You tend to get what you pay for!

This is a cheap 20A ESC. Although it works as well as any other just look at the imprint the MOSFETS have left on the heat sink conductive layer. :ohmy:

Clearly two of the MOSFETS are hardly touching the conductive layer at all so would certainly be less well cooled than the others.
I suspect even running at half the rated current there would be a real risk of it failing.
Of course there is absolutely no way of knowing of this defect with taking it apart.

We shall see if a different heat sink with a new 'softer' conductive layer is any better.

Used one of those myself Q. It lasted all of 1 min. Taxied out and it packed up.

You are dead right, you DO get what you pay for these days, buy cheap, look out !!!

Garry

ever seeking to improve my knowledge of all things model flying, and wanting to ask in a techy way, wassamoffset? and where do they live on that board full of squiggly bits

They are the square bits , 6 of them Alan, but what they do is beyond me. Over to you Q


Garry

The acronym stands for - Metal Oxide Silicon (or Semiconducting) Field Effect Transistor - in other words an electrical switch with very low loss and very fast action (and no moving parts!)
Metal Oxide is also known as rust! (also the stuff that recording tapes are made of, on a plastic ribbon backing)

Alan
The MOSFETS are the clever bits (usually 6, 2 for each motor wire) that do the high speed power current switching required for the brushless motor.
If say you are running a 500W set up and they are 95% efficient then 25W (soldering iron power) has to be removed from the top of them and most solid state electronic devices don't like going much above 100 degrees C so they need positive cooling.
The bigger ESC used in model cars have built in cooling fans and in boats they are water cooled.

Hi,
Just a couple of points here, MOSFET's used in the modern ESC's act just like switches, they are either on or off, there is no intermediate state therefore power cannot be dissipated across a short circuit (MOSFET on state) nor can power be dissipated across an open circuit (MOSFET off state). The heat dissipated in a MOSFET comes from the slight inefficiency of the MOSFET where the higher the operating characteristic of a MOSFET the less heat will be dissipated for a given current say 20 amps. MOSFET's may be placed in parallel to increase the current capabilities of the design therefore less heat is dissipated. Looking at say a cheap 20 amp ESC there may only be 6 MOSFET's to control the motor (3 sets of 2 in parallel) to drive the 3 phase motor, in a more expensive 20 amp ESC there may be as many as 12 MOSFET's to control the motor (3 sets of 4 in parallel) to drive the 3 phase motor thus less heat dissipation.
Hope this was not too difficult to follow. Note: ESC's rated at 40 amps or more generally have a 5-6 volts switched BEC whereas anything less than 40 amps rating will typically have a linear BEC i.e. if you require 5 volts at 2 amps from a 3S battery this would result in 14 watts of power dissipated in the ESC nominal battery volts equals 12volts therefore (12-5)x2 = 14 watts. Voltage x Current = Watts (Ohm's Law), switched BEC's are more efficient.

Regards,
sydc.

switched BEC's are more efficient.
And generally more electronically noisy. (Put a switch-mode psu near a sensitive receiver!) :evil: (both turned on, of course!)