PC fan on 30 volts

[BrianG]

The FETs used in most ESCs I've seen are just a huge array of surface mounted devices (no mounting "tab"). Therefore, they mostly use the PCB traces as a heatsink. Since there are so many FETs, the PCB is nowhere near big enough.

Schulz apparently attaches heatsinks to the sides of the PCB where the traces end.

Other designs seem to have multiple FET PCBs stacked on top of each other with the heatsink on the top layer. Each layer has the PCB above it laying on top of the FETs so the heat transfers to the layer above it (that sounded confusing even to me). BKs and Quark seem to do this. They have to make sure that each PCB firmly touches the FET below it or the heat won't be conducted as effectively.

[Edit]: Personally, each design leaves room for error and some FETs aren't cooled enough. I would like to see a slab of Aluminum between each layer of FETs, maybe machined so there are little raised squares where the actual FET is to prevent shorts. Each slab is then attached to a heatsink on the sides. Each layer gets cooled more or less equally that way. Although, it would be substantially larger, weigh considerably more, and be more expensive...

[Gustav]

I always think the stacked designs look like they must suffer with low surface area:volume ratio,i wonder how much hotter they are in the middle.

[BrianG]

I think the designers rely on the fact that heat tends to travel from a higher concentration to a lesser concentration. The heatsink on top cools the top layer, which then "attracts" the heat from lower levels. I'm sure those lower levels must be hotter, but FETs conduct less the hotter they get, so they are self-regulating in a way. Of course there are limits, which is why some burn up.

IMO, they should add more heatsink area or more FETs. Adding FETs would do two things:
1: Increase current handling (duh :))
2: Decrease total output resistance, which in turn causes less voltage drop on the devices, which then reduces generated heat, and increases efficiency.

[Gustav]

Air goes in the scoop,then it's forced through a sort of letter box,then it narrows again at the end before it hits the esc.Self explainatory really,just look at the pics.I'll test it out,should work pretty good me thinks.:005: