Yes, as I wrote above, the resister specs depend a lot on how often you intend to reverse the direction of the spindle. And how quickly.
A resister of "infinite" resistance (open circuit. eg "no resister at all") can work but will give lower performance braking power. This would be "good enough" for many cases but maybe the intended usage is to do rigid tapping on thousands of holes at the highest possible rate in a production environment. I think in this case, just compromise. A resister at the higher end of the resistance range would not need so many Watts rating. "i^^2*r" will tell you. On Wed, Dec 23, 2020 at 5:50 AM Todd Zuercher <[email protected]> wrote: > I doubt you'd really need a braking resistor for running a router spindle > (what I believe you have.) Simply test it without one, as long as you > don't get overvoltage alarms on the VFD when decelerating you should good > without it (assuming your VFD has adequate safety alarms which might be a > big assumption with a Chinese piece.) > I've not run into a machine that uses one myself, but I only work with > large commercial router machines. (not any mills or lathes) and router > spindles don't have the rotating inertia that other machines like a lathe > might or the need to stop super fast. > > Todd Zuercher > P. Graham Dunn Inc. > 630 Henry Street > Dalton, Ohio 44618 > Phone: (330)828-2105ext. 2031 > > -----Original Message----- > From: Jon Elson <[email protected]> > Sent: Tuesday, December 22, 2020 8:51 PM > To: Enhanced Machine Controller (EMC) <[email protected]> > Subject: Re: [Emc-users] Checking vfd hookup question? > > [EXTERNAL EMAIL] Be sure links are safe. > > On 12/22/2020 06:30 PM, Matthew Herd wrote: > > In my research on resistor sizing, I heard reports that Haas uses stove > elements for their braking resistors. On factory machines, no less. Of > course that’s second hand, so I can’t say it’s true. > > > > > Yes, absolutely. Our Haas at work has a stovetop element in a screen > guard on the back of the machine. > All of them are made like that. It is a perfect solution for a 240 V > machine. But, for the smaller VFDs you want a small stovetop element so it > doesn't draw excessive current. Assuming a voltage doubler on a > 120 V VFD, it will still have 340V or so DC on the DC link, same as a 240 > V VFD. A 40 Ohm element should draw less than > 10 A, which should be safe for anything but the smallest VFD. So, get the > 7" stovetop elements, not the 11" ones. > > Using too low a resistance won't harm the MOTOR, it will blow the power > brick in the VFD. > > Jon > > > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
