

author: jolshefsky
author_rank: Regular Contributor
timestamp: May 11, 2016, 09:21:28 pm
content: Weird. I wonder if it's got any characteristics that could be valuable ... I have a suspicion that efficiency and torque aren't very good, though.I see in the Instructable you considered making it part of a planetary gear system with the moving rotor as the ring gear. But I'm pretty certain that will act to increase the motor's output speed which is seldom what's desired. You could make the rotor the sun gear instead and the planet gears would necessarily be fixed (since they'd otherwise smack into the coils), and the output would be on the ring gear with a reduction ratio of (sun):(ring). This would make a hub motor like for directly driving a wheel.

author: petrex
author_rank: Newbie
timestamp: May 12, 2016, 06:00:09 pm
content: Great idea to make rotor as sun. So my plan for V3 is:Planetary gear, rotor as sun (gear ratio for more torque), planets and coils are fixed between each other to prevent collisionHerringbone Gears to be able to center rotor itself3 set of coils for smooth movement (coil pair are marked by colors in picture bellow)driven by ESC - I will measure hobby grade out runner and do same coil resistance for my prototype. I will be able to use hobby ESC then.What do you think about metal core for coils? Solenoids get more power when metal core is used. Question is how will work with neodymium magnets in rotor? I dismiss this idea for second prototype because I though it should be problem.I prepared some 3D how V3 will look like:What do you think?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 12, 2016, 09:50:35 pm
content: So, it's a reluctance motor? Meaning: the coil (no core, no pole pieces) pulls a permeable (iron) core towards it, then turns off as it passes through the center of the coil?If so, then the power density will be very poor, core heating (due to the changing magnetic field through the armature pieces) will be large, and torque ripple will be huge (indeed, just look at the poor thing shaking away in the video!).It gets better with permanent magnets, or solid copper armature pieces, and pole pieces around the coils, but it's still not much better than a conventional stepper motor (a hybrid reluctance and permanent magnet design, with way more steps per rotation than the number of poles suggests, good for precise angle control), or a conventional BLDC (typically 3 phase, permanent magnet) machine.Tim

author: petrex
author_rank: Newbie
timestamp: May 12, 2016, 10:39:04 pm
content: Tanks for response. Actually its not reluctance motor. It contains permanent magnets inside rotor. And next version will be 3 phase. So it will be the same as BLDC, with the difference of coil placement. Coils are not in our out of the rotor (in runner or outrunner) but around the rotor ( like inside runner:D ).

author: Mechatrommer
author_rank: Super Contributor
timestamp: May 12, 2016, 11:06:43 pm
content: con:1) hard to manufacture2) bearing wearpro:1) compact (given that the torque/power is acceptably efficient)i believe if this thing is a go, it will existed long time ago.. why reinvent the wheel?

author: CatalinaWOW
author_rank: Super Contributor
timestamp: May 13, 2016, 02:13:57 am
content: So it is not a new "type" of motor. It is an electrically commutated multi-pole motor. It is an unusual configuration. I see some pole pieces interior to the rotor. I believe that if you plot magnetic fields you will find that there are better arrangements for these pieces, and that the motor will benefit from exterior pole pieces also. You don't want to waste flux lines in the air, but instead concentrate them in the regions which are contributing to the work performed. Be sure to think 3D, not just looking into the face of the rotor. It is not obvious to me that this configuration has advantages in any application, but maybe. I would be very concerned about losses in the gear train required to support this. Also, any electric motor benefits from small gaps in the magnetic path. This gear supported rotor makes it difficult to achieve small gaps.

author: charlespax
author_rank: Regular Contributor
timestamp: May 13, 2016, 07:58:14 am
content: I'm sure they some use in a time machine. It looks pretty badass O0 Does it basically behave as a bunch of solenoids in a ring?

author: amyk
author_rank: Super Contributor
timestamp: May 13, 2016, 11:43:29 am
content: The term you're looking for is "torus motor" or "toroidal motor", and it has been reinvented many times (free energy/perpetual motion quackery included) and even patented:http://www.google.com/patents/US20060163970

author: max_torque
author_rank: Super Contributor
timestamp: May 13, 2016, 01:46:50 pm
content: It also has terrible iron / copper fill density for it's package envelope, so will never be that efficient......Far, far better to run with a conventional rotor arrangement, and put any epicyclic geartrain in the "dead" space in the middle (space which carries a low magnetic loading and hence isn't useful for making torque.Take a look at how the GM volt motor/gear train arrangement works for example:

author: ali6x944
author_rank: Frequent Contributor
timestamp: May 13, 2016, 03:17:42 pm
content: Amazing I realy like it !But consedering the fact that it is coils "dragging" the core it is going to shake like hell , so recommend to "suspend" the core in some way for example to make the gap between the core and the coils bigger so it doesn't drag against the coils the core could be suspended by ball barings , make sure that they are not stiff ... the core should be moving freely and please could u mount it , fixings it in place would be great!Also as u posted it is best to use the sun arrangementfor the gears but in all nice work man, it is nicely done, but could u post the driver circuit and method please I'm curious to know how that work...Hope the best for you and your project it is nice to see stuff done by innovative peaple