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I do not understand why ithere is a KV limit
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coptor View Drop Down
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Posts: 860 		  Quote coptor Quote  Post ReplyReply Direct Link To This Post Topic: I do not understand why ithere is a KV limit
    Posted: 27/Jun/2012 at 11:17am
on this esc?

http://www.hobbyking.com/hobbyking/store/__6461__Hobbyking_SS_Series_35_40A_ESC.html



I thought ESC's are limited based on amps drawn by the motor.

Why is there a KV issue now ?

If this is true for this suppo based esc, isn't it true for the rest of them below 40 amps suppo esc too ?


That means these esc can never be used for EDF or heli motors.

Are they so cheap and crappy they can't handle high KV motors that draw less than the ESC's rated amps ?
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flarssen View Drop Down
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Posts: 1248 		  Quote flarssen Quote  Post ReplyReply Direct Link To This Post Posted: 27/Jun/2012 at 2:17pm
ESC's have a limit for how fast it can commutate the motor (RPM). Usually this is given in RPM for a 2 pole motor, like 210.000 RPM. For a 12 pole motor, this should be divided by 6, so 35.000 RPM would be max in this example. I have fried a cheap ESC when running a self wound high Kv/high pole count motor without any load at all. When max RPM was exceeded, the ESC went nuts and opened FET's in the wrong fashion, thereby shorting the battery. Same motor worked great using a Castle Creation ESC.
I could be wrong, but I believe this is what they are trying to say. What they are missing is the fact that pole count counts too , and so does the actual voltage.
When they say max 2000kv, a 4000kv 2 pole inrunner motor would probably be no problem, but don't take my word for it    

Fred

Edited by flarssen - 27/Jun/2012 at 2:19pm
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coptor View Drop Down
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Posts: 860 		  Quote coptor Quote  Post ReplyReply Direct Link To This Post Posted: 02/Jul/2012 at 11:18am
Originally posted by flarssen

ESC's have a limit for how fast it can commutate the motor (RPM). Usually this is given in RPM for a 2 pole motor, like 210.000 RPM. For a 12 pole motor, this should be divided by 6, so 35.000 RPM would be max in this example. I have fried a cheap ESC when running a self wound high Kv/high pole count motor without any load at all. When max RPM was exceeded, the ESC went nuts and opened FET's in the wrong fashion, thereby shorting the battery. Same motor worked great using a Castle Creation ESC.
I could be wrong, but I believe this is what they are trying to say. What they are missing is the fact that pole count counts too , and so does the actual voltage.
When they say max 2000kv, a 4000kv 2 pole inrunner motor would probably be no problem, but don't take my word for it    

Fred




That explained why these supersimple escs are not so good for EDF motors.. hah!
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Posts: 2798 		  Quote airwave Quote  Post ReplyReply Direct Link To This Post Posted: 02/Jul/2012 at 11:45am
It is based on the FET speed,ss don't have the best reted FET's.if it fails to cycle right you end up with the battery shorting out then they let the smoke out.
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