Thecoco974
10 W
- Joined
- Dec 7, 2016
- Messages
- 94
Hello everyone,
I've been learning a lot on this forum that is, as his name suggess, an endless source of knowledge on electrical vehical. I've stayed mostly on the Electric techhnology Discussion part of the forum and have been inspired by awesome threads like Lebosky's and APL's on motor building and by good general motor and controleur design discussions (most recently with HalbachHero's thread on his toroïdal axial flux design) .
I think I should share my build/design even though it might not work as intended.
After building a motor from hoverboard hubmotors and being disappointed by the high losses linked to too thick laminations i've looked for other motor desigh that looked somewhat DIY'able and could help me with my goal of reliable 5kw continuous power (and cheap to build, but i've come to realise that with prototyping it doesn't work at all).
Like other i've come to realise that the easiest way to diy a motor was to skip the steel core part and ended up designing an axial flux coreless permanent magnet motor.
A good inspiration for me (has you will see) was Ben katz pancake motor that is very well documented here : https://build-its-inprogress.blogspot.com/2015/02/coreless-axial-flux-motors.html
As stated above my goals with this design are the folowings :
- Continuous power of at least 5Kw
- Peak power of close to 10Kw would be fun
- Running voltage <60V (so 13S li-ion in my case)
- Scalability
- cheap materials
- Doable with small machine tool (a mini lathe bought for the occasion)
I haven't talk about the use case, for hub motor and mid-drive afficionados it might sound wierd, but the first vehical to receive this motor( if it fulfill the requirements) would be a front-wheel friction drive racing two wheeler. We have races where I live with those kind of stuff named solex that are quite fun.
Without further do here is the simplified design process i've followed until where I am now :
I've firstly looked for the widely available magnet dimensions (going for the cheap ones) and ended up buying 100 of the 40 x 20 x 5mm N37 neodymium magnet.
Starting with those magnets I then started doing a lot off FEMM simulations to find the optimal airgap based on the FOM procedure explain very well on this video : https://www.youtube.com/watch?v=AWJYCzGvYzs
The result ended up being somewhere around 9-11 mm airgap with twin 5mm back-iron rotor.
Being limited to a turning diameter of 205mm with my newly bought 8x16 lathe I ended up with a rotor diameter of 177mm and 7 poles pairs for an inrunner design and an outer shell diameter of 195mm. Here is how it look :
The stator as been inspired by ben katz design but without spreading each turn over the full phase pole occupation and keeping turn section going radially (copper section is a funtion of inner radius, number of poles and stator thickness). With a goal of increasing airgap copper density I have designed a 3D printed winding core that permit paper thin central membrane and after a lot of though gave me on option for watercooling (when going for inrunner type), here is my idea :
The skewing of the winding althought hurting the motor constant by decreasing flux linkage/angling the Laplace force vector/spreading current over an entire pole (pick the one you dislike the less) decrease the winding resistance enough to give an overall beter performing winding as found by Ben Katz (looking forward to do the calculus and find the same result). And the bonus being giving a way to watercool that thing, each pocket overlap two on the other side giving a circulating pass around the stator like this :
The pass might be to much restrictive but multiple inlet/outlet is posible if the flow is too low.
Being a flat design, stacking is good option for multiplying power capabilities here is my first design with 3 stator and 4 rotors :
(spacing messed up because of later part revision for another assembly)
This particular design, with single magnet thin inner stator, after motor constant calculation proved itself to be not much better than a two stator design with two magnet thick middle stator. This is mostly due to too low magnetic flux through the middle stator. Here the axial flux density through one pole with previous presented design and after the one with the double magnet center rotor :
The later version will be chosen because the first stator prooved itself to be time consumming to manufacture to say the least :lol:
A prototype is beeing build and I will share with you the state of it and the building technique used in a later post. It's coming quite slowly because of a lot of reasons (covid induced shortage on material/time lacking/me just being lazy/being a beginner machinist )
(by the way sorry for my bad english, beeing too lazy to correct it here ...)
I've been learning a lot on this forum that is, as his name suggess, an endless source of knowledge on electrical vehical. I've stayed mostly on the Electric techhnology Discussion part of the forum and have been inspired by awesome threads like Lebosky's and APL's on motor building and by good general motor and controleur design discussions (most recently with HalbachHero's thread on his toroïdal axial flux design) .
I think I should share my build/design even though it might not work as intended.
After building a motor from hoverboard hubmotors and being disappointed by the high losses linked to too thick laminations i've looked for other motor desigh that looked somewhat DIY'able and could help me with my goal of reliable 5kw continuous power (and cheap to build, but i've come to realise that with prototyping it doesn't work at all).
Like other i've come to realise that the easiest way to diy a motor was to skip the steel core part and ended up designing an axial flux coreless permanent magnet motor.
A good inspiration for me (has you will see) was Ben katz pancake motor that is very well documented here : https://build-its-inprogress.blogspot.com/2015/02/coreless-axial-flux-motors.html
As stated above my goals with this design are the folowings :
- Continuous power of at least 5Kw
- Peak power of close to 10Kw would be fun
- Running voltage <60V (so 13S li-ion in my case)
- Scalability
- cheap materials
- Doable with small machine tool (a mini lathe bought for the occasion)
I haven't talk about the use case, for hub motor and mid-drive afficionados it might sound wierd, but the first vehical to receive this motor( if it fulfill the requirements) would be a front-wheel friction drive racing two wheeler. We have races where I live with those kind of stuff named solex that are quite fun.
Without further do here is the simplified design process i've followed until where I am now :
I've firstly looked for the widely available magnet dimensions (going for the cheap ones) and ended up buying 100 of the 40 x 20 x 5mm N37 neodymium magnet.
Starting with those magnets I then started doing a lot off FEMM simulations to find the optimal airgap based on the FOM procedure explain very well on this video : https://www.youtube.com/watch?v=AWJYCzGvYzs
The result ended up being somewhere around 9-11 mm airgap with twin 5mm back-iron rotor.
Being limited to a turning diameter of 205mm with my newly bought 8x16 lathe I ended up with a rotor diameter of 177mm and 7 poles pairs for an inrunner design and an outer shell diameter of 195mm. Here is how it look :
The stator as been inspired by ben katz design but without spreading each turn over the full phase pole occupation and keeping turn section going radially (copper section is a funtion of inner radius, number of poles and stator thickness). With a goal of increasing airgap copper density I have designed a 3D printed winding core that permit paper thin central membrane and after a lot of though gave me on option for watercooling (when going for inrunner type), here is my idea :
The skewing of the winding althought hurting the motor constant by decreasing flux linkage/angling the Laplace force vector/spreading current over an entire pole (pick the one you dislike the less) decrease the winding resistance enough to give an overall beter performing winding as found by Ben Katz (looking forward to do the calculus and find the same result). And the bonus being giving a way to watercool that thing, each pocket overlap two on the other side giving a circulating pass around the stator like this :
The pass might be to much restrictive but multiple inlet/outlet is posible if the flow is too low.
Being a flat design, stacking is good option for multiplying power capabilities here is my first design with 3 stator and 4 rotors :
(spacing messed up because of later part revision for another assembly)
This particular design, with single magnet thin inner stator, after motor constant calculation proved itself to be not much better than a two stator design with two magnet thick middle stator. This is mostly due to too low magnetic flux through the middle stator. Here the axial flux density through one pole with previous presented design and after the one with the double magnet center rotor :
The later version will be chosen because the first stator prooved itself to be time consumming to manufacture to say the least :lol:
A prototype is beeing build and I will share with you the state of it and the building technique used in a later post. It's coming quite slowly because of a lot of reasons (covid induced shortage on material/time lacking/me just being lazy/being a beginner machinist )
(by the way sorry for my bad english, beeing too lazy to correct it here ...)