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 <el...@pico-systems.com> Sent: Tuesday, December 22, 2020 8:51 PM To: Enhanced Machine Controller (EMC) <emc-users@lists.sourceforge.net> 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 Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
