The tale of The Domino and the Magic Blue Smoke

[Cuban8]

42 minutes ago, kc said:

Surely the ESC would get hotter during a training flight often on low throttle than on a full throttle flight?  Doesn't it work harder when on partial throttle than on full throttle?  Switches on and off more often for partial throttle.    Or is my info wrong?

If weight is not an issue then fit a Rx 'nicad' instead of using the BEC output.  Then an ESC failure will not affect Rx controlling the model.   Needs a switch harness and remembering to switch off after flight and recharge nicad of course.

Perhaps an expert in switch mode power supplies could clear that up - as far as I understand it the output transtors (MOSFETS) are best either fully on or fully off and do dissipate power within themselves during switching from full on to full off and chopping up the supply to the motor i.e. part throttle. They switch very quickly through the 'linear region' between states for this very reason and I guess the designers of power supplies or ESCs take this into account when determining max current and switching frequency. 

I've never known an ESC to cook itself in a vintage model that only wafts around on 1/4 throttle for ages on end.

Edited January 15 by Cuban8

[Nigel R]

Generally true C8.

 

Back-EMF increases with rpm (i.e. with more power, for us). Given that the FETs are switching directly on to a coil, this may mean voltage spikes/peaks/noise during switching have different effects at different speeds and loads.

 

Worth noting, our brushless motors are not a switch mode power supply though, and work differently (although both involve fast switching). That said I am far from an expert - this thread could use one...

Edited January 15 by Nigel R