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Old Apr 06, 2012, 06:48 PM
Hey Ya'll!! Watch THIS!!
Michael Paxton's Avatar
Nashville TN.
Joined Mar 2006
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When they give you volts and amps, they are giving you the recommended power rating of the motor.
Unless the bearings are just crap, it doesn't matter how you get to that power level. ie: high voltage or low voltage higher amps.
higher volts is more efficient of course.
And these motors are in the duct of an EDF. So they get better cooling than say an onroad electric car.
Hope this helps.
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Old Apr 06, 2012, 07:03 PM
3DHOG
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Joined Sep 2010
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think you meant higher voltage and lower amps is more efficient didn't you?
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Old Apr 06, 2012, 07:12 PM
Hey Ya'll!! Watch THIS!!
Michael Paxton's Avatar
Nashville TN.
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Quote:
Originally Posted by jcdfrd View Post
think you meant higher voltage and lower amps is more efficient didn't you?
Uh.....Yup! LOL
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Old Apr 06, 2012, 07:14 PM
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United States, OH, Dresden
Joined Mar 2004
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Motor Voltage/Amps

Ok, Question.
I have a ARC 28-47-2150- 3 cell 40 max amps and I had asked Dave if I could run more cells he said no.
But yet I've seen on here people using motors with 11.1 volt rating with I beleive it was 35 amp max .
So could I get by running a 5 or 6 cell pack on it .
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Old Apr 06, 2012, 07:28 PM
Hey Ya'll!! Watch THIS!!
Michael Paxton's Avatar
Nashville TN.
Joined Mar 2006
2,555 Posts
Are you are willing to destroy it testing it?
If Dave says no......I guess that means he washes his
hands of any repairs or replacement if you do.destroy it.
His site states that like all ARC motors you can run more power thru
them as long as you keep them cool.
But....
It's your motor. Have fun!
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Old Apr 06, 2012, 07:34 PM
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USA, NY, New Hampton
Joined Jan 2005
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Hey guys I'm upgrading my Dynam Meteor to the cs10 and was wondering which motor to use?
I would like to run it on 4s 3000. I know hk is out of the preferred motor so what to use, I don't need blistering speed some where over 100mph would be nice. thanks Jim
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Old Apr 06, 2012, 07:37 PM
Extreme CNC Alloy EDF
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Australia
Joined Mar 2006
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The 2847 will take 50-60 amps if its well cooled, in an alloy housing I think it would run on 6s at 55-58 amps with the CS rotor. 5s should be a breeze. of course there are no guarantees on 6s, the user and the situation at the end of the day will dictate how hot things get...
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Old Apr 06, 2012, 07:38 PM
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Canada, ON, Hamilton
Joined May 2011
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Mostly all EDF applications are pushed way beyond the manufactures recommended power settings...take the 1409-2Y//// Max. 1750 watts/75amps...Ya OK!!! I'm pushing 3000watts through it and 90amps..If were talking warranty,that's different but nobody I know follows these recommendations from the supplier.
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Old Apr 06, 2012, 07:40 PM
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Motor

While, I don't really want to destroy, that's why I'm asking how everyone is using motors that are not rated for the high voltage/amps and getting by with it.
Yes I understand they are taking a chance on destroying theirs.
I would just like to get some input, I know they have been given a good rating.
My warranty is long since expired
Thanks
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Old Apr 06, 2012, 07:59 PM
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USA, FL, Lakeland
Joined Jan 2010
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Joe it's watt's so to say. Watts are what a motor operates on.
Really, really layman's explanation, but say a motor is rated at 400 watts.

It doesn't care how you do it, 40 volts @ 10 amps, or 10 volts @ 40 amps. Both are 400 watts.
But on the other hand, watts is heat. As long as you can cool the motor you can fudge on watts.

I ran my Strykers on Mega motors rated at 23 amps, and most of the time I was running em over 50 amps. All day long, and NEVER had an electrical failure. Those motors hung out in the 100+ mph breeze so they got great cooling. Same set up stuck in say a glider, would have been toast in a minute.
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Old Apr 06, 2012, 08:01 PM
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ARC Motor

Quote:
Originally Posted by Extreme_RC View Post
The 2847 will take 50-60 amps if its well cooled, in an alloy housing I think it would run on 6s at 55-58 amps with the CS rotor. 5s should be a breeze. of course there are no guarantees on 6s, the user and the situation at the end of the day will dictate how hot things get...
I have the BananaHobbies F-16 that takes a 5 cell pack on it's way, but I was thinking a 6 cell if I could get it in, but maybe I will just stick with 5 cells.
I will be using at least one cooling ring and 2 if possible.
I appreciate your input very much.
Thank You
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Old Apr 06, 2012, 08:09 PM
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ARC Motor

Quote:
Originally Posted by Glacier Girl View Post
Joe it's watt's so to say. Watts are what a motor operates on.
Really, really layman's explanation, but say a motor is rated at 400 watts.

It doesn't care how you do it, 40 volts @ 10 amps, or 10 volts @ 40 amps. Both are 400 watts.
But on the other hand, watts is heat. As long as you can cool the motor you can fudge on watts.

I ran my Strykers on Mega motors rated at 23 amps, and most of the time I was running em over 50 amps. All day long, and NEVER had an electrical failure. Those motors hung out in the 100+ mph breeze so they got great cooling. Same set up stuck in say a glider, would have been toast in a minute.
Hi Glacier Girl :
I always meant to ask you and the other speed racer's about your motors, I just thought they were rated for high amps and higher cell packs, because I know they costed alot from what I read.
So now I know, thanks for clearing that up :=}
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Old Apr 06, 2012, 09:04 PM
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The 380 can motor (HK $18) I posted a little bit back is ideal for 4S and to use in a Meteor - but if you run it at WOT for long periods the Meteors stock 50A ESC, that seems to cope fine at 58A long term anyway, might just get a bit close to its limit.
The 380 will use 62A ongoing (after battery peak drops off to more stabilised).
I would rather have a 70A esc in it for that setup - which is that will go into my F-15. (same size as Meteor pretty much - but less wing area)

If they had a 2100kv version of that motor it would be great for 5S then.

This HK opto esc:
http://www.hobbyking.com/hobbyking/s...0_70A_ESC.html
I expect to fly around at high 50A's area. Which will be 1.3+Kg thrust in the CS10
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Old Apr 06, 2012, 09:27 PM
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I think the real spec (limit) of motors is CURRENT. More current, hotter windings - especially when the current exceeds what the wires can carry properly. The same reason ESC/battery leads or connectors get hot... when they are "force fed" more current than they can carry. Resistance in the wire(s) then turns that excess into heat. Heading towards being a light bulb, LOL. (that is why incandescant light bulbs glow.... super hot due to high current)

To get to that current level you need volts, and the load (fan/rpm).
There is also a voltage limit at some point - part due to what current that would produce anyway (so that is really a current limit).

So how do you know/pick for a setup????
For a given motor and fan, it will run higher and RPM as the voltage goes higher, with current rising too. (we are talking running within a reasonable region of expected use). So say the following:
3S, 11.1v on a 2000kv motor, in a CS10, makes it draw 30A at 20,000rpm
It is a easy load for the motor, and battery, so it will do that easily.
If you went to 4S, 14.8v, and the motor is still well within capabilities then, it will move to say 40A at 26,000rpm, and still easily within its specs.
5S, 18.5v, 34,000rpm.. the load is getting big by then and the current say 50A (for this motor), and say its specs said 45A max.... you are now running it above its specs (but it will do it).
If the motor is struggling with that load, the RPM ill drop below what a more linear theoretical RPM would have been. But I am saying it can do it ok here.
But at 6S, 22.2v, it is trying to get to 42,000rpm area - which it can't as the load now is way too high for it - and the current also rises far greater than linear, so say it is 65A but only 38,000 rpm (instead of the theoretical 42,000).

This is the limit of that motor - which you (or someone else) needs to find to know that. On 6S the tell tale sign is huge Amps increase over 5S, and much hotter, and RPM floundering.
So that particular motor was ok for 5S - though maybe even then over-taxed... if it was running too hot.

Whichever battery level (3S,4S,5S,6S), in that fan, drove the motor to use it listed specs (45A), then that is the true voltage you can use to run at the manufacturers specs for that fan. eg in the above case, 4S... but 5S wasn't too much over and would surely be ok anyway.

I hope that made some sense in how to see what a motor is capable of, and even how to assign a fair enough level of 'safety' to what you drive one to.

Pretty well ignore volts... but measure current and heat as the main criteria (they are created by the volts really).
And Power..... well you can use that number (volts x amps that it runs at) as a rough guide as to whether the physical size of that motor should even be able to do that area, and survive/last.

If you had another fan, of say 2 blades and 64mm, then that above motor on 6S would likely be fine too. Because its load (2 blades and smaller diameter) would make the 22.2v (6S) x 2000kv = 44,000rpm target a "no effort" task for it. And thus its current draw would be low too, say 30A (but not a very useful thrust output either). So Power is now 650w area.... not a lot for these 28mm motor size. (as opposed to driving them to 800 - 1000w like many do).

The above 'generalised factors' are ok to use if you are running within a reasonable range of the motors abilities (eg not way overloaded etc). Things get a lot greyer as you move away from what the motor can easily do. But you will tend to see that easily enough yourself in the results, heat, rpm floundering etc when you do try to drive the motor outside what it can really do.
And volts whilst there are more in depth technical reasons that they do really matter... it is just not so important if you are in the region of what it was designed to do. For eg, not many 28mm will be doing 7S and 8S without issue (more created by current result).
For general use I would assign more importance to the the voltage limit via linking that to the KV and fan/load of the system. Higher KV can't drive a high load to the rpm its theoretical number show it should get to, so then current and heat rise too high. So you can usually roughly predict what the motor will do at each voltage level (3S,4S,5S,6S) and that is what sets the maximum you would use on it.
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Last edited by PeterVRC; Apr 06, 2012 at 09:38 PM.
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Old Apr 06, 2012, 09:54 PM
Extreme CNC Alloy EDF
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Australia
Joined Mar 2006
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Wire is rated at current, insulation is voltage rated (and temp). Most of our quality inrunners will be wound with a polymide coated wire or similar that has a 180 or 200 deg rating, voltage really should not be a concern in our motors as the insulations should be able to handle 25v easily.

What is a concern is the amount of current we are pulling through the windings as the resistance of the wire produces heat based on the amount of current travelling through it.
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