This is the second time I fried 2 FMD2749A stepper drivers on my TravelCNC.
Made 2 giant Hackcenter calls at the 30C3 hacker congress stink of fried electronics while the people from CCCfr ripped out all power cables they could find, called me and got a fire extinguisher.
The drivers are advertised to be operated at up to 50V.
The first one had a 5V DC converter (LM2576S-5.0) inside that is only rated up 45V instead of an " LM2576HVS-5.0" rated up to 60V.
I'm using them with a common 48V power supply. Well within the rating of the dealer.
Now, after 3 fried stepper drivers the dealer "Thomas Wu" answered that the drivers where actually only good for 45V!!!
I wouldn't ever but any power electronics from this Thomas Wu guy on Aliexpress again!
I turned down the power supply to 44.5V (can't go lower then that on the potentiometer)
and am waiting for some new 5A drivers with over-current, over-heating, under-current,... protection.
One of these drivers is working fine at 48V driving the super-strong 4th axis, so I hope they will hold up.