Let's start by saying that motor efficiency has very little to do with ESC heat. The only motor spec that might effect ESC efficiency is the inductance value due to the phase angles produced, which can be more difficult to drive.

Assuming an FET goes rail to rail, the only time an FET dissipates power is when there is a voltage drop across the device AND current flow. If the output of the ESC were perfect square waves (0 rise time), then the ESC would be 100% efficient no matter what the motor is doing with that power. At the 0 point of the square wave, there is full voltage across the FET but 0A (0 watts). At the max point of the square wave, there is 0v dropped but there is max current (0 watts). But during the ramp up (the total time it takes to do this is the slew rate), there is voltage dropped AND current flow, which creates the heat. The longer the ramp, the more power loss and more heat. Higher frequencies have more pulses per second and therefore more "ramp up and downs" which can make them an ESC heat up more. However, too low of a switching frequency will cause the motor to not act correctly.

I think you're right about the driving style. Of course, there are a ton of other factors as well.

While you're throwing input around, make sure it doesn't hit anyone. Someone can lose an eye that way! ;)

Yah, i agree! Power switching is a HUGE issue today!

Check out THIS , I don't really know how they do this, but they use 24khz switching. Something called 'Softswing", the switching is inaudible (first for EV inverters), and by far the most efficient EV inverter too, with 97% eff.

Also, (check my signature) they told to wait for their new 'Hybrid Synchronous Motor" to come out for my vehicle. Would you have any idea what it would be? They told me it would have very broad eff. range, and good torque range, just a very good motor all around...?

But yah, the internal resistance is only part of the losses of heat, a small part.

The whole switching thing is a double edged sword. Too low and the motor speed suffers (not to mention erratic behavior). Too high and you have more losses due to having more switching pulses. By the sounds of it, they are actually decreasing the slew rate, which should cause things to heat up more. I'd be very interested to see how they do that! The only way I can see it working is if they use a tracking power supply, which I don't think is feasible/practical at anything close to the frequencies they are talking about.

I have no idea what kind of motor they have in mind. Personally, I think the motors we have now are pretty darn good since they approach 90% efficiency.

Just to clear things up; I'm not an electrical engineer, just someone with perhaps a less-than-healthy interest in this stuff. :)

Thanks, but I think you need to work harder before you can corner me :)

Well, FET dissipates heat during switching when it is in analog mode, defined by rise and fall time plus capacitance and inductance of load. Which means that load (motor) can influence and does on ESC efficiency as well. Well if you integrate over time then you can calculate power loss on ESC, would be difficult to do that over each individual FET. And yes ther are lots of them in parallel, so 10W over n-FET's with 23.4cm^2 (70mmx34mm) heatsink surface area would be great. Old rule of thumb 1cm^2 per 1W good for 50C.

Do not forget to drive those FET's you need some power too, FET's are field driven but speed cost power, current in this case. In addition do not forget about built-in diode and it's temp dependence, I am assuming you know what this diode does in pair with caps, right.

Brian, for motor to be sensitive to rise and fall of FET's switching motor system (motor and inertia of drive train) must have response time in microseconds at list if not nanoseconds. Our motors without load maybe have ms of response time.

For me it looks like Quark 125A controller might have problem with some component on board, based on Leroy's comment about his low temperature runs with 80A. Does anybody have a clear picture of 125A PCB with FET's control part?

Corner you?


When you say response time, do you mean to say a motors inductance? What do you mean when you say a FET in analog mode? A transistor is a digital piece of hardware, it's either ON or OFF. AC Induction motors especially will smooth out a pulse (switching frequency) from an inverter because of inductance; to create a more sine wave looking shape (wave).

We don't really know how much power is dissipated by the Quark, could be 10 watts (average), also, this would be in a MT application we are talking.

So who knows, my guess for efficiency is roughly 96% efficiency. That's my guess? :032: :030:

I think he means slew rate.

The time it takes to activate a FET, and also important, the ripple it brings along in the signal.

'A transistor is a digital piece of hardware'

I don't think you get the basics of a transistor. because a transistor/FET is a analog as possible. that's what's causing the slew-rate. it's not an on/off operated thing. there are million steps in between.

another thing;

if it has got a 10W heat dissipation, and it's 96% efficient, the input power is 240W, a bl controller is more efficient than that.

10 watts, no one said it was definitively 10 watts. The heat dissipation is totally dependent on power usage, does anyone have an EPA for RC MT? :005: :005:

So what is a transistor in half ON then? :032: A millions steps in between?

I missed the 'average' in the 10W part.

Since when is half on considered digital? if ON is close to 0 of internal resistance, and off is close to endless internal resistance, what is digital about that? The slewrate thing explains itself this way.
depending on the speed the signal is put on (and the speed of the transistor/fet) is one of the things that makes the controller more efficient.

perhaps it's not clear to you what this rise delay means;

The speed of a FET/Transistor isn't endless fast. Nor is it's steering signal. (not to mention the polution of the steering signal), this steering signal is obviously is needed to put a fett into full conduction. It simple takes time before the near 0 ohm (full conduction) status is reached. In this time, the FET isn't on it's ideal internal resistance, but the load (motor) stays the same. the fet is at highest efficiency at full conduction. During this 'travel' to full conduction it produces heat (since the internal reistance is getting smaller and smaller reaching full conduction). The speed in which a signal is able to rise, is explained in volts per micro seccond (slew-rate) This rising is done with a steering signal, this steering signal can not be perfect. once the rice took place on a short amount of time, there always is something as a sinus on top of the block-wave, (it's quite impossible to make perfect block-wave) you need the feedback from the signal to correct the errors in the blockwave. (this is the steering signal) not to mention the far from ideal load of a motor (induction) since a controller works on PWM, it's all about different lengths of 'blockwaves'

Now, decide for yourself; if a transistor was digital, would there be a lost? (digital is 0 and 1, and NOTHING in between, since a FET basicly is analog, you have got losses in switching it ON/OFF (1/0)

Hope this explains.

MAybe 'digital' is a tittle much, but it can't really be called analog either though. Everything in this world takes time, that includes transistor switching, so, that does not necessarily make it analog because of this.
You know what I mean?

that's not the point right now; do YOU know what I mean?

ya i know what you mean. That aspect of the FET is somewhat out of our control is it not?


Just thought of this.... how about a Quantum FET?! :005:

A FET utilizing Quantum Mechanical effects such as entanglement (non-locality), superposition! Who knows maybe we will have the perfect FET someday soon, zero switch on time, room-temp super-conducting... :017:

Rene, you are the man!

Zeropointbug, this little bit cost efficiency. And if you spent some time reading about FET's and how it works, then maybe you change your view point on digital and analog. Otherwise it is pointless even talking about any efficiency problems inside ESC...

Hey! Cut that out!

How is it pointless talking about efficiency of an esc? lol

So efficiency doesn't matter to you?

That's not Artur's point zero.

you still see a fet as a digital device, read my post #91, and simple read it entirely. What Artur means is that if you don't change your point of view on digital/analog, he sees no point in discussing the efficiency of a controller with you.

IF you keep seeing a fet/transistor as a digital device (OFF/ON) there is no such thing as losses due to the the constant changing of 0 to 1 to 0 to 1..

just read post #91, it should explain.

Why do you think I THINK that?!

What do I have to do to make it clear to you that I am AWARE of switching/slew rates....

Just because it takes time to switch on, does not make it analog! That's just an illusion.

useless..

clean up these last posts, this was a heatsink thread. I am not finished on it yet, until I get my parts, it's on hold. don't say that...

there is no reason for deleting these posts, there is valuable information in some of them.

w/e, leave them if you want. It's not very clear information.

Well i got the Arctic Silver adhesive in today, and went to my machinist, but he doesn't stock copper... bummer. So i am using aluminum instead, should work great still, might run a few degrees warmer though.

I'll post some more pics when I get the piece cut, and pasted on.

Here is the results. Let me tell you, it was a tight fit! I should have lapped down the thickness of the alum. pad a little bit, the case ends were tight fit to go it, and the programming button was tight into the button pad (you might be able to see it in the pic. But i did a quick test running it on the table, the Quark gets a little very quickly unlike before where it took a while.... then I popped it onto the big heatsink and instantly was chilled back down to room temp.

I have a feeling this setup will work beautifully! ;)

Stay tuned, I am going to tap the copper heatspreader on the heatsink and use 3mm screws with the CF plate to secure the Quark down with pressure.

I've got my controller taken apart at work atm, cut a copper shim, but it's about 2.5mm thick, and sits at the same level as the capacitors. I planned on using that, and then just dremeling out a small pocket in the case for the caps to clear. but, was hoping that I'd be able to use regular thermal paste, instead of adhesive.. so I've got another shim about 1mm thick, so i'm guessing it's about the same height as your shim zero. I see that it's a tight fit.. do you think there's enough pressure to keep your shim in place, if it was non-adhesive thermal paste?

You must, I repeat, you MUST use adhesive on this. Paste will not do anything, it's just a grease really. Try and find some Alumina, or Silver adhesive, if you can, use Alumina, as it's better for being in with electronics. I used Arctic Silver adhesive though, worked great, took about 1/2 hour to dry until it was stuck on for good. I made my alum slab 42mmx29mmx3.175mm(1/8").

However, I should made it 27mm wide instead of 29mm, as I had to perfectly align it with the board, even then, it was slightly crooked, and was tight fitting when I adhered it to the case.

Also, my board didn't seem to be flat , because the two ends were off the slab by a hair, nothing the adhesive couldn't take care of.

One more thing, the button was pushing in the top 'button cover' pretty good, although it didn't activate the button though. So I took the cover off again and took a exacto knife and scraped .5mm off of it, as there was a nipple on it. Now the button cover sits down the way it was before.



AGAIN, you MUST use adhesive for this mod, otherwise there is no point in doing it. Paste simply is simply not sticky, it's a grease, and the board will just flop around in the case.

not exactly true. that's why i was asking how much pressure there is. I test mac upgrade processors, and we basically have the heatsink, thermal paste, shim, thermal paste, cpu die. the pcb is screwed to the heatsink at the 4 corners, but there's more than enough pressure on the die to keep everything in place, even in hard impacts..

Let's just say there is no pressure in the case of the Quark, because there is none, If the board is loose, it's loose. Nothing is holding it in place but the pad, and nothing but the pad.

The problem with just using paste is that the board can move around inside the case a little. And with thermal grease (of any kind), movement of the mating surfaces will reduce its effectiveness. In your computer example, you state that the sinks are also bolted - that keeps the mating surfaces consistent. And just think what would happen if dirt gets in there and starts mixing with the grease as it moves around! Ugg. I agree with ZPB on this one - thermal epoxy is all but required.