speedmd
10 MW
Time scales are very different and the area under the curve appears much greater on the 28 pole BEMF trace. This all is fighting the controllers ability to deliver its wave form, is it not?
John in CR said:Can you explain the obvious part, down to a level where I might be able to grasp it. How does it show up in the pdf's you shared? Is it in the flux density section or the way the back EMF seems to fit better with 28 poles? Doesn't the flux linkage waveform look much better with the 20 pole?
bearing said:John in CR said:Can you explain the obvious part, down to a level where I might be able to grasp it. How does it show up in the pdf's you shared? Is it in the flux density section or the way the back EMF seems to fit better with 28 poles? Doesn't the flux linkage waveform look much better with the 20 pole?
I have been wrong all along, sorry.
Can you post the pictures or screen shots? I looked and I think its not the same as hooking a scope between 2 phase wires. I think the flux linkage is what you will see from a scope hooked to 2 phase wires. The back emf I seen in your files said Back emf with harmonic... and did not look like what you will see from a scope hooked between 2 phase wires... Maybe I'M not looking at the right image?bearing said:If you look at the BEMF waveform, you can see that the 28 pole has a much more trapezoidal shape. So to me, it looks like the 28p is more suited to 6-step controller.
I don't know what flux linkage is, to be honest.
Arlo1 said:Can you post the pictures or screen shots? I looked and I think its not the same as hooking a scope between 2 phase wires. I think the flux linkage is what you will see from a scope hooked to 2 phase wires. The back emf I seen in your files said Back emf with harmonic... and did not look like what you will see from a scope hooked between 2 phase wires... Maybe I'M not looking at the right image?bearing said:If you look at the BEMF waveform, you can see that the 28 pole has a much more trapezoidal shape. So to me, it looks like the 28p is more suited to 6-step controller.
I don't know what flux linkage is, to be honest.
Yes, Kv on it's own doesn't tell you much, it's Kv in relation to Rm that's important. What I was struggling with is that, if increasing the pole count lowers Kv without increasing Rm then, you must get more torque for the same copper losses.Biff said:The second thing to note is that Kv has nothing to do with how much torque the motor can produce. allright, that may seem a little misleading, because obviously the amount of torque that a motor can produce is defined by Kv AND how much current your controller can deliver. When it comes down to it, if you are pushing your motor to the limit of its ability, kV just defines how much current you need your controller to deliver to get the motor to produce the torque you want. A motor's maximum torque will be defined either by saturation of the iron, or when flames erupt from the coils, a good design will have both of those happen around the same current . You can change the number of turns on a motor all you want to get it to have the Kv you want for your system, but you will not change the maximum amount of torque that the motor could deliver, if you always fit about the same amount of copper in each slot.
Because there is only one winding symmetry?Biff said:Arlo asked why not have a 24tooth 22pole tooth design. That is a good magnetic design, I don't know why they wouldn't pick that combination.
Actually I was asking for 20 magnets with 24 teeth but the winding factor for 22 magnets and 24 teath is a bit better. As far as I'm concerned lower magnets is better for now you will have a weight penalty because lower magnet counts will need thicker back iron (outer can) but if I had to chose between a 4kg paper weight or a awesome 4.5kg motor that can be run with a cheep 24 fet what do you think I would do? It doesn't make sense to force people to buy $1000+ controllers for a simple change like this. Yes I admit inductance will be a roll in either motor but as cheaper sine and more advanced china controllers come out they will be limited in the max electrical frequency... So I think Marko and Hall and Accountant need to understand they can make a motor that will sell if controllers are cheaper for it!Miles said:Because there is only one winding symmetry?Biff said:Arlo asked why not have a 24tooth 22pole tooth design. That is a good magnetic design, I don't know why they wouldn't pick that combination.
possiblyMiles said:Because there is only one winding symmetry?Biff said:Arlo asked why not have a 24tooth 22pole tooth design. That is a good magnetic design, I don't know why they wouldn't pick that combination.
Arlo1 said:So I think Marko and Hall and Accountant need to understand they can make a motor that will sell if controllers are cheaper for it!
John in CR said:Biff,
Thanks so much for sharing all that. Very interesting about the tooth geometry. Once the design is good, can you increase the stator and magnet lengths and expect the same good result but higher power, or are you back to only somewhere between revision 1 and 40?
bearing said:Thud said:"magnetic gear ratio" nonsence
Probably not nonsense. You obviously get more torque (per amp) with more poles, with no penalty in added winding resistance. But the peak "saturated" torque might not rise with more poles, if Biff is right. So if you are looking to use the motor at the absolute max, more poles may be a disadvantage. That's how I conclude the latest "news" on endless-sphere
What Im getting at is with a rewind and using a sevcon for instance you are still limited to 400hz which is 1714 rpm max so what was that about max phase amps..... You can only build so much HP at 1714 rpm.... Yes the china controllers will run higher E-rpm. And some of us are still trying to bring a cheep controller to the game... BUT if I was going to bring a motor to market It would be something easier to run and as far as I'm concerned the new 28 poll 24 slot motor is harder to run not easier.toolman2 said:bearing said:Thud said:"magnetic gear ratio" nonsence
Probably not nonsense. You obviously get more torque (per amp) with more poles, with no penalty in added winding resistance. But the peak "saturated" torque might not rise with more poles, if Biff is right. So if you are looking to use the motor at the absolute max, more poles may be a disadvantage. That's how I conclude the latest "news" on endless-sphere
Yes you did great. Im just using sevcon as an example. But so far you gave used the only controller that can be bought for less the $2000 I can find...SplinterOz said:I didn't buy it to go slow. So
110km/h on a full motorbike with a controller cheaper. than your sevcon.
I think Splinter got his controller for < $1000 ( we will wait for him to chime in) its the only one so far although it should not be long until more are available. But one Sine controller from Kathy on the forums here can't do it because of the E-rpm problem....swbluto said:So, can someone tell me the cost figures for running this motor?
$600 motor + $3000 controller?
The 72volt 600amp controller for under 1000 and the 700amp for 1100 will get you to 14kw (rear wheel). Now this is with prototype motor,toolman2 and I have confirmed that the new one (I have an air cooled one) should get close as I am probably just short of saturating the current model.swbluto said:So, can someone tell me the cost figures for running this motor?
$600 motor + $3000 controller?
This should be even more of an advantage with smaller motors and their correspondingly shorter thermal time constant. Kt falls off the closer you work to saturation, though - that might temper the gain a bit. I haven't completely got my head around pole count WRT saturation, yet........ :|toolman2 said:you get more efficient torque production from these high pole count motors, of course your right miles that you get more NM per amp this way without added ir so thats how its done.
but the peak torque (saturation limited) does not rise with it, so you end up with a motor that has very little difference between the max continuous torque and the max peak torque.....
Decreases, you mean?bearing said:I'm still unsure whether pole count increases kv.