Hi Pierce,

The problem gets much simpler now that you've described it completely. You
don't need a high side driver, that makes it much easier. You can either
use a gang of mosfets on the low side with a gang of freewheel diodes on
the high side, or a half bridge, but pinch off the high side so you only
use them as diodes.

Use a switch or contactor if you need reverse. You are racing, you want to
minimize conduction losses in your silicon.

Please explain why you want to make your own speed controller instead of
using something like a Curtis PMC?

If you really want to build your own, use lots of mosfets. Keep your
conduction losses to .75 volts or less.

Don't try to drive a gang of mosfets straight off of a PIC or Basic Stamp,
you need more current to overcome the capacitance and Miller effect in the
mosfets.

-Bob


On Mon, 15 Sep 1997, Pierce Nichols wrote:

> On Mon, 15 Sep 1997, Steve Smith wrote:
>
> > The voltage is rather low for IGBT's so the best answer is to look at FET
> > bridges. Try Seimens, Semikron, IXYS, Toshiba or IR all offer a range of
> > large FET's / IGBT's and drivers to interface to logic. With FET's watch the
> > RDSon as this can be the major power loss at these voltage levels. Is it
> > possable to increase the DC link voltage and hence decrease the current and
> > losses ?
>
>         Well, it's 36, not 26 volts. And no, it can't go higher because
> it's for a speed controller for a Solar Splash boat, and the rules limit
> us to 36V battery voltage, and 54V peak RMS. No way around it.
>
>         Pierce Nichols
>