Build Motor yourself

[Vendetta277]

Hi fellas ,

after some time I'm now into the idea to build a 3phase brushless motor myself.
I already have 2 bearings that can hold an 18mm shaft. , a wooden baseplate and some material in general
i also own an arduino uC and got quiet some knowledge about electrotechnical engineering.

BUT i need some help with the ESC and motor design.

base idea : 6 powermosfet for 3 phases is ok ..i think.
the motor should be around 1-5kW , and is allowed to be 30cm x 30cm x 30cm
im ordering some 50V , 40A N-ch. Powermosfets with 0.1ohms fully opened.
they are switched on and of by my arduino or arduino+driver circuit.
the uC is also the part that deals with my hallsensor placed near or between the coils in order to deliver positioning information.

i will need some big Capacitors ,too , but no idea how big they have to be in order to buffer those large values of current effectively.
theres obviously a big heatsink ,too

important questions :

1.Current
I want to have a maximum load current of about 80amps. so the current drawn when i start driving my cart will be around 150 amps or something
-> what size does my wires have to be in order to NOT burn down all the way ? ( am i allowed to use multiple wires for 1 coil so i reach a bearable division of current )

2. Design
there are neodymium magnets in all shapes and prices. and there are many designs to put together a bldc motor.
what would be the most effective way to put together coils and magnets ?
big outrunner magnets (4) and 12 coils ........OR............ 6 coils and 2 inrunner magnets.... OR ......... 9 coils on 12 outrunner magnets? ... OR even magnets each side to the coils (before and behind )
i still dont know what would be the most effective way to operate and build with.

3.Timing
as far as i know , those magnetic fields need time in order to establish and fall down , so the switching times are going to be earlier and earlier the faster the motor goes.
am i right ? or are those magnetic fields fast enough in order to up and down 100s of times a second.
--> most outrunner motors are wound arround ferrous material with a ferrous dome facing to the magnets.
if my thoughts are right , these are here to increase the density of the magnetic field lines , so the poles are becoming stronger. -> arent those slowing down the process of the pulsing fields ?


PLS HELP

I know , a lot of questions , but where would u find a REAL expert with REAL practical experience in building blcd's so easily.

greetz!

 

[amberwolf]

Your best "expert" is to read all the existing controller design/build threads, and the various motor design/build threads, too.

There's a LOT of details in those threads about how to do and figure out what you need. There's more than *I* understand, certainly.

 

[Vendetta277]

Hey Guys

I'm trying to build a DIY Motor myself , but it should have a max diameter of 8" and a max length of 15".
So it can really get a BIG motor. I want it to take 100V 100A full load , so 10kW input with an efficient design

I hope I am not bothering you with my questions but I am REALLY trying to get this going
I want it to become a 3Phase WYE wound Axial Flux Motor, maybe even several stators n , as your rotary discs with the magnets would be n+1 in quantity.

My questions are : neodymium Magnets ... better use discs or blocks , and how big makes sense ? should they be about as wide as your coils, smaller or greater?
coils : i want to use 9 or 12 coils per disc ... BUT round , or triangular..ish i dont know what would be the best design , and i dont know why people make so big center holes in their coils .
the coils should be as narrow as possible in the disc , as the magnetic field strength decreases the broader the coils get .. or not ?
100Amps continous battery current will result in which AWG size in order to not overheat wires? better many little wires or 1 big fat wire that takes all the current ?

it doesnt have to be perfectly efficient or anything , but i want it to have at least a nice design with reasonable sizes of magnets , coils and stuff

 

[Lebowski]

Hey Guys

I'm trying to build a DIY Motor myself , but it should have a max diameter of 8" and a max length of 15".
So it can really get a BIG motor. I want it to take 100V 100A full load , so 10kW input with an efficient design

I hope I am not bothering you with my questions but I am REALLY trying to get this going
I want it to become a 3Phase WYE wound Axial Flux Motor, maybe even several stators n , as your rotary discs with the magnets would be n+1 in quantity.

My questions are : neodymium Magnets ... better use discs or blocks , and how big makes sense ? should they be about as wide as your coils, smaller or greater?
coils : i want to use 9 or 12 coils per disc ... BUT round , or triangular..ish i dont know what would be the best design , and i dont know why people make so big center holes in their coils .
the coils should be as narrow as possible in the disc , as the magnetic field strength decreases the broader the coils get .. or not ?
100Amps continous battery current will result in which AWG size in order to not overheat wires? better many little wires or 1 big fat wire that takes all the current ?

it doesnt have to be perfectly efficient or anything , but i want it to have at least a nice design with reasonable sizes of magnets , coils and stuff

The triple stator AF motor I build and described here on this forum will fit your spec and will take 100V 100A, IF you can get it balanced enough to run at 4000 rpm.
At the moment I use it at 100V, 30A but limited to 1500rpm. Have a look at the thread... One thing I would definitely not do anymore is go for 9 coil, 12 is better there then
the torque is symmetrical w.r.t. the axle, with a 9 coil the torque is only on one side (making the motor noisy under heavy load)

 

[Vendetta277]

thank you , sir , i will look up your thread and be drilling with questions soon i think

 

[Miles]

BUT round , or triangular..ish i dont know what would be the best design , and i dont know why people make so big center holes in their coils ....the coils should be as narrow as possible in the disc , as the magnetic field strength decreases the broader the coils get .. or not ?

The object should be to get as much of the "coil" as possible running in the radial direction (in relation to the motor axis). When the wire is running in the circumferential direction, it doesn't contribute to the generation of torque....

 

[Vendetta277]

Thx Miles , now i get why they are designed that way.

Is there a good formation of magnetes other than 14magnets to 12 coils , such as 12 coils 9 mags ?
the magnet form should overlap the coil as much as possible , doesnt it

greetz

 

[Miles]

such as 12 coils 9 mags ?

You mean 10 magnets? The magnetic poles are always an even number. There are many possible combinations - each a compromise among different factors.

 

[Miles]

See: https://www.emetor.com/edit/windings/

 

[Vendetta277]

Yes , i meant 10 magnets as 9 wouldnt make any sense in order to have a nsnsnsns config

Well...the thing is about saving a bit of money.
N42 Neo's are superexpensiv as you are surpassing sizes of 25mm somewhat.
As expensive is a very relative term , i want to stay cheap , otherwise I could directly buy a Turnigy CA 80-100 or a motor alike , as the Turnigy is not built anymore.

One way i thought about is to buy much more of those little suckers ( 10-20mm ) and form them to an array or even field of magnets , being able to substitute 1 big neodymium magnet.

I saw a cool magnet which would perfectly fit an outrunner , maybe also a AF motor , radially placed.
Im talking about a Neodymium Magnet of the size 60mm x 20mm x 5mm , rated to pull 80kg or nearly 200lbs.
Those are 5€/each , and if I would go for 14 magnets per disc , we would land at 70€ x 2 for my rotor discs. really expensive

Greetz

 

[Vendetta277]

Hi guys !
How do I calculate my phase resistance , out of my given motor parameters that i want.
Or else - what phase resistance with which wire should I approximately aim for , to get along with 90V batteries and 100A continous current?

greetz

 

[Futterama]

Hi Vendetta277,

If you are building a motor because you want it to be cheap, I think you might get dissapointed. In my experience, it rarely gets cheaper by building stuff like this yourself. I would advise you to build this because you CAN, and because it is FUN. Of course you don't buy the most expensive stuff for your project, but you spend a lot of time finding the cheapest alternative for what you need, no wrong in doing that.

Regarding buying magnets, the only place I know of is http://www.supermagnete.de