Re: cap for geckos

Hi,

Actually the purpose of the caps is to promote a long and healthy
life for the drive. Jon is correct, PWM drives have large, high-
frequency circulating currents. Because these currents pass thru the
capacitor, they also pass thru the capacitor's ESR (equivalent series
resistance). This current causes heating (I squared R) in the
capacitor. Chronically overheated aluminum electrolytic capacitors
will dry out and make a mid-life career change from capacitor to open
circuit.

An external capacitor shares this burden and thus makes life easier
for the internal capacitor. This sharing only works if its ESR is
significantly less then a few 10ths of an Ohm. That is why the main
capacitor is of little help; the power supply wiring resistance is in
series with the main capacitor's ESR, pretty much canceling any
benefit it could contribute.

Mariss

--- In CAD_CAM_EDM_DRO@y..., Jon Elson <elson@p...> wrote:
Other details of the circuit will determine
> the susceptibility of the Gecko drive to whatever voltage
fluctuations
> are present. In serious cases, it could cause the drive to fault or
> lose position, otherwise it might cause the motors to have less than
> full power.
>
> Jon