Re: SCR DC Motor Controllers... Need Advice.

Hi Mariss,

Thanks for the detailed response. Thats exactly what I wanted to
know. I was unsure if the controllers operated this way or just
worked the same as reducing voltage (which would also deacrease
stall torque). Perfect explanation. You always seem to have a way of
making us "no so electronicly minded" people understand concepts.
Thanks again!

Mark




--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Mariss Freimanis"
<mariss92705@y...> wrote:

> Mark,
>
> This is best understood by drawing a graph. Make the +Y axis RPM.

Put

> a point on the axis at 1". Make the +X axis torque. Put a point on
> the axis at 1" as well.
>
> Connect the 2 points. That is the motor load-line.
>
> Now draw a horizontal line starting from 0.1" on the +Y axis. Draw
> another horizontal line staring from 0.9" on the +Y axis.
>
> The line starting from 0.1" is the speed-torque curve when the

speed

> control is set to 10% of full speed. Note how you can increase

torque

> load to 90% of stall before the speed begins to drop.
>
> The line starting from 0.9" is the speed-torque curve when the

speed

> control is set to 90% of full speed. Note how you can increase

torque

> load to only 10% of stall before the speed begins to drop.
>
> Those are the results you will get.
>
> Mariss
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "mmurray701"

<gmurray@n...>

> wrote:
> > I need some advice about SCR drives. I need to know if they

provide

> > constant torque at all speeds. For example if the controller is
> > set to half speed, is the torque also reduced to half or does it
> > remain constant? And finally, will there be any difference in
> > performance in a motor running from a 90v SCR drive set at full
> > speed, and a motor wired directly to a 90v source? Thanks in
> advance!
> >
> > Mark