@ Alec_t: How's this for simpler?
I like it, good theory. My theory was more simple... but yours more likely has the better benefit of actually being correct. (which tends to help from time to time.
)
@KISS: I believe Joe said that there was goopy stuff and epoxy. [snip] The goopy stuff probably doesn't conduct heat very well and neither does Fiberglass.
If not for Joe's latest comment, I would have said it was possible. It's true enough that most polymers are terrible conductors of heat. However solids, and even "goopy stuff" conduct heat FAR better by volume/distance than trapped gasses do in reality. So with the huge gap of solder's melting temp (~185°C) and waters boiling point (100°C), *AND* less than an inch (guessing) of epoxy between the hot part and water... I still think the
"paper cup effect" would start to take place before any solder would melt. And even if it did get some what molten... How would it then short out? Being liquid and hot doesn't necessarily stop it from being at least slowed down by the epoxy/goopy stuff. Unless there was already a void there of course. (Which I suppose is totally possible given the location of the short.)
To farther put nails in that coffin though, we can examine the flip side of the coin. If we assume the epoxy did in fact act as a realistic insulator. And that it got hot enough to boil out of the way and allow a short to form. You would also expect it to have caused a crack and/or explode out that section (As I see in blown transistors a lot). Or it should have at least shown some signs of getting supper hot IMHO.
(All of the above presumes that the short
that we know exists was the cause of the failure. However the existence of the short does not necessarily exclude the possibility of transistor internal meltdown. Though it does tend to lean away from it quite a lot.)
Salty, You don't need to answer in all honestly but just for the sake of argument; did you happen to notice anything out of the norm before you took a torch to the epoxy? Any cracking or bubbles? Or do you distinctly remember that there was nothing at all wrong with the epoxy's surface, IE it *WAS* glossy and smooth. It really doesn't matter though because....
This Novel is getting long.
I agree, I would have been fine with not doing the autopsy on the pump and just stick to the driver changes honestly. It's only created needless speculation. Truthfully, I never figured it was going to tell us anything we can use that we (I ?) didn't already expect either. It's a brushless motor, so we should current limit the driver as best we can and protect it from transient voltage spikes... I feel like I said this all before... but I'm not sure and I'm far to lazy to reread the whole novel.
:sigh: Wish there was something I could do, but my skill set is not required here. It's starting to make me feel like I actually am "void Oblivion();"
I think I may retire from this thread for a few more moons. But then again, who knows. The company is good at least.
Edit:
Anyway....Once you get a your design finalized, do you think joe should try to build ONE Driver? One of the things he could do is to force it on and just hook his power supply (Input side) to a simple 120 Volt 24 hr household timer and just exercise a single pump?
Good idea.