ESC Heat Issues

[Doby]

There have been some comments made that if a brushless ESC is not run full out all the time, then heat could be an issue with the controller.

Last weekend, I performed a few experiments. Nothing overly scientific mind you.

Boat #1, 33" DF, Neu 1521, 4S2P, 100 Amp Pulso Speedo.
Boat #2, TS-2, Black Jack Motor, 4S, X-Power 100 Amp Speedo.
Boat #3, Stock SV-27 on 4S

For each boat I brought 3 sets of fairly identical LiPos.

Each boat was run 3 times in the following order. DF 33, TS-2 and then the SV. This allowed for more than ample time for each boat to cool down to ambient before it was run again. After each run I measured the temps of the speed controller.

1st run was flat out to simulate as close as possible race speeds for 4 laps
2nd run was trying to run each at about 1/2 speed speed for 4 laps
3rd run was "bashing" speeds, on plane, off plain, full speed, half speed, ,,, just plain goofing around for 4 laps

Again, I will state, nothing too scientific.


Results;

There was only about a few degrees difference between the temperature readings on all three different controllers after each of the three different runs.

The Pulso was around the 95- 100 mark.
The X Power was around the 90-95 mark.
The SV was around the 95-100 mark.

So, can we draw any conclusions from this, probably not, but the numbers speak for themselves.

So,,,,,in my not so scientific study, I can conclude that it makes no difference if you run flat out or not.

Just thought I would post this as an "FYI".

Your results may (and probably will) vary.

[ED66677]

I hope I understand correctly what you're saying Doby...
you demonstrated on 3 different boats with 3 different ESC's that no matter if you run WOT or half throttle the temp remains the same.
That is interresting as most of what I did read stated that BL systems run cooler WOT than half throttle, but how do they do in the industry with BL systems? no heat issue!!!
Here's what I suspect, BL "over"heat when running unloaded, that's for sure, but what is the difference between WOT and half?
When running WOT the ESC has to dissipate a certain power given by the voltage, the ESC's internal resistance and of course the amps running through it, half throttle, the ESC "sends" less volts to the motor so less amp are drawn, but the internal resistance remains the same, the dissipated power is then less than when running WOT, assuming your ESC's are water cooled, at half throttle the flow of water is less than when running WOT so heat exchange is not as efficient (I might be wrong), this would explain the same temp you measured!!! WOT more heat but better heat dissipation half throttle less heat but less dissipation!

[Doby]

[QUOTE=ED66677;83757]I hope I understand correctly what you're saying Doby...
you demonstrated on 3 different boats with 3 different ESC's that no matter if you run WOT or half throttle the temp remains the same.
QUOTE]

Yup, give or take a few degrees.

[Flying Scotsman]

Very interesting John. What props were used?

Douggie

[Doby]

Douggie;

The props shouldn't matter as everything remained the same for each of the runs. I'll let you know what props are on later tonight when I get home.

Also, it was around 7 deg C that day, brrrrrrrrrrrrr.

[Ub Hauled]

It's about 6deg C here right now, and windy... not going boating today...

What happened to California?!?!

[ReddyWatts]

Thanks for the info. Those motors are 4 and 6 pole. Try it on a 2 pole and let us know the results.

[detox]

Try a test using Castle's Hydra 120 or 240 esc. Then compair that to the ETTI 150 esc.

[Doby]

Try a test using Castle's Hydra 120 or 240 esc. Then compair that to the ETTI 150 esc.

Sure, send me the controllers.

[Flyguy55]

Thanks Doby for doing the test and sharing . Its useful information .

[Steven Vaccaro]

What I get out of this is that I'm in awe that the x-power and pulso are still alive! Good work.

[ReddyWatts]

Here is an explanation of running an ESC at half throttle from Castles site, given to us from Fast Guy.
"A speed controller controls power to the motor by turning full throttle current on and off really fast, 11 to 13 thousand times per second (Pulse Width Modulation or PWM). The percentage of each on/off pulse that is off compared to the part that is on determines how much power the motor sees. I.E. With a pulse that is 50% off and 50% on the motor will see 50% power*. Because each on pulse is 100% of full throttle current, a system set to pull 20 amps at full throttle through a Phoenix 10 will not last if you are throttled back to the point where you only see 10 amps on a wattmeter. The ESC in this case is still switching 20 amps, which it can’t do for long. Actually it is worse than the simple example above. Because an electric motor will always to try to pull as much power as is available to get to its rpm (volts times Kv), when you are running the motor below its Kv speed by switching power on an off, each on pulse will actually be way over the full throttle amp draw. That is why ESCs work harder at partial throttle than full throttle and why we underrate our ESCs. We underrate not so they can handle more current than their rating at full throttle, but so they can handle extended partial throttle operation with no problems."

[ED66677]

that's a good explanation ReddyWatts but that does not explain why Doby measured equal temps???

A speed controller controls power to the motor by turning full throttle current on and off really fast

faster at half throttle than WOT, that's for sure!

when you are running the motor below its Kv speed by switching power on an off, each on pulse will actually be way over the full throttle amp draw

more amp spikes because more pulses?
Also as far as I know BL systems on rc planes or heli don't overheat, My T-rex450 heli is running at 70 or 80% throttle most of the time, as I'm learning and mainly hovering, and I never noticed ESC's overheating!

[ReddyWatts]

That is what makes this interesting. Does the controller have to running closer to max amps to see the 1/2 throttle over heating?

[ED66677]

I talked about it with a friend, he is modeler as well and I used to tow his large gliders in the past, this guy is really good in electronic engineering and does some avanced circuitery for his models, he said (I'm not taking this as absolute reference though but he confirmed what I suspected/knew ) that :

- WOT the MosFet's have to switch on and off according to the motor rpm, if the motor runs at 30000 rpm then MosFet's switch the ESC input voltage at 500Hz

- In intermediary phases (not WOT), let's say 15000 at half throttle, MosFet's have to switch the input voltage at 250Hz, but to get the 15000rpm only half of the input voltage is required (according to motor KV) to get half of the input voltage the MosFet's have to switch on and off to another frequency witch is the PWM, the one that sometimes can be modified on ESC's, 8, 16 or 32Khz, so in the case the PWM is at 32Khz at half throttle the MosFet's have to switch at 250x32000=8000Khz! that's hudge! and the issue is that MosFet's have a bad efficiency during the switching/triggering phase, meaning that they do heat a lot more when triggering (between off and on state) than when triggered (on state).

Now back to Doby's experiment, I suspected a difference in the cooling efficiency at half or WOT, but that was assuming the cooling is better at WOT than half, but that's probably not thrue , if the water flows fast through the cooling system, the heat exchange is less than if the water runs slower (in a certain range or limit), so WOT there's less heat to dissipate (according to the above statement) but not as efficient cooling giving the same temp than when more heat has to be disspated but when the cooling is more efficient!

The only way to confirm the above would be to measure water temp on the inlet/outlet, I'm sure we would be very surprised!... and eventually to perform a short test without cooling to see ESC's temp in both case half and WOT!

Doby can you do another bunch of test after you changed the PWM on each ESC?

I like that one! now I and see what others think!

EDIT: we also have to take to account that at half throttle the power output might not be half of the power at WOT!!! that also has a large impact on the heat to be dissipated!