12 kw rc motor

[CroDriver]

So now I need to get a 6 fet programible bord with varible regen coming! Anyone know of one that doesnt use the throtle for the varable part?
I have almost all the stuff I need to get this done! Special thanks to my sponcer :wink:

You'll be driving the motor with IGBTs? Cool 8)

600 Amp?

 

[Arlo1]

So now I need to get a 6 fet programible bord with varible regen coming! Anyone know of one that doesnt use the throtle for the varable part?
I have almost all the stuff I need to get this done! Special thanks to my sponcer :wink:

You'll be driving the motor with IGBTs? Cool 8)

600 Amp?

No the things just below the big caps are Big 680 amp dual leg fets! And below that is some very cool heat syncs and some teflon!

 

[rebelpilot]

Note 1: Because BEMF is proportional to the rotor speed, this implies that the rotor should
turn at a minimum speed to generate sufficient BEMF. This minimum speed varies from one
motor to another. For very low speeds it may be required to amplify BEMF in order to control
the motor. This is presented in the appendix of this application note.

View attachment 10401.pdf
Is sensorless control of this motor with existing rc controllers possible by amplification of the BEMF signal?

 

[Arlo1]

Note 1: Because BEMF is proportional to the rotor speed, this implies that the rotor should
turn at a minimum speed to generate sufficient BEMF. This minimum speed varies from one
motor to another. For very low speeds it may be required to amplify BEMF in order to control
the motor. This is presented in the appendix of this application note.

Is sensorless control of this motor with existing rc controllers possible by amplification of the BEMF signal?

Only if you can run it with out load. Once you put a load on it it will pop controlers faster then you can afford them!

 

[Arlo1]

I think my ceramic balls are here I will go find out and see if I can fit them tonight!

 

[rebelpilot]

Only if you can run it with out load. Once you put a load on it it will pop controlers faster then you can afford them!

Isn't this because the controller is not synchronizing?

 

[rebelpilot]

I don't have a motor to test but I suspect that if there is no load (or only the frictional load of the bearings) that the motor will run smoothly without being synchronized, and as soon as any load is applied that is large enough to cause the rotating portion to lag the field.... bang. Commutation error.

 

[Arlo1]

I don't have a motor to test but I suspect that if there is no load (or only the frictional load of the bearings) that the motor will run smoothly without being synchronized, and as soon as any load is applied that is large enough to cause the rotating portion to lag the field.... bang. Commutation error.

Im not so much the guy to ask because I am just listening to what I was warned! Luke (livefor physics) will tell you all about it. We have many electrical engineers on this forum who have comented on the motor and said it will be a controller nightmere!
I have had it running with my 18 fet sensored controler but I have some MEGA Mostfets to build a MEGA controler!
I am not tacking chances on blowing controlers its not just $300 ish in money its the 10-20 hours I spend to build a controler properly I dont feel like wasting!

 

[liveforphysics]

I don't have a motor to test but I suspect that if there is no load (or only the frictional load of the bearings) that the motor will run smoothly without being synchronized, and as soon as any load is applied that is large enough to cause the rotating portion to lag the field.... bang. Commutation error.

It's not related to a synch loss or commutation error (unless you're trying to run it sensorless... lol). The sensored controllers stay in sensored mode always. Sync loss isn't the concern.

The problems in driving it are do to the extremely low resistance and inductance of the motor.
This isn't a fault of the motor, it's simple the nature of scaleing up an RC style motor, and keeping the winding ratios similar etc.
Ultimately it's the path to increadible motor performance, it just means controllers need to develop to keep up with the motor. At least 4 folks on this forum are actively working towards reaching that goal.

 

[Arlo1]

Im playing with my black shiny balls! I'll have pictures for you guys later

 

[Anonymous]

How are the balls doing have you done it yet
thx

Im playing with my black shiny balls! I'll have pictures for you guys later

 

[markobetti]

haahah

 

[Arlo1]

Haha yup the balls I ordered do fit well I till try to get pictures up when I can I am out of town for the weekend helping a friend race his rally car

 

[Arlo1]

IM going to go with 12 balls! And I will build a retainer with teflon luke gave me this week!

 

[liveforphysics]

Sweet. 12 balls should be more than enough.

If you want me to CNC out a teflon ball cage, download google sketchup, design it, and email me the file.

 

[Arlo1]

Sweet. 12 balls should be more than enough.

If you want me to CNC out a teflon ball cage, download google sketchup, design it, and email me the file.

I tried to play on google scetch up this weekend but I think it will be quicker to cut one on the lathe my self. I will let you know luke. Its going to take some time for me to lern google scetch up well.

 

[grandmasterE]

http://sketchupforwoodworkers.com/tutorials

This won't be everything you need, but after watching those tutorials you should be able to do some interesting stuff.

E

 

[Arlo1]

http://sketchupforwoodworkers.com/tutorials

This won't be everything you need, but after watching those tutorials you should be able to do some interesting stuff.

E

Thanks man. for me its just a matter of getting the time to lern it. I always seem to have a lot on the go.

 

[toolman2]

when your up and running agian arlo, could you do the rpm check for us on 97v, i still cant get my head around this motor doing 8000 rpm (without pain).
even with the new ca120-70 hobbycity motor people are begining to see the real (eddy losses etc) rpm limits of these 120mm+ motors being closer to 5000rpm -ie the skirt bearing rpm limit is a non issue and 100ish kph magnet speed is toward the max.

but remember arlo, if you got to 8000 even with 17amps, its a massive breakthrough..

 

[Arlo1]

when your up and running agian arlo, could you do the rpm check for us on 97v, i still cant get my head around this motor doing 8000 rpm (without pain).
even with the new ca120-70 hobbycity motor people are begining to see the real (eddy losses etc) rpm limits of these 120mm+ motors being closer to 5000rpm -ie the skirt bearing rpm limit is a non issue and 100ish kph magnet speed is toward the max.

but remember arlo, if you got to 8000 even with 17amps, its a massive breakthrough..

Yes I should correct that 8000 is a number based on an educated guess based on miss informantion. If this motor is 75kv then 100 volts is 7500 rpm I was understanding my contoler advanced the timing and got more but Im betting its just the wave form that gets modified in my controler on the 120% setting as Jeremy pointed out earlier!

On another note I will do what I can as soon as I can. My boss had to drive $1,000,000 worth of nitro harleys to the US and left me to run his 3 buisnesses and I run mine on evenings and mondays on top of that and just tonight put an offer in on a house.
Needless to say I havent had much sleep lately and Im in the middle of a lot of work lol.
I hope to have my buisness caught up by end of day monday then back to collossus and I will use my Osilloscope to determine the RPM.
I will try to cut a few rings for the retainers tomorow on the lathe!

Realisticly I expect 7500 rpm at 100 volts unloaded if its a 75kv motor and you put 100 volts to it at full throtle and it gets stuck at 5000 rpm the amps should hit the max of the controler or bateries which is ~330amps with my set up!

 

[liveforphysics]

When you're cutting that teflon on the lathe, I would first turn a ring section with edges the bow out to match the races, and give maybe 0.01" clearence between the ID/OD of the races. Then drill the 12 holes in the race that are slightly bigger than the balls themselves, so it cuts the sections of race for you. And then run the parting tool down the back side to cut the chunks off the slab. Should end up with 12 pieces that you have to give a little pop with a hammer to knock them into the race, which I think is what you want for this.

 

[Arlo1]

When you're cutting that teflon on the lathe, I would first turn a ring section with edges the bow out to match the races, and give maybe 0.01" clearence between the ID/OD of the races. Then drill the 12 holes in the race that are slightly bigger than the balls themselves, so it cuts the sections of race for you. And then run the parting tool down the back side to cut the chunks off the slab. Should end up with 12 pieces that you have to give a little pop with a hammer to knock them into the race, which I think is what you want for this.

How about a hybrid plan of what you said and what I was origanly thinking lol.
I will make it one sided so the balls click into one side then the retainer is held in the races by the size of the bow where it clicks into the ball grooves and this way I should be able to make 2 at once with the chuck you gave me!

 

[liveforphysics]

1 sided should be great too, I was just thinking multi-piece would be easier to make, but I know you've got the skills to crank out some crazy stuff.

 

[Arlo1]

I might make another 1 Im a little afraid of the peices of teflon coming out. It was ment to be a one peice but because I made it just slightly to skinny and its real trick to make it that small I ending up with 6 balls and 6 peices!

 

[liveforphysics]

Kick ass! That bearing is going to be super low drag. Nice work!