# Making my own 100Kw+ BLDC motor ?



## Salty9 (Jul 13, 2009)

I don't think you could scale up a small rc motor by that amount. A thousand amp controller would not be trivial either. 

Be sure and consider the heat generated by the motor. Magnets are demagnetized by higher temperatures. 

Good luck.


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## elmerfud (Oct 29, 2008)

http://www.youtube.com/watch?v=prRsJm5lAzc

http://www.youtube.com/watch?v=E7qZYKbCJCw

http://www.youtube.com/watch?v=9pL2qDbPqw8&feature=related


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## elmerfud (Oct 29, 2008)

Salty9 said:


> I don't think you could scale up a small rc motor by that amount.


 What makes you say that ? What SCIENTIFIC principle would prevent it from scaling ?



> A thousand amp controller would not be trivial either.


 Nobody said anything about "trivial".

http://www.youtube.com/watch?v=o6tARHclfds&feature=related


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## Evilsizer (Jan 25, 2010)

why not go small scale first, for a prototype. say like a 10kw for a single person scooter or some thing like a mini-motorcycle. that way you can test it out and then make adjustments if needed. i always think its best to start smaller first to learn about it, if you dont have hands on experience. then scale it up from there..


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## crap (Dec 5, 2009)

Dunno where to find a stator that fits, but besides that I think a 100kW outrunner seems like an interesting idea. Especially if it is made to output very high torque, so it could be used for direct-drive applications. If you know how to do it then why not try?

the software FEMM can be used for a lot of calculations in the area. There is an example of this here (an LRK outrunner analyzed):
http://www.femm.info/wiki/LRKAnalysis


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## samborambo (Aug 27, 2008)

elmerfud said:


> I need a large BLDC motor for a project. I want it to be a BLDC motor because the controllers are easier to build and they have better torque characteristics than some other types.


Easier than what? A BLDC controller is essentially the same hardware as a 3 phase induction motor controller.



> The model airplane community builds their own BLDC motors all the time. See rcgroups.com for more into. They also build their own BLDC motor controllers.


Building a <15VDC <100A controller is a lot simpler than designing a high voltage, high current one - especialy considering the gate drive and feedback isolation. When you start getting into >500A, go and talk to Tesseract, the designer of the Solution 1. He'll quickly put you off any notion of the design being trivial.



> The power to weight ratio of the large RC BLDC motors is incredible. An 11 Kw motor might only weigh a few Kg.
> 
> I'd like to build a 100 Kw outrunner. I'd like to use the rotor from a single or 3 phase AC motor as the stator for my outrunner. Of course I would have to rewind it. The RC guys rewind their stators all the time.


Pay attention to the speed at which these model aeroplne motors develop their power. I'm betting around 50-60,000RPM. That's not much torque. You'll need a multiple stage reduction drive to make any use of that power.

The rotor of an average induction motor has cast aluminium bars forming the squirrel cage over an axially laminated core. They're not really windings, as such, just shorted rings. Good luck with that.

A custom wound 12" AC induction motor can produce 100kW+ peak power at around 5000rpm. Much easier.



> The Rotor would be a can type with magnetic bars held inside. Just like the RC motors.
> 
> That is as far as I've gotten. Comments ? Advice ?


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## elmerfud (Oct 29, 2008)

samborambo said:


> Easier than what? A BLDC controller is essentially the same hardware as a 3 phase induction motor controller.


You might want to do some reading. The software is very different.





> <snip>
> Pay attention to the speed at which these model aeroplne motors develop their power. I'm betting around 50-60,000RPM. That's not much torque. You'll need a multiple stage reduction drive to make any use of that power.


Kv of 180-250 on the larger model airplane motors. On a 48v supply thats 8640 to 12,000 RPM. Not a big problem. 

I'm not going to answer the rest of the questions.


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## automd (Feb 5, 2010)

Evilsizer said:


> why not go small scale first, for a prototype. say like a 10kw for a single person scooter or some thing like a mini-motorcycle. that way you can test it out and then make adjustments if needed. i always think its best to start smaller first to learn about it, if you dont have hands on experience. then scale it up from there..


I agree. This would be the safest way to go.. well, for now. As you progress along & became confident to take these major adjustments then it'll be alot different.



> Building a <15VDC <100A controller is a lot simpler than designing a high voltage, high current one


Really! So better be careful bro


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## RoughRider (Aug 14, 2008)

man...do you realy thing...to buiild a outrunner with 100kW of power is a walk in the park???

if it would be SOOOOO easy, everyone would do it...

i have seen many people on forums, who had no idea of electric motors and wanted to build WORLDs best motor...they all failed...

your project is not realistic...

here is a big outrunner:

http://www.diyelectriccar.com/forums/showthread.php/600-series-outrunner-motor-enertrac-38486.html

30kW peakpower at around 20kg weight...

but i know, you can do MUCH better...right?


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## Amberwolf (May 29, 2009)

There is currently a DIY motor design challenge running over at Endless Sphere. While none of the designs are intended to be anywhere near this power level, there are a number of different concepts, approaches, and lots of design info being gathered there, most of it now under the new Motor Technology subforum. 

Additionally, there are a few modifications of "standard" ebike BLDC controllers that run up to around a tenth to a seventh of the power level you're looking for, so perhaps you might want to take a look at what they are doing, but to consider IGBT instead of MOSFET use for higher voltages at lower current levels. 

Other than that, all I can say is "Good luck!" 
________
VOLCANO VAPORIZER


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## samborambo (Aug 27, 2008)

elmerfud said:


> You might want to do some reading. The software is very different.


 Really? And which software would this be? Hall sensor reaction based phase commutation? Vector based field orientated control? V/Hz? Quite easy to make a vague statement like "the software is very different". The software *can* be very different. There are at least half a dozen different control schemes for induction machines and most can also be used for PM machines. 

The best control scheme for dynamic torque response is sensored vector based field orientated control. For that control scheme, the only major differences between controlling an induction motor and controlling a PM motor are that the torque vectors are of the same magnitude in PM commutation and in induction commutation there is also slip gain to take into account.

Besides, I stated that the HARDWARE is essentially the same. For sensored closed loop control of PM motors the only addition is the hall sensor for magnet position sensing.

I suggest YOU do some reading.



> Kv of 180-250 on the larger model airplane motors. On a 48v supply thats 8640 to 12,000 RPM. Not a big problem.


So at 12000 RPM the motor would need to source at least 80Nm of torque. Multistage gearbox and low BEMF at low speed means that motor still wouldn't be very efficient. Might as well stick with DC series wound motors.



> I'm not going to answer the rest of the questions.


That's excellent news.


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## ev_nred (Sep 23, 2009)

just asking are there any bldc motors this strong on the market today or in a few years 
thanks,
ev_nred


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## Nathan219 (May 18, 2010)

Remy makes a 100KW motor. BLDC motors are great until they demagnetize Good luck!


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## pm_dawn (Sep 14, 2009)

The YASA is a BLDC and has 100KW peak liquid cooled.
Its not an outrunner though.

http://oxfordyasamotors.com/


They use Sevcon Evo5 controllers for that motor.

Regards
/Per


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## jk1981 (Nov 12, 2010)

elmerfud said:


> What makes you say that ? What SCIENTIFIC principle would prevent it from scaling ?


Would you scale the airgap too, or just the rest of the geometry? Ok, so you could maybe scale a small RC outrunner design 25, 50, maybe even 100% diametrically and still get it to provide some sort of performance but there comes a point where you're realistically going to have to start changing the airgap, stator and adding teeth/poles. At that point you're not merely scaling a design, you're significantly altering it and the choices you make will have a significant impact on performance. For example: Can your inverter work at the frequency required to give you the RPM you need? Can it handle the inductance? Have you introduced a new vibration problem by adding teeth/poles or changing dimensions? Will it cool properly at its new lower operating speed (most high output? RC motors I've seen/used fan cool quite well but then they basically only ever run under load for any time at very high RPM or at least they do in an aircraft/heli/boat).

Scaling lengthwise you'll be similarly limited by rigidity/vibration, cooling and assembly problems without a significant redesign.

There's no technical reason why you can't build a 100+kW PM outrunner but you won't build a good one by simply scaling up a 1kW RC motor or even a huge 10kW design. In fact by the time you get to the size and weight you need to produce 100kW by simply scaling you'll probably have used the materials and space to required build a properly designed 500kW motor


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## modern_messiah (Dec 8, 2010)

I'm one of the guys over at the endless-sphere forums looking and building my own Axial Flux Motor. I am *starting *small and once I get the motor working (plus hall sensor control using an OTS controller) I will take stock and start on my ultimate goal of building a multi-stage AF motor.

Read: far greater than 100kW – however this will be obtained by effectively daisy-chaining 3 motors together; not one all powerful motor...

I'm no chump (I'm an Aerospace Avionics Engineer by profession) and I can tell you _right now_ that I have totally abandoned the idea of building my own controller. In fact my multi stage engine will be designed around my chosen controller...when I get that far; baby steps and all that.

I’ve researched my a*se off , I’ve done the maths, I’ve used FEMM to model various possible designs, I’ve redrawn my models more times than I care to count and all I can say is that you should try listen to what people are telling you here in this thread – especially samborambo. 

I could be wrong but it appears that you signed up to these forums purely to ask questions about your motor – please don’t get narky if people don’t respond in the way you envisaged. If you took the time to digest what is being written you will save yourself a lot of time and money. 

I guarantee it.

If you’re serious about doing this properly check out the Endless-sphere forums - much better technical information over there. These forums tend to focus on the vehicle build itself rather than the real nitty-gritty of the technology behind them.


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