RC-Monster Forums - View Single Post - Team Tekin R1 Pro brushless speed controller

BrianG · 01.18.2007, 10:59 PM

It's not so much the high voltage or the current that causes the heat on the ESC, it's the time that there is a voltage drop on the FETs when current passes though it that causes the heat. And this happens mostly during the very short time it takes for the FET to switch on and off.

If the FET had VERY fast switching times, very low "on" resistance, with almost no rise time delay, and enough of them were in parallel (to further reduce the "on" resistance), it is possible I suppose to run an ESC without a heatsink.

For comparison: The MM specifies an "on" resistance of 0.0003 ohms. That's 0.03v dropped on it at 100A, which is 3W dissipation. Since that is kinda low to produce the heat we see on these ESCs especially since we never draw 100A continuously, I would say that the FETs have some type of slope when they switch on and off, which would account for the extra heat.

The R1 pro specifies the on resistance of 0.00005 ohms. That's 0.005v dropped on the ESC at 100A, which is 0.5 watts!

Based on the fact that the "on" resistance is 6 times lower than the MM alone, it should maybe run a little warm without the heatsink.

	(#10)
BrianG RC-Monster Admin Offline Posts: 14,609 Join Date: Nov 2005 Location: Des Moines, IA	01.18.2007, 10:59 PM It's not so much the high voltage or the current that causes the heat on the ESC, it's the time that there is a voltage drop on the FETs when current passes though it that causes the heat. And this happens mostly during the very short time it takes for the FET to switch on and off. If the FET had VERY fast switching times, very low "on" resistance, with almost no rise time delay, and enough of them were in parallel (to further reduce the "on" resistance), it is possible I suppose to run an ESC without a heatsink. For comparison: The MM specifies an "on" resistance of 0.0003 ohms. That's 0.03v dropped on it at 100A, which is 3W dissipation. Since that is kinda low to produce the heat we see on these ESCs especially since we never draw 100A continuously, I would say that the FETs have some type of slope when they switch on and off, which would account for the extra heat. The R1 pro specifies the on resistance of 0.00005 ohms. That's 0.005v dropped on the ESC at 100A, which is 0.5 watts! Based on the fact that the "on" resistance is 6 times lower than the MM alone, it should maybe run a little warm without the heatsink.