Re: [CAD_CAM_EDM_DRO] Re: Stepper de-rating

bull2003winkle wrote:

>Mariss:
>
>Thanks, does this mean that if I want to use steppers I should expect
>an 80 deg. C operating temperature even with a good drive like the
>G201.
>

80 C? I've run some size 34 motors all day, and they don't get anywhere
near this hot on a G201. I was running about 36 V DC, I think. Higher
voltage makes them run hotter, so only use a higher voltage if it is
absolutely needed for large high inductance motors. I was running the
size 34 motors up to 1440 RPM (90 IPM on a minimill)

> I understand eddy currents and iron losses but I guess I did not
>realize they were that large. Is this true if you turn off drive
>current after a motion. My application only calls for motion at less
>than 10% duty cycle and the lead screws cannot move the stepper when
>it is off.
>

The G201 automatically reduces motor current when not moving. I think
it drops to 33% of full current.

>
>The only reason I thought about steppers in the first place is that I
>want to keep the handwheels and their micrometer dials. None of these
>problems exist with servo motors but they are geared down and hard to
>turn manually.
>
>

Are you sure? I often find servo driven machines much easier to turn than
steppers. You do notice the extra inertia from the servo motors, but that
is a small thing.

Jon