IanFiTheDwarf
10 W
Hi guys, I am pretty new on here but been lurking for a while. I’ve been designing an axial brushless motor which I’m hoping will be able to produce about 100kw. I have a few problems and a lot of questions which I will go into in a bit but here’s a description of what I’ve got so far,
I am planning on having 12 coils and 16 magnets as I want to use wedge shaped magnets (arc segments) and 16 seems to be the only number I can find of the shelf with the right angles to make a complete circle of suitable size.
I also want to use a halbach array but rather than trying to find wedge magnets which are magnetised in the right direction I’m just going to use rectangular magnets between the wedges. I tried this arrangement on FEMM and while it’s not perfect I think it’s a good compromise.
These are the magnets I’m planning on using.
http://www.magnet4less.com/product_info.php?cPath=1_15&products_id=457
http://www.magnet4less.com/product_info.php?cPath=1_15&products_id=501
I would prefer to use the 1/2” thick ones but that would need 2”x1/2”x1/2” bar magnets to make the halbach array and that makes the backing disc just slightly too big to fit in my lathe. The 1/4” thick magnets will probably be strong enough with the hallbach array anyway so I will just have to go for them and save some cash. I could use the larger magnets if I don’t have a lip on the outside edge of the backing disc but I am concerned about holding such large magnets with only glue at 4-5000 rpm.
For the coils I’m intending on casting my own powder cores, I’ve tried casting some resin parts before and even helped a pall make a toilet seat with a Nintendo Gameboy in it a few years ago so I think it’s possible. I will be using Magnetite since it’s cheap but there are alloys available with higher permeability. The coils will be for a fairly low voltage for this sort of power range. From my calculations going this way will reduce losses but it will also make the control more difficult.
I also think keeping the voltage down has other advantages. Safety, simplified battery charger and BMS.
For the motor controller I had originally thought about building the power stage and commutation logic into the motor so that it would only need a battery supply and a pulse width modulated throttle signal to run, but after reading Lebowski’s threads on his controller I could never get that level of control and functionality with a simple on-board controller. I may be pestering him for one of his Controller ic’s.
Please comment freely.
Cheers
Ian
I am planning on having 12 coils and 16 magnets as I want to use wedge shaped magnets (arc segments) and 16 seems to be the only number I can find of the shelf with the right angles to make a complete circle of suitable size.
I also want to use a halbach array but rather than trying to find wedge magnets which are magnetised in the right direction I’m just going to use rectangular magnets between the wedges. I tried this arrangement on FEMM and while it’s not perfect I think it’s a good compromise.
These are the magnets I’m planning on using.
http://www.magnet4less.com/product_info.php?cPath=1_15&products_id=457
http://www.magnet4less.com/product_info.php?cPath=1_15&products_id=501
I would prefer to use the 1/2” thick ones but that would need 2”x1/2”x1/2” bar magnets to make the halbach array and that makes the backing disc just slightly too big to fit in my lathe. The 1/4” thick magnets will probably be strong enough with the hallbach array anyway so I will just have to go for them and save some cash. I could use the larger magnets if I don’t have a lip on the outside edge of the backing disc but I am concerned about holding such large magnets with only glue at 4-5000 rpm.
For the coils I’m intending on casting my own powder cores, I’ve tried casting some resin parts before and even helped a pall make a toilet seat with a Nintendo Gameboy in it a few years ago so I think it’s possible. I will be using Magnetite since it’s cheap but there are alloys available with higher permeability. The coils will be for a fairly low voltage for this sort of power range. From my calculations going this way will reduce losses but it will also make the control more difficult.
I also think keeping the voltage down has other advantages. Safety, simplified battery charger and BMS.
For the motor controller I had originally thought about building the power stage and commutation logic into the motor so that it would only need a battery supply and a pulse width modulated throttle signal to run, but after reading Lebowski’s threads on his controller I could never get that level of control and functionality with a simple on-board controller. I may be pestering him for one of his Controller ic’s.
Please comment freely.
Cheers
Ian
