i have curtis pmc pwm unit. 24v dc.
on the speed pot circuit, i used one 10k resistor in series with 10k pot to control 12 volt minn kota troller. max speed is set at 12 volts output. 24v dc input. it works on troller, and also on 24v dc motor to drive straight shaft out boat(kinda long tail drive) with prop on the end.
gerald b.
From: greenpjs04 <greenpjs@neo.rr.com>
To: electricboats@yahoogroups.com
Sent: Friday, October 7, 2011 10:29 AM
Subject: Re: [Electric Boats] trolling motorWe need to be careful here. It is true you can use a higher voltage on a motor as discussed below, but the original poster was asking about a trolling motor. A trolling motor is a motor plus a controller built in. I would never recommend running a 12V trolling motor at 24V unless the manufacturer specifically said it was OK. It might only last a few milliseconds before the electronics fried. The motor itself would still be OK, but the "trolling motor" purchased product would be dead.
Pat
--- In electricboats@yahoogroups.com, Ben Okopnik <ben@...> wrote:
>
> On Thu, Oct 06, 2011 at 08:17:11PM -0700, Femm wrote:
> >
> >
> > Ahhh Gerald I hate to tell you this but you are still feeding 24 volts to that
> > motor...
>
> True enough... but it doesn't actually matter, since motors don't really
> care about voltage. What matters is the total power dissipated across it
> - which is what PWM is intended to control. In a DC application, the
> voltage would determine that P(d) by working across the resistance
> presented by the motor, which would result in a given current - but PWM
> is not DC. You could, theoretically, apply 100kV across a motor; as long
> as you pulsed it at a low enough duty cycle, that motor would work
> perfectly, last just as long, etc. (Granted, 100kV would have its own
> problems - spark gaps, for one - but the overall point remains valid.)
>
> I used to design pulsed power systems for Hughes Aircraft way back when.
> If we had tried driving those Gunn and IMPATT diodes that we were using
> with DC to the output levels that we needed, we would have sent them up
> in a cloud of smoke in literally fractions of a second. With PWM, we got
> incredible power densities, and enough signal strength that we routinely
> bounced our millimeter-wave signals off the Moon as a test. Great heat
> transfer characteristics, too (although I don't recall the physical
> basis for why that was the case.)
>
> Voltage/resistance ratios - i.e., Ohm's Law - aren't all that applicable
> once you start chopping the drive power. Especially around inductors,
> which motors are.
>
>
> --
> Ben Okopnik
> -=-=-=-=-=-
>
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