Re: Adequate torque from VFD driven motors?

The latest small to medium size machining centers and lathes often
have direct drive spindles that make maximum torque at as low as
100rpm


--- In CAD_CAM_EDM_DRO@y..., "Carol & Jerry Jankura"
<jerry.jankura@s...> wrote:

> In two words - feedback control. If you were to simply drive your

motor by a

> variable voltage source, you would be correct. But, if you

monitored

> something (for example, motor speed or back emf of the motor) and

adjusted

> the voltage to hold the motor speed constant, you'd find that your

torque

> would improve.
>
> -- Jerry
>
> |But VFD's have been recommended on this list, and most new

commercial

> |CNC machines seem to control spindle speed this way. So how can

this

> |be?
> |I am retrofitting a lathe that had an elaborate mechanical

variable

> |speed drive, and it would a lot easier to go the VFD route,

especially

> |so CSS could be implemented. But I just don't see how there could

not

> |be a lack of power at lower speeds. What am I missing?