high voltage micro motor

[hvmicromotor]

Does anyone know of a manufacturer that makes a HV micro motors and generators ? Something similar in size to what the typical multirotor copters use? example of typical motor specs,

http://www.hobbyking.com/hobbyking/...tar_4340_500kv_Brushless_Outrunner_900w_.html

Im wanting to build a gas powered multirotor and have the engine run a generator that will power the individual motors on each prop. Typical motors that are standard use around 800 watts each. Im hoping for a 8 prop octocopter (8 x 800 = 6400 watts) but a 6kw HV generator will probably be harder to find than the motors. Even a quad copter is still at 3kw. Im thinking if I up the voltage I can reduce the amps and get the same results of thrust and keep the weight down.
I have a 200 pound 5kw gas generator and I cant imagine getting 6 kw form a device that weighs a couple of pounds even at 480 volts..
Or maybe there isnt any and thats why there are no gas powered mutirotors?

any constructive comments?

thanks


wishfull thinking

 

[itsmoked]

Interesting proposal. I don't think it will fly though..

You're running an engine that needs fuel and oiling and controls => weight.

Then you need 8 motors => weight.

Then you need a generator => weight.

You essentially are trying to use 8 prime movers plus another - the engine. You're losing your payload wholesale.

Have you considered driving the 8 rotors directly from the one prime mover? Make the props controllable and use that for your vector control. That would dump 8 heavy motors and a heavy generator.

Usually one doesn't grab for the primemover->generator->motors solution unless low speed high torque is needed. Things like quarry dump trucks, or locomotives, or draglines.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[hvmicromotor]

Thanks Keith,
Have you visited any web sites and looked at multirotor copters? These are small toys / professional aerial platforms used for fun or search and rescue or photography. They price from $30 to $30,000. They are from 6 inches across to 3 feet across in size. They have 3 to 8 motors. They have cameras mounted on them so when you fly it you can see everything from the copter as if you were in it.

They operate by controlling the speed of each motor individually.

I dont want to reinvent the wheel just add fly time to it. Right now the typical fly time is 15 to 30 minutes. When you are looking for someone's lost child in the mountains you need more fly time.

Thanks for your input,

 

[mikekilroy]

Your 6kw is a tad off my friend!

DO go study what is being done. Top of the line is dji.com at $1.2k or their just announced Inspire 1 at $ 1800.00.. ck their battery size.... It flies for about 10 minutes.

I just bought a starter unit, the UDI 818A with real time camera and FPV.... its batt is 3.7v, 500mah, and flies about 6 minutes.....

These puppies go up like 2-3000 feet, each have HD camera load....

Just curious how you get to 6kw from THAT?

http://www.KilroyWasHere<dot>com

 

[mikekilroy]

Typical motors that are standard use around 800 watts each

Ah... here is your error.... these little guys will fly using around 3-4 amps @ 3.7v; that is 10-20 watts - TOTAL - for all the motors, whether quadcopter or more. So for 4 motors, that is like 3-4 watts.

This is more in line with ratings and capability of these small 1" dia motors.

Granted, these hi energy density lipo batts make it possible to pull high peaks. It is such a balancing act of energy density to weight that it is most often a loosing battle to add larger batteries to try to get longer flight time.

If a gas engine could produce enough energy density to fly more than 5-15 minutes, don't you think the multimillion dollar quadcopter companies like dji with huge r&d budgets would do it?

http://www.KilroyWasHere<dot>com

 

[logbook]

I'm thinking if I up the voltage I can reduce the amps and get the same results of thrust and keep the weight down.

I believe you have gone wrong at this point. If you double the voltage you can indeed halve the current for the same power. This can give the same thrust. But you have gone on further to suggest that by reducing the current you will reduce the weight. That is true of overhead power cables (which get thinner for lower current) but is not true for a motor. Twice the length of wire with half the cross-sectional area gives the same weight.

Heli engine
This is a very nice engine (from my inexperienced viewpoint). It puts out up to 3.75HP (=2.8kW). In order to make it into a generator you essentially connect it to a motor (which you drive and therefore makes it into a generator).

Have you considered driving the 8 rotors directly from the one prime mover?

This is not such a bad idea. I know you don't want to "re-invent the wheel". But using the engine to drive most of the main thrust and using the other rotors for balance would be much more power efficient. Using a petrol engine to generate electricity which you then use to drive a motor is pretty bad.

At work we have a large lithium battery pack for outdoor applications. People will insist on plugging mains inverters into it to get mains power (230V) then using standard laptop power supplies to get the low voltage for the laptops! This gives at best 80% efficiency to get the mains and then another 80% down to laptop voltage, overall only 64% efficient. That is not the way to extend battery life. Going from shaft power to generator to motor is even worse because of the excess weight as itsmoked has said.

 

[waross]

This may be a good match if used with the Heli-engine suggested by logbook. Used as a generator it should absorb about 3.5 HP.

http://www.hobbyking.com/hobbyking/store/__17698__XK4082_1500KV_Brushless_Inrunner.html

Check the weights against the battery weight required for your machine and estimate if it will fly.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[davidbeach]

Ok, nobody's brought it up yet, but I doubt that there are any high voltage motors anywhere, anyplace, for any application. HV doesn't even start until you get above 69kV. Even a MV motor would be tremendously heavy due to the necessary insulation. Anything less than 1kV is low voltage. But as stated above, I'm pretty sure that more batteries will give far more flight time than the same weight of fuel, prime mover, and generator.

 

[ScottyUK]

Hi David,

In the rest of the world where IEC rules apply there is only Low Voltage and High Voltage. Low voltage covers the range from zero up to 1000V AC or 1500V DC, and anything which isn't low voltage is considered high voltage.

I still think of MV as between 3.3kV and 66kV, but the term has no officially-recognised meaning.

 

[logbook]

Used as a generator it should absorb about 3.5 HP.
brushless inrunner

I kind of glossed over the whole business of using a motor as a generator since I was more interested in the power and weight issues. This definitely works for non-electronic motors. But I am really not sure if a brushless (electronically commutated) motor is guaranteed to work in that way -- or indeed if any of them work that way. Anyone know?

 

[mikekilroy]

I kind of glossed over the whole business of using a motor as a generator since I was more interested in the power and weight issues. This definitely works for non-electronic motors. But I am really not sure if a brushless (electronically commutated) motor is guaranteed to work in that way -- or indeed if any of them work that way. Anyone know?

yep, works just as well as gen as mot. no electronics needed (other than output rectifier)

http://www.KilroyWasHere<dot>com

 

[micromotor2]

mikekilroy (Electrical)
14 Nov 14 18:58
Typical motors that are standard use around 800 watts each

Ah... here is your error.... these little guys will fly using around 3-4 amps @ 3.7v; that is 10-20 watts - TOTAL - for all the motors, whether quadcopter or more. So for 4 motors, that is like 3-4 watts.

This is more in line with ratings and capability of these small 1" dia motors.

Granted, these hi energy density lipo batts make it possible to pull high peaks. It is such a balancing act of energy density to weight that it is most often a loosing battle to add larger batteries to try to get longer flight time.

If a gas engine could produce enough energy density to fly more than 5-15 minutes, don't you think the multimillion dollar quadcopter companies like dji with huge r&d budgets would do it?

http://www.KilroyWasHere<dot>com

Thanks Mike and I guess so. Then again if you raised the voltage to a dangerous level the liabilities would prevent them from going there. So I believe it is possible just not safely for a non electrical type of person. This isnt something I want to sell. I want to use it personally. For everyone who has commented on the term "high voltage" I meant "higher voltage" anything higher than what they currently are using in quad copters lipo batteries. I dont know where the trade off would be (voltage vs current) but I cant help but imagine it is doable. And even keep the lipos and maybe and use them paralleled for the surge issues. Does anyone know of a neodymium generator that is small?

I really appreciate everyones input! anyone want to tackle this together? You would be famous...maybe not. ;^)

 

[IRstuff]

Once your voltage overcomes the circuit parasitics, increasing voltage doesn't really buy you much. Motors have been around for a long time; lots of people "can't help but imagine it is doable," to somehow dramatically increase performance but that's always in a field that they're not expert in. Not unlike other disciplines that "can't help but imagine it is doable" to develop "something" that can aid passive isolation systems to minimize sway space without jacking the natural frequency up.

Given that the experts in motor design, who aren't even necessarily anyone that's responded to this thread haven't succeeded suggests that it's just not that easy for someone out of left field to make the improvement.

Maybe you'll get lucky, but the statistics are not in your favor.

TTFN
faq731-376

Need help writing a question or understanding a reply? forum1529

Of course I can. I can do anything. I can do absolutely anything. I'm an expert!

 

[mikekilroy]

micromotor2, why did you change your name from hvmicromotor?

Then again if you raised the voltage to a dangerous level the liabilities would prevent them from going there. So I believe it is possible just not safely for a non electrical type of person. This isnt something I want to sell. I want to use it personally.

Hogwash and nonsense. Liability has nothing to do with any discussion here.

You state you have an electrical background. Anyone with electrical education can tell you your statement above is 100% false.

P=V*I. Power is volts x amps in lay terms sir. That means that if you double the volts, the current for the same power will be 1/2.

Put into battery or generator terms, two pc. 3.7volt lipo batteries capable of 0.1amp for an hour can be put in series or parallel. In series, they are 'higher voltage' at 7.4v and still capable of producing 0.1amp for an hour. IN parallel, they are 3.7v and capable of producing 0.2amp for an hour. SAME ENERGY OUTPUT.

If you want to believe 'higher voltage' will get you longer running time, ok. But the fact of it is NOT.

http://www.KilroyWasHere<dot>com

 

[Mobius44]

Gas powered helicopters are already available and could provide the extended flight time you want. They might be more difficult to fly than the multi-rotor design, but that's an easy problem to solve with a little practice. I'm sure you can figure out how to add a larger gas tank and camera.

Here is an example of a couple kits I found on the Internet:

http://www.centuryheli.com/products/helikits/gas.htm