Search found 841 matches

by rhitee05
Mar 13 2012 8:55pm
Forum: Motor Technology
Topic: Dual rotor axial flux motor design
Replies: 458
Views: 40070

Re: Dual rotor axial flux motor design

The two-rotor design has good and bad aspects for the bearings. The good is that the magnetic forces will nominally cancel each other out as far as the bearings are concerned - the internal braces between rotors will take care of those loads and there will be net zero force on the entire assembly. T...
by rhitee05
Mar 13 2012 1:48pm
Forum: Motor Technology
Topic: Dual rotor axial flux motor design
Replies: 458
Views: 40070

Re: Dual rotor axial flux motor design

Do you think the reduced cross section (approx 1/3rd for <1 mm), where the two coils are connected in the middle, will cause any problems? I seriously doubt it. We won't be coming anywhere near the level of current where that would act like a fusible link, and it's such a short segment that the inc...
by rhitee05
Mar 13 2012 10:42am
Forum: Motor Technology
Topic: Dual rotor axial flux motor design
Replies: 458
Views: 40070

Re: Dual rotor axial flux motor design

Hey Miles, just wanted to poke my head in so you didn't think I disappeared. Had a busy couple of weeks, so I'm just getting caught up. I have the data from all the runs I set up for while I was gone partially processed, and there don't really seem to be any surprises. More iron, more magnet -> more...
by rhitee05
Mar 01 2012 8:44pm
Forum: Motor Technology
Topic: Dual rotor axial flux motor design
Replies: 458
Views: 40070

Re: Dual rotor axial flux motor design

Miles wrote:Anyone an IEEE subscriber?
http://ieeexplore.ieee.org/Xplore/login ... ision=-203
Yes. That paper and it's references look like interesting reading.
by rhitee05
Feb 29 2012 9:32pm
Forum: Motor Technology
Topic: Dual rotor axial flux motor design
Replies: 458
Views: 40070

Re: Dual rotor axial flux motor design

I'm headed out of town for a few days, so posting will be sporadic or nonexistent until Monday. However, before leaving I set up my computer to run a series of model permutations across what seems to be the most promising range of parameters. I'm checking 4/5/6 mm core widths, 2, 2.5, and 3 mm magne...
by rhitee05
Feb 29 2012 2:06pm
Forum: Motor Technology
Topic: Dual rotor axial flux motor design
Replies: 458
Views: 40070

Re: Dual rotor axial flux motor design

I'm not familiar enough with the Agni motors to speculate. It's possible they do have enough iron to avoid saturating.
by rhitee05
Feb 29 2012 10:59am
Forum: Battery Technology
Topic: Envia Systems twice the energy density of lithium cobalt
Replies: 63
Views: 5466

New Li Battery Tech Coming?

This is still a little bit in vaporware territory, but could be very promising if their claims hold true: http://spectrum.ieee.org/energywise/green-tech/advanced-cars/will-envia-be-the-envy-of-lithiumion-car-battery-makers http://www.wired.com/autopia/2012/02/new-lithium-ion-batteries-promise-lower-...
by rhitee05
Feb 29 2012 10:17am
Forum: Motor Technology
Topic: Dual rotor axial flux motor design
Replies: 458
Views: 40070

Re: Dual rotor axial flux motor design

Regarding the recent torque constant vs phase current plots (model5d), I keep wondering 'if the torque constant is higher at lower phase currents', why are motors not designed so they have a multiple of 3-phase groups so that each 3-phase coil set is operating in the max range of 15-20 amps? Certai...
by rhitee05
Feb 28 2012 10:56am
Forum: Motor Technology
Topic: Dual rotor axial flux motor design
Replies: 458
Views: 40070

Re: Dual rotor axial flux motor design

Overnight results - 6mm wide x 28mm long cores, 2x3t coils, stainless (air) pins, 0.75mm airgap, N48 magnets of varying thickness. Model5a Torque vs Current.png Model5b Torque vs Current.png Model5c Torque vs Current.png Model5d Torque vs Current.png There doesn't seem to be very much gain past the ...
by rhitee05
Feb 28 2012 8:52am
Forum: Motor Technology
Topic: Dual rotor axial flux motor design
Replies: 458
Views: 40070

Re: Dual rotor axial flux motor design

Increasing the volume by decreasing the inner radius will only help a little, as the iron between the magnets will tend to saturate first, though satruating the back iron isn't all that bad as long as there isn't any aluminum right behind it. That was my initial thinking as well, but after consider...
by rhitee05
Feb 27 2012 5:34pm
Forum: Motor Technology
Topic: Dual rotor axial flux motor design
Replies: 458
Views: 40070

Re: Dual rotor axial flux motor design

I have an overall length of 56mm, which is set by the length of my gearbox. The 28mm core height seems right - I'm happy with that. That leaves probably a maximum of 6mm for magnet plus back-iron height (43.5 mm over back-irons). I'll see if I can gain some more, though.... Trying to make sure I pr...
by rhitee05
Feb 27 2012 5:11pm
Forum: E-Bike Non-hub Motor Drives
Topic: Custom Two Stage Bottom Bracket - Is it Feasible?
Replies: 44
Views: 6898

Re: Custom Two Stage Bottom Bracket - Is it Feasible?

any idea what torque rating a human can put through the pedals? As an outside limit, it would be your weight (in kg) times g times the pedal arm... Pulling representative numbers, (100 kg)*(9.81)*(.17 m) = 167 N-m. That would be a peak number. You'd have to be on a recumbent to produce more than th...
by rhitee05
Feb 27 2012 1:39pm
Forum: Motor Technology
Topic: Dual rotor axial flux motor design
Replies: 458
Views: 40070

Re: Dual rotor axial flux motor design

Flux is 3D in the back-iron... Could we not increase the effective back-iron volume by reducing its inner radius? Yes, that should work at least to some degree. I'm not sure if it would be a straight volume improvement (i.e. is 12 mm wide x 4 mm thick equivalent to 16 mm x 3 mm), but probably at le...
by rhitee05
Feb 27 2012 12:22pm
Forum: Motor Technology
Topic: Dual rotor axial flux motor design
Replies: 458
Views: 40070

Re: Dual rotor axial flux motor design

I have an overall length of 56mm, which is set by the length of my gearbox. The 28mm core height seems right - I'm happy with that. That leaves probably a maximum of 6mm for magnet plus back-iron height (43.5 mm over back-irons). I'll see if I can gain some more, though.... We can treat this as a t...
by rhitee05
Feb 27 2012 11:11am
Forum: Motor Technology
Topic: Dual rotor axial flux motor design
Replies: 458
Views: 40070

Re: Dual rotor axial flux motor design

Can we get some idea of the iron-losses? It would be good to know max. Eta. I can try, but I haven't done that in FEMM before and I'm not sure how accurate it will be. I know that FEMM can't take into account the motion-induced eddy current losses, and the current-induced eddy losses it calculates ...
by rhitee05
Feb 26 2012 9:17pm
Forum: Motor Technology
Topic: Dual rotor axial flux motor design
Replies: 458
Views: 40070

Re: Dual rotor axial flux motor design

New set of model runs: N30EH magnets, 0.5 mm airgap, 6 mm wide x 28 mm long cores, 2x3t coils, and 1.3 mm dia steel pins in core ends. Obviously several of these parameters will be changed, as discussed, but these results are VERY promising. 3 mm thick magnets: Model4a Torque vs Current.png Model4a ...
by rhitee05
Feb 26 2012 9:43am
Forum: Motor Technology
Topic: Dual rotor axial flux motor design
Replies: 458
Views: 40070

Re: Dual rotor axial flux motor design

Thats cool its neet to see how torque goes down as you up current past I certian point. I proved this with my X5 last summer on my little dyno. But I dont understand the torque constant vs phas amps...? Why does it go down as you add phase amps? Well, if the torque output levels off or decreases fo...
by rhitee05
Feb 26 2012 9:31am
Forum: Motor Technology
Topic: Dual rotor axial flux motor design
Replies: 458
Views: 40070

Re: Dual rotor axial flux motor design

What magnet strength are you modelling for? I would prefer to use N48 with 0.75mm airgap and make the final adjustment by magnet thickness. The model is still using N30EH magnets. I can change to N48, make the airgap 0.75 mm, and then adjust thickness as needed. Narrowing down the configuration opt...
by rhitee05
Feb 25 2012 11:11pm
Forum: Motor Technology
Topic: Dual rotor axial flux motor design
Replies: 458
Views: 40070

Re: Dual rotor axial flux motor design

Hot off the presses:
Model3d Torque vs Current.png
Torque vs. Current
Model3d Torque vs Current.png (20.94 KiB) Viewed 347 times
Model3d BEMF.png
BEMF
Model3d BEMF.png (29.4 KiB) Viewed 347 times
These data are for the same model as before, except another tweak to airgap/magnet thickness.

I'm running a set of simulations overnight to check the 6 mm wide, 28 mm long configuration for 3 different magnet thicknesses.
by rhitee05
Feb 25 2012 8:47pm
Forum: Motor Technology
Topic: Arlo's power stage Leaf controller runs and drives page 103
Replies: 2595
Views: 195122

Re: Arlo's power stage....

Without snubbers the ringing on the drain-source has a peak of 150 V, with snubbers 70 V (both at 60 V supply). I put them in to prevent the 4115's from blowing up. You have a major inductance problem if you're getting a ringing amplitude 2.5x the supply voltage! Even with the snubber at 4 A you're...
by rhitee05
Feb 25 2012 8:22pm
Forum: Motor Technology
Topic: Dual rotor axial flux motor design
Replies: 458
Views: 40070

Re: Dual rotor axial flux motor design

There should just be room to increase the height of the cores by a couple of mm to 28mm. That would allow the height of the coils to increase from 9mm to 10mm. Perhaps try that first? Then, on top of that, see how it looks taking the neck from 5.5mm to 6mm width? I can only increase the radius 1mm ...
by rhitee05
Feb 25 2012 4:55pm
Forum: Motor Technology
Topic: Dual rotor axial flux motor design
Replies: 458
Views: 40070

Re: Dual rotor axial flux motor design

Just wondering whether you'd need to enter different x and y parameters? Could we not just assume uni-directional flux flow? Or is that too simplistic? In any case, one for the future - it doesn't work in favour of the immediate issue. Unfortunately, yes. The defining characteristic of the grain-or...
by rhitee05
Feb 25 2012 2:14pm
Forum: Motor Technology
Topic: Arlo's power stage Leaf controller runs and drives page 103
Replies: 2595
Views: 195122

Re: Arlo's power stage....

There's really little point to using an RC snubber on MOSFETs. The snubber serves to reduce the dv/dt when the MOSFET switches, which has the effect of slowing down the switching. You could get virtually the same effect by increasing the gate resistor, which is much simpler. Either way the ringing i...
by rhitee05
Feb 23 2012 7:55pm
Forum: Motor Technology
Topic: Dual rotor axial flux motor design
Replies: 458
Views: 40070

Re: Dual rotor axial flux motor design

The alternative would be to increase the core to 5.5mm, which would leave 2mm either side for 2x3t or 2x4t... That's definitely on the list of configurations to try as well. The end result will likely be a combination of both, more iron and lower static flux density. Hm, is it "normal" that Kt decr...
by rhitee05
Feb 23 2012 5:15pm
Forum: Motor Technology
Topic: Dual rotor axial flux motor design
Replies: 458
Views: 40070

Re: Dual rotor axial flux motor design

The updated geometry is definitely an improvement. I left the magnet thickness and air gap alone for now and changed the windings to 2x4 for 8 turns per core. This resulted in a Kv of 155 RPM/V. I ran a very limited number of currents, but this configuration produced something like 2.2 N-m at 50 A. ...