Speed limit on GTB
05-31-2007, 05:52 AM
#16
Originally Posted by B-day
ESC at 80% throttle will convert the rest 20% to heat???? The biggest BS I have ever seen. 
05-31-2007, 11:18 AM
#18
Best way to know, ask Charlie from Novak, cause I think you can turn your EPA down as much as you want and your ESC will not get any hotter.
With brushed motors, they send pulses to the FET's, less pulses or smaller active on for the FET causes the motor to go slower (average vltage is lower). Dunno about brushless though (School has been too long ago)
If the ESC is burning 20% heat when you're at 80% throttle -> with this way of thinking you would SHORT the battery when you dont give any throttle at all....
I say, just turn down the epa (if I do am wrong, it will thermal without leaving damage)
With brushed motors, they send pulses to the FET's, less pulses or smaller active on for the FET causes the motor to go slower (average vltage is lower). Dunno about brushless though (School has been too long ago)
If the ESC is burning 20% heat when you're at 80% throttle -> with this way of thinking you would SHORT the battery when you dont give any throttle at all....
I say, just turn down the epa (if I do am wrong, it will thermal without leaving damage)
06-01-2007, 07:26 PM
#20
Originally Posted by quick5pnt0
How about just giving it less throttle? 
06-02-2007, 02:09 AM
#21
dang, charlie blocks pms.. charlie... can we get an answer here pls! :P
06-03-2007, 11:30 AM
#22
Originally Posted by dorick
dang, charlie blocks pms.. charlie... can we get an answer here pls! :P
during the work week....
06-03-2007, 04:43 PM
#23
At 100% throttle, the FETs in your speed control are full on, not pulsing. That's the condition of least resistance. Remember, resistance = heat.
At less than full throttle (either holding less trigger, or using less EPA) the FETs are pulsing, and when they're switching from off to on that's when they're heating up... so if you've got them constantly switching, they will run hotter than if they are fully on.
Disclaimer: I'm not an electronics expert, but that's the explanation I got as I understood it. Someone more knowledgeable may want to chime in here and correct me if I'm mistaken.
At less than full throttle (either holding less trigger, or using less EPA) the FETs are pulsing, and when they're switching from off to on that's when they're heating up... so if you've got them constantly switching, they will run hotter than if they are fully on.
Disclaimer: I'm not an electronics expert, but that's the explanation I got as I understood it. Someone more knowledgeable may want to chime in here and correct me if I'm mistaken.
06-03-2007, 05:10 PM
#24
In a brushed setup, that's closer to the deal. In a brushless ESC, they're always cycling on and off. That's how the commutation (phase selection and charging) is done in a brushless motor. In a brushed motor, the rotor turns past the brushes and the brushes contact one segment of the com, then the next...brushless phases are energized in sequence by the FETs.
There's a BUNCH of very useful information directly from Novak in the "speed spectrum ESC" thread (sic). They go into some detail as to where the heat in a brushless ESC actually comes from...it's the period in between "off" and "on"...that period is shorter (much shorter) in the 2.4Ghz ESC, so it runs cooler.
I'm not convinced at all that reducing the EPA is different from just using less throttle. It's been my experience that they do seem to run a little hotter (under load) at part-throttle, but that shouldn't be any different than lowering the EPA.
There's a BUNCH of very useful information directly from Novak in the "speed spectrum ESC" thread (sic). They go into some detail as to where the heat in a brushless ESC actually comes from...it's the period in between "off" and "on"...that period is shorter (much shorter) in the 2.4Ghz ESC, so it runs cooler.
I'm not convinced at all that reducing the EPA is different from just using less throttle. It's been my experience that they do seem to run a little hotter (under load) at part-throttle, but that shouldn't be any different than lowering the EPA.
Originally Posted by Trips
At 100% throttle, the FETs in your speed control are full on, not pulsing. That's the condition of least resistance. Remember, resistance = heat.
At less than full throttle (either holding less trigger, or using less EPA) the FETs are pulsing, and when they're switching from off to on that's when they're heating up... so if you've got them constantly switching, they will run hotter than if they are fully on.
Disclaimer: I'm not an electronics expert, but that's the explanation I got as I understood it. Someone more knowledgeable may want to chime in here and correct me if I'm mistaken.
At less than full throttle (either holding less trigger, or using less EPA) the FETs are pulsing, and when they're switching from off to on that's when they're heating up... so if you've got them constantly switching, they will run hotter than if they are fully on.
Disclaimer: I'm not an electronics expert, but that's the explanation I got as I understood it. Someone more knowledgeable may want to chime in here and correct me if I'm mistaken.
06-03-2007, 09:11 PM
#25
also the flip side of fets is, fully on = max curerent flow all the time = more heat
pulsing 1/2 on or 3/4 on (ie limitting epa) = current flow only 1/2 the time= less heat.
i very much doubt limitting the epa of throtle will heat up the esc or motor any more
i am a Electronics Tech.....
pulsing 1/2 on or 3/4 on (ie limitting epa) = current flow only 1/2 the time= less heat.
i very much doubt limitting the epa of throtle will heat up the esc or motor any more
i am a Electronics Tech.....
06-03-2007, 10:21 PM
#26
Originally Posted by LOSI123
also the flip side of fets is, fully on = max curerent flow all the time = more heat
pulsing 1/2 on or 3/4 on (ie limitting epa) = current flow only 1/2 the time= less heat.
i very much doubt limitting the epa of throtle will heat up the esc or motor any more
i am a Electronics Tech.....
pulsing 1/2 on or 3/4 on (ie limitting epa) = current flow only 1/2 the time= less heat.
i very much doubt limitting the epa of throtle will heat up the esc or motor any more
i am a Electronics Tech.....
They don't have much resistance when they're on, so that's not when they make heat. It's when they're "between" on and off that they make heat.
Seriously, check out that thread on the new GTB I was talking about above...it pretty much lays it all out...right from Bob Novak and Adnan Khan themselves.
Here you go...
http://rctech.net/forum/showpost.php...9&postcount=28
Last edited by Turbo Joe; 06-03-2007 at 10:41 PM.
06-04-2007, 02:52 AM
#28
Originally Posted by LOSI123
just pointing out some simple theory, there was some one that tested it out and they said there esc runed cooler so,
i will read everything then do my own testing as well as you cant always beleive every thing you read.
i will read everything then do my own testing as well as you cant always beleive every thing you read.
Uhhhh...ok...if you don't believe the dude who MADE the GTB about how the thing works...then...well...I don't know really what anyone can say to you.
You have fun testing now.
06-04-2007, 03:09 AM
#29
1st. I will admit, i am most probably wrong,
but there have been some saying they did limit the epa and there esc ran cooler so unless they are totaly dumb, then maybe it should at least be tested on bench conditions.
(not being sarcastic here, either)
but maybe they said that so that pepole buy all the diff motors?
just saying it might be worth a test for someone that has the spare time.
but there have been some saying they did limit the epa and there esc ran cooler so unless they are totaly dumb, then maybe it should at least be tested on bench conditions.
(not being sarcastic here, either)
but maybe they said that so that pepole buy all the diff motors?
just saying it might be worth a test for someone that has the spare time.
