another concerns (although it seems to work) does the usb 3.0 cable has been designed to carry large current ?
(like that I would assume data transfer requires a rather small intensity and usually usb device doesn't use lot of power)
AFAICT, the USB cable is solely for data transfer and does not carry any power to the riser. Looking at the USB risers I have, I see traces for pins 11, 14, 15, & 17 (B side), and 1, 11, 13, 14, 16, & 17 (A side). 17/B and 1/A are connected and considered one so that makes 9 used pins in total, perfect for the USB 3.0's 9 wire design, and leaves no room for power. Power pins are not connected. [edit] This is why USB 3.0 cables are necessary and USB 2.0 cables won't work. The former has 9 pins while the latter only has 4.