Motor Controllers

[aldaeron]

Originally Posted by electroken

Part of my own evaluation of the SPARK was having a look inside. While much of the case is plastic, the SPARK label in the center is covering a heavy c-channel shaped slug of aluminum with heat transfer pads to encourage cooling of the 4 MOSFETs and 3 electrolytic capacitors under it. My gut feel (with nothing but experience to back it up) tells me this device will survive a 2-minute pushing match just fine.

The footprint is close, but not identical to that of the Talon SR.

I don't have one to look at, but what I said is still true based on what you are describing. The internal aluminum heatsink will draw heat away from the components, which is helpful, but you need to look at the path the heat takes after that. In the case of the REV spark, this means conduction through a plastic case of some thickness then out to whatever the controller is mounted to. Compared with the aluminum body of the Victor/Talon that does not have this additional layer of restriction. Keep in mind that plastics have Thermal Conductivity of <1 W/mK compared with Aluminum that has Thermal Conductivity of 200 W/mK. While it is true the footprint sizes are different, my guess is that this will not have a large effect, especially if there is no thermal paste/pad between the aluminum heatsink and the plastic case.

For effective thermal management I like mounting the controllers to a hefty aluminum frame member or sheet metal belly pan of decent thickness. Wood or plastic or heavily pocketed aluminum belly pans limit the ability to conduct heat away from the mounting location.

Perhaps the REV will be fine for most situations, but what I said is still true - the Victor/Talon will be better because there is no plastic in the thermal conduction path. I believe REV is planning to release test data soon. Hopefully they will instrument down to the package level or heatsink right next to the MOSFET case and will provide ThetaJC values for the devices. The junction temperature is what is key for long term performance and reliability.

It really depends on current draw of the motors and efficiency of the controllers during matches as to how much heat you really need to dump. But keep in mind that in a Best-of-3 Finals match that you do not have as much time to cool off as during a normal match. It can be a problem.

TL DR: REV may be fine, but Victor/Talon will be better for dumping heat.

-matto-

[electroken]

I'm not questioning any thing you've said, and I fully understand that the slug of aluminum only buys time, and in the end the vast majority of heat must be radiated to the environment through the 1.5-ish square inches of aluminum exposed to the air.

Having spent some time within the Talon SR and the Spark, it is my opinion that teams familiar with the Talon SR will see similar results from the Spark.