Re: gecko's and voltage

Kim,

It's not a matter of petitioning; it's a matter of what is possible
for the price.

1) The MOSFETs used in the G320 are IRF540s. They are rated at 100V
and 27A. The MOSFET "chip" is as large as the TO-220AB package can
accomodate.

2) A characteristic of MOSFETs is the "on" resistance increases as
the square of the rated voltage for a given chip size. This means to
carry the same current at twice the voltage, the chip area would have
to be 4 times as large.

3) The next higher common rated voltage for MOSFETs is 200V. At that
voltage the drive rating would become 160V and it would be rated for
only 5A. Higher current ratings would require the much bigger (and a
lot more expensive) TO-247 package.

Other ramifications (read expensive) would be a linear voltage
regulator would no longer be usable because of excessive dissipation.
A switching type regulator and its attendant circuitry would have to
be used.

The drives are tested at 100VDC and come apart above 108VDC. It is
not good practice to rate equipment at 100% of the component max
ratings. We use 80% as the de-rating value for reliability.

Mariss

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Kim Lux <lux@d...> wrote:
> We need to petition Gecko to make their drivers work with 90+Volts.
> Many of the good servo motors are rated for 90V and step down
> transformers offer very good VAs for the money.
>
> Kim