if my 125A fuse (Rodeo) does not blow in 1 second with the TS40 peak current flowing through it then I'll buy a lottery ticket !
I expect it will. Who said it wouldn't? By "peak current" I assume you mean short circuit current, not the 10C pulse rating the manufacturer gives. Something like 25C to 30C when hot.
We are talking HRC semiconductor rated fuses here. Not BS88 fencing wire !
Good point. I wasn't thinking semiconductor fuse when I estimated those 100 second and 25 second overload ratings. But that doesn't affect the continuous rating.
Fusing is intended to protect against s/c conditions. Overload is controlled by VFD.
I'm not yet convinced of that. I don't think AS3000 would consider that sufficient overload protection. I don't think semiconductors are acceptable for that. What protects the cables from an overload due to a drive fault? Surely your VFD manual recommends fuse sizes and
cable sizes. What does it recommend?
Otherwise you must design wiring cont for max battery current !
Not sure what you're saying here. You would only need to design wiring for battery s/c current if you had no fuses (or CBs etc), which would obviously be ridiculous.
The wire cont amp rating is so temperature and enclosure dependent as you note. Whatever number you chose, my cont current is 40A (22kW). This is below even the most pessimistic of the predictions.
Agreed. It's the 125 A fuse rating that I'm questioning now.
My wire data says 85°C open air for the table in my last post.
That's good. But still won't give 120 A CCC through 2 x 6 mm^2 when in conduit. And I wouldn't want other folks to assume that any old 6 mm^2 wire can do 60 A continuous.
You did get the point that 2 x 6mm are better than 1 x 12mm when it comes to CCC ?
Oh sure. Well aware of that. Was considering doing it myself.
Keeping in mind that your power expectations may be more than mine !
Yes, I have been keeping that in mind.
It is good to see that you have convinced yourself that my arrangement is neither over nor under-engineered.
Except for that fuse. Why do you think you need
a 125 A fuse? Can you point us to its time-current curves?
If you need
that fuse in order to tolerate your peak current requirements then I think you need at least 2 x 10 mm^2 wire, at least where it runs in conduit or other air-convection-restricted area.
However one thing I haven't taken into account is that with an EV you may never really get to a continuous rating for cables and fuses since the batteries typically last less than 90 minutes at max cruising speed. But why engineer it so close to the bone.
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).