Re: [CAD_CAM_EDM_DRO] Re: High voltage servo controller

vrsculptor wrote:

> Mina,
> If you are adventurous and electronically savvy there is also the UHU
> high power step direction drives (160+ volts, 25 amp) at less than
> $200 each. The drives are in beta mode and only available as kits.
> There are some videos posted by satisfied users on the site.

Oh, man, don't believe it! I critiqued the UHU at last year's
CNC Workshop for a guy, and I think I went on for nearly a solid
HOUR detailing what he'd done wrong. The freewheeling diodes
are standard rectifiers, and about 1000 times too slow to
protect the FETs. The gate turn-on resistors are 270 Ohm, which
causes insane switching losses in the FETs, but it has to, to
save them from the destructive effects of unclamped inductive
pulses from the motor, since the diodes are too slow. The
current sensing circuit is blind to recirculating current and
braking of the motor, since it only has one sense resistor.
The power circuit topology is poor, with large loop areas.

If you think you can get it to run at 160 V, go ahead, but be
sure to wear ear muffs and goggles when testng it under load.

(There seems to be a new version 3 board, maybe it has
incorporated some of these improvements.)

Jon