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BrianG · 05.13.2009, 03:20 PM

Why does an ESC run cooler at WOT than at partial throttle? Simple; fewer on/off pulses. To get variable power, the FETs switch on and off. However, a FET does not switch on and off instantly - there is a ramp up and down. This ramping is where the power is lost as heat. When at partial throttle, the ESC sends more of the on/off pulses to limit the average voltage. Think of it this way, if the ESC is 10% of the time "on" and 90% of the time "off", the motor will see an average of 10% of the battery voltage. At WOT, the ESC is sending full battery voltage, so there are no on/off switching cycles (well, not counting the switching between the phases).

I hope that made sense.

FYI, there is no difference between setting the EPA at something less than 100% and not using the full throttle trigger throw. So, you can have the EPA set at 100%, but if you are only using 1/2 the throttle trigger throw, it's the same amount of losses as setting the EPA at 50% and using full trigger throw.

If the setup is too fast, reduce gearing (will increase torque), get a lower kv motor (may increase torque), or reduce battery voltage.

	(#1)
BrianG RC-Monster Admin Offline Posts: 14,609 Join Date: Nov 2005 Location: Des Moines, IA	05.13.2009, 03:20 PM Why does an ESC run cooler at WOT than at partial throttle? Simple; fewer on/off pulses. To get variable power, the FETs switch on and off. However, a FET does not switch on and off instantly - there is a ramp up and down. This ramping is where the power is lost as heat. When at partial throttle, the ESC sends more of the on/off pulses to limit the average voltage. Think of it this way, if the ESC is 10% of the time "on" and 90% of the time "off", the motor will see an average of 10% of the battery voltage. At WOT, the ESC is sending full battery voltage, so there are no on/off switching cycles (well, not counting the switching between the phases). I hope that made sense. FYI, there is no difference between setting the EPA at something less than 100% and not using the full throttle trigger throw. So, you can have the EPA set at 100%, but if you are only using 1/2 the throttle trigger throw, it's the same amount of losses as setting the EPA at 50% and using full trigger throw. If the setup is too fast, reduce gearing (will increase torque), get a lower kv motor (may increase torque), or reduce battery voltage.