Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: Graham Waterworth on February 07, 2006, 05:53:53 PM

Title: DC Spindle drive question
Post by: Graham Waterworth on February 07, 2006, 05:53:53 PM

Hi All,

my lathe is fitted with a 3/4 HP spindle motor driven by a KB Electronics KBLC-240-D variable speed unit.  My question is this :- Should the spindle run at the same maximum speed in CW and CCW rotation.

Mine will do 2500 rpm CCW and only 1200 CW (reverse)

The lathe manufacturer (Warco Ltd) say this is normal,  its the first time I have seen this on a vari drive.

Any comments?

Thanks

Graham.

Title: Re: DC Spindle drive question
Post by: Art on February 07, 2006, 05:58:57 PM

Hi graham:

  Many DC motors draw more current in reverse than in forward. This may be simply a current limitation of the controller..

Art

Title: Re: DC Spindle drive question
Post by: Vmax on February 07, 2006, 08:53:08 PM

I believe it has to do with the brush orientation to the commutator. Some motors have the brushes offset in one direction. I have seen some DC motors that would barely run if you reverse the polarity.