Open source BLDC motor project

[Caspianlake]

Mechanical Engineering major here, I did a BLDC motor design in Simcenter Motorsolve, the simulated values were showing good results so I ordered the magnets and coils and will make the motor as soon as they arrive.


Here are the motor specs I designed the motor around:
Type: BLDC Inrunner Ironless
Voltage: 48V
Amperage: 24A
Rated speed: 5500 RPM
Rated shaft output power: 1 kW
Core Diameter: 130mm
Core height: 40mm
Magnet grade: N35
Slots/Poles: 18/16
Winding strand diameter: 1.3mm

I chose an ironless design for 2 reasons:
- Efficiency
- Ease of manufacturing with little equipment (you avoid silicon steel laminations, while not the hardest thing to source, its still more hassle than 3D printing the core out of PET-GF)

I am aware real life efficiency wont be as good, but I'd love to hear any feedback on it in general. Or if there is any glaring issues please let me know. As soon as I finish the motor design in CAD I will open source it.

[Caspianlake]

Looks like the CAD image didnt attach so.

[MariuszD]

If there is no metal in the motor, then why are there pole shoes there?
It looks like a design of a classic motor, using materials with high magnetic permeability.

[Caspianlake]

I left them in the design with the thought that they may help with the winding process

[Benta]

Does the rotor have slip rings?

[Caspianlake]

Does the rotor have slip rings?

Uh why would it? Its a brushless DC motor. It will have 608 bearings to lay on but no slip rings.

[Benta]

Does the rotor have slip rings?

Uh why would it? Its a brushless DC motor. It will have 608 bearings to lay on but no slip rings.

Sorry, missed the "N35 grade" point. Your CAD drawing suggested that the rotor would be wound as well. I suppose the magnets will be glued into the recesses.

[Caspianlake]

Yeah that is correct.

[Conrad Hoffman]

Really cool and I've pondered similar things. With 130 mm diameter, I'd be sure to raise the blast shields if you're going anywhere near 5k rpm. Maybe you can look at stresses in CAD.

[Caspianlake]

Really cool and I've pondered similar things. With 130 mm diameter, I'd be sure to raise the blast shields if you're going anywhere near 5k rpm. Maybe you can look at stresses in CAD.

Thanks! And definitely I will not be near it when I'm testing 5K and I wont test 5K right away. I did some rough calculations on centrifugal forces, so I have an idea of what to expect and indeed I may run an FEA before I ramp up to high speeds.

[Caspianlake]

Here is the github repo containing the STEP files as promised:
https://github.com/Caspianlake/LE-ElectricMotors

[Caspianlake]

I have changed the rotor design as the old one would have caused  a lot of trouble.

[MariuszD]

I wonder if the results from the simulation program shown above were obtained under the assumption that both the stator and rotor are made of a material with a relative magnetic permeability equal to 1.

Machines that do not have a core made of high permeability material usually have poor efficiency.

[Caspianlake]

I wonder if the results from the simulation program shown above were obtained under the assumption that both the stator and rotor are made of a material with a relative magnetic permeability equal to 1.

Machines that do not have a core made of high permeability material usually have poor efficiency.

Yes, they were made with a material with permeability equal to 1, in this case in simcenter motorsolve there is a specific "Non Magnetic" material for it.

[Berni]

A non magnetic rotor is likely not that big of a problem, the magnets themselves are high permeability material and you can compensate for the loss in field strength by using a larger magnet.

More of the problems are likely going to be from the stator not having a core. There is no magnetic material at all to collect the fields if it is just copper and plastic. To make things worse compensating for the field strength due to not being focused means running more current trough the coils (causes more heat losses) or having more turns (limited by physical space). Also the majority of heat is generated in the coils and plastic is not a good heat conductor to help move that heat away.

Ultimately the long term limitation for BLDC motors is usually heat. But given that this motor has no core to saturate it could be capable of some very high peak powers, but for very short periods of time.