Gene Heskett wrote: > > It sounds as if its a 3 phase AC motor turning a DC generator which in turn > powers a DC motor that actually drives the spindle? > Essentially right. > For those DC controls, I'd think it would be a lot more power efficient to > toss the rheostats in favor of pwm controlled hexfet power devices that > linuxcnc can control directly by using opto-isolation techniques which > would give 10 to 1000 times faster control, with perhaps 1/100th (or less) > of the power losses the rheostats will have, directly from a quadrature > sensing disk and opto-interrupter detection of not just spindle speed, but > spindle position in real time as it rotates. > Lathes don't really need to change speed on a dime. The spindle is not usually used as a positioning axis. The rheostats control generator field and motor field, and are not that large. For low-speed range they control the generator field, then for the high speed range they weaken the motor field.
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