Re: ...power...

NCS,

I guess it's my fault I haven't made my point clearly. Let me try
again, using the "there is no such thing as a free lunch" method.

Motors generate mechanical power. Dyno test data I have for a 4A, 3V
double stack 34 motor (M092-FD08) is 108 Watts mechanical at 60VDC,
or a little over 1/7 HP. While it is generating that power, it
consumes 159W of electrical power for an efficiency of 108/159 or 68%.

Let's get back to the 159W. Where does it come from if not the power
supply? If you have 3 motors, then you will need 477W total. At
60VDC, 7.95A is needed to deliver 477W.

You say 0.5A at 60VDC is fine. That is 30W. How do you get 108W motor
shaft power while heating the motor with an additional 51W from a 30W
supply? Remember, there is no such thing as a free lunch ;-/

Mariss

--- In CAD_CAM_EDM_DRO@y..., NCS <ncs@n...> wrote:
> >The voltage rating on a step motor simply means if you apply 3VDC
> >across that motor's coil, 4 amps of current will flow. In other
words
> >it has 0.75 ohms resistance.
>
> Oops! I think I was being too subtle.
>
> The original post was in reference to the current required from a
power
> supply.
>
> No need for a 10amp 60 volt supply--that's 600W, enough to heat
> a small room.
>
> If three motors draw 10A max. at 3V, then one would either need
> a 3V 10A supply (not-recommended, low high-speed torque)
>
> OR
>
> a 60V supply (20 times the voltage) at 0.5 A (1/20th the current)
>
> A supply that delivers 60V at 10A is overkill.
> (I think 60V at 2A would provide a reasonable power margin.)
>
>
>
>
> >> 10A x 60 V = 600W or 200W per motor.
> >> 200W / 3V = 66.6 A per motor.
> >>
> >> Uh-oh, somethings not right!