Quote Originally Posted by routercnc View Post
Ok, thanks. Then I'll stay with my original plan which is 6A MCB type D on AC side of PSU, and automotive blade fuses on the 70V DC side. I plan to fit a trial 1A fuse on the DC then jog an axis to deliberately blow the fuse.
Interrupting the supply to a stepper motor driver (or many drivers for that matter) whilst running can damage them, so I wouldn't recommend that test.

Quote Originally Posted by routercnc View Post
Do you know if the 5x20mm fuses need to be specific for DC? This was where I got stuck with this option because reading around AC and DC currents seem to require a different type of fuse and so I went back to the automotive type which are definitely for DC.
I read somewhere that if the DC rating isn't specified for an AC fuse, you can use it with DC but only at half the AC voltage rating. Don't quote me on that though...
I would trust the 5x20mm fuse more than the blade fuses - running a 240V AC fuse at 70V DC seems more reasonable than using a 12V DC fuse at 70V DC.