Re: [CAD_CAM_EDM_DRO] Re: BP retrofit yaxis drive burnup- follow-up

Keith Clark wrote:

>Ron, we need to compare notes to see if there is a common pattern.
>Mine takes some time to burn also, but I hope my problem was having
>the relay to turn off and on the powersupply on the DC side instead
>of the AC side. Now I can't get the x axis to move properly... I
>am going to drop to half winding mode and lower current to see if
>that helps in the long run.
>
>

If these Gecko drives last several months, and then die, I would suspect
it is
a heat related problem, or possibly the current inrush is degrading the
internal
capacitor. It takes so many inrushes to wreck that cap, and then the
uncontrolled
voltage spikes destroy the power FETs. If these problems are all on systems
using a relay on the DC side, then that seems like the diagnosis. If
some of these
recurring failures are on systems without the relay in the DC side, then
heat of some
sort has to be it. It has been noted by several people that the
internal cap
in the Gecko drives runs very hot if even half a foot of wire runs
between the main
filter cap and the drive, and no external cap is used right outside the
drive.
Most of the pedestrian caps are rated for a few years life at 85 C core
temperature.

(My PWM servo amps have a fairly expensive 2.2 uF film capacitor in
parallel with
the internal electrolytic cap for exactly this reason.)

Jon