On Wednesday 23 December 2020 19:55:48 andrew beck wrote:

> Just to tag in.
>
> I need a braking resistor for my cnc mill spindle it's a 7.5kw vfd.
>
Need pwr src voltage etc, and I'll look it up in the Huanyang book.

> Needs to rigid tap all the time etc
>
> Any ideas?  I like the idea of a stove element..
>
> Just need to know some values etc
>
> On Thu, Dec 24, 2020, 7:52 AM Chris Albertson
> <albertson.ch...@gmail.com>
>
> wrote:
> > 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
> > <to...@pgrahamdunn.com>
> >
> > 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 <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
> >
> > --
> >
> > Chris Albertson
> > Redondo Beach, California
> >
> > _______________________________________________
> > 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


Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page <http://geneslinuxbox.net:6309/gene>


_______________________________________________
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users

Reply via email to