9 replies to this topic

[dalek]

I'm posting the following as a heads-up to anyone who has heard that it's a good idea to cover an ESC (which actually probably is but not the way I did it).

Last night the X89 ESC and KC 4500Kv motor, in my GTP brushless car, failed.

I had a piece of Gorilla tape stuck on top of the ESC, to keep debris from getting on it, and for now I'm assuming the tape caused two of the chips on the ESC to overheat to the point of failure which in turn caused the motor to overheat (so badly that a winding burnt in two).

The two chips on the ESC that failed got hot enough to melt the Gorilla tape that was stuck on the top of them.

[mreibman]

I actually have 2-sided heat-conductive tape used to attach heatsinks. Perhaps that might be a better method. And despite any weight, a heatsink would probably be a good idea.

[Tim Wood]

I thought that Brushless Motors ran cooler. And you could run multiple races with them. Why would you need a heatsink. 

[Tim Neja]

I thought that Brushless Motors ran cooler. And you could run multiple races with them. Why would you need a heatsink. 

 

Some are severely overgearing them and it's causing heat build up in both the motor and ESC!! I've got no larger than an 8 tooth 64p pinion on ALL of mine from 3000KV to 12000KV and they run great!  Most are geared 7/39.

[Bill Breck]

The thermal paste that computer builders use might help out if you use a heatsink.

 

 

 

[jimht]

I thought that brushless motors ran cooler. And you could run multiple races with them. Why would you need a heatsink. 

 

Keeping the ecom components from getting hot enough to desolder is the issue, not motor heat.

 

A heatsink for the ecom is better than not.

 

I use .5mm aluminum sheet attached with .3mm heatsink tape.

[Bill Seitz]

Increasing the load on any motor increases how hot the motor gets, and there's nothing really fundamentally different about brushless and brushed motors to make a difference in how hot they get. Brushless adds the commutating electronics, and that can also get hot. If the ESC/ECom has current limiting, then this may prevent both motor and electronics from overheating and blowing, but I suspect the electronics is designed with expectation of some amount of heat dissipation. A popular drone ESC requires an airflow level that I don't think is possible with slot cars, and my casual observance of slot car electronics didn't reveal what level of cooling was expected. Thermally conductive tape is designed to pass heat while providing electrical isolation, but does nothing to increase dissipation. It's better than other types of tape, but still has some thermal resistance, so the electronics will run hotter under even the thermal tape. The best alternative is to provide some additional heat sink with other a commercially available small heat sink or a fabricated one as Jim Honeycutt describes attached with a thermally conductive adhesive.

 

Most electronic devices are rated for a max temperature of 150 C. which may seem like a lot. However, there's a temperature vs. power (voltage/current) safe operating area, and the higher the temperature, the lower the safe output current. Depending on the device, the output current near 150 C. can be a small fraction of the max. current rating which is with the device maintained at 25 C. There's no power electronic device that can dissipate enough heat on its own without the help of some heat sink. In the case of SMD devices used on a ECom, they depend on square inches of PCB foil or an auxiliary cooling device. I was reviewing data for a power FET recently, and it required 6 sq. in. of foil to cool it. I haven't seen an Ecom or ESC with 6 square inches x 3 (there are usually 3 FET's) of exposed foil area, so you get the picture. Unfortunately, the heat dissipating surface of the SMD chips is on the side soldered to the PWB. The exposed plastic package is a poor thermal interface for attaching a heat sink, although anything will be better than nothing.

 

In my electronics experience, thermal failures are often the cause of electronics failures, and the thermal requirements are frequently underestimated and poorly considered. It never hurts electronic reliability to improve heat dissipation.

[Ramcatlarry]

Cooling ducts can be made from a simple straw to direct air to the part that needs cooling.  Did that many years ago trying to help 16Ds from melting down from the bad battery chargers in use at the time.

 

FYI:  Tesla EVs use a water jacket and radiator for their ESC system

[Mr. M]

Thermal tape with a chunk of Al may make all the difference when placed on the ICs. Something simple like 0.032 Al plate the size of the ESC.

[team burrito]

it sounds like it was overgeared & the gorilla tape smothered the electronics.