Re: [CAD_CAM_EDM_DRO] Re: Electrical wizards

Chris L wrote:

> Alan Rothenbush wrote:(snip)
>
> > For example, in a Sherline sized unit, with appropriately sized
> > steppers, I doubt that there is much meaningful difference between 18 volts
> > and 36 volts.
>
> I was always to understand that "double" the voltage actually could double
> torque and speed maximums. Is this true ? Or is your statement really toggling
> on the "Sherline" type application where voltage used may not show up as well as
> in a larger machine ?

Not really. You can't double the torque, as the steppers are almost
certainly already operating (at zero speed) at their rated current.
The torque falls off rapidly as the motors accelerate, and especially
on bipolar drives, a higher voltage allows them to reverse the current
flow in the windings faster, and therefore develop more torque at
higher speeds. I don't think you can really get a 1:1 improvement,
ie. doubling torque at some speed when you double voltage. You
may get close to that if the existing power supply voltage is really
marginal, though. You also generally increase heat in the driver AND
in the motor at higher voltages, due to eddy and hyseresis losses
in the iron, primarily.

Jon