Quick question

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bitternboy
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Quick question

Post by bitternboy »

How long do you think a 20A brushless ESC would last at 22.2A?
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Re: Quick question

Post by razerdave »

Are you going to be pulling 22.2A on a continuous basis ? If yes, it won't last 2 seconds. The ratings on most speedos is the continuous rating. It may take over that as a burst current, but not for a sustained period.
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BeligerAnt
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Re: Quick question

Post by BeligerAnt »

If that is the stall current of the motor then you should be OK. Most controllers will handle an over-current for a short while. 10% over is quite modest.
If it's the normal running current you are expecting then you do need a bigger controller. I'd suggest a 30A controller for a 20A continuous load so you don't have to worry about keeping the controller cool.
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bitternboy
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Re: Quick question

Post by bitternboy »

Ok, that sounds sensible. 22.2A is the continuous draw at the battery voltage but I was planning to run the motor at half throttle. Doubtless it would be run at full throttle by accident at some point so a 30A sounds like a good idea. Do you think buying 50% extra is a good policy to stick to in terms of brushless ESCs?
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Shakey
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Re: Quick question

Post by Shakey »

Due to the way ESC's switch running at under full throttle will produce more heat than full throttle as the H bridges are constantly switching creating resistance rather than being a fully open switch.

Interestingly running a little under full throttle also has a higher current draw than full throttle as well as higher heat production.
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BeligerAnt
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Re: Quick question

Post by BeligerAnt »

Not quite true Alex!
Even at full throttle the H-bridges are switching in order to provide commutation. The switching losses are thus (more or less) constant, but the conduction losses increase with throttle position (duty cycle).
An H-bridge will have lower losses at 100% duty cycle, but this only happens with brushed motors where the transistors/FETs are not switching.
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Shakey
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Re: Quick question

Post by Shakey »

Woops my bad, I read it wronged and was thinking in brushed mode :P
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