Hi , Viesturs. I found this document<http://www.cressall.com/brakingresistors/downloads/Calculating%20brake%20resistance.pdf>that may be useful . I do believe that 100W should be ok for a 500W motor . Of course the calculation is related to the energy that have to be dissipated during the braking phase. So also acc/dec time can influence too.
Alex On Thu, Apr 17, 2014 at 4:25 PM, Kirk Wallace <[email protected]>wrote: > On 04/17/2014 06:56 AM, Viesturs Lācis wrote: > > Hello! > > > > I have three chinese servo drives in the waterjet machine and they are > > constantly faulting with "overvoltage" error. Since I have not yet added > > any braking resistors, it seems obvious that I should do so. > > The question is: how do I determine appropriate resistance and rated > power > > values for the resistor? > > Motor parameters are here: > > http://www.cutting.lv/fileadmin/user_upload/tg-motor.pdf > > > > Currently max current in motors is set to 1,4A, which makes me think that > > actual motor power is 500W. > > Experienced guy suggested braking resistor with 100-150 ohm resistance. > But > > how do I determine correct rated power? Or is it that I just take the > > biggest power available as it cannot be too high? > > > > Viesturs > > Some VFD manuals have sections covering braking resistors. Some resistor > modules have sensors or protection devices of some type. > > The Ohms and voltage values will set the current going through the > resistor. > > V = I * R > or > V / R = I, > > let's say 240V / 100 Ohms = 2.4 Amps. > > Watts = V * I or 240 * 2.4 Amps = 576 Watts. > > If you go higher in Ohms, you will get less braking. The VFD's braking > circuit will likely have a maximum current rating as well as the motor. > > One of my shop-made braking modules (four gold colored resistors) is > bolted to the back of my VFD here: > http://www.wallacecompany.com/cnc_lathe/HNC/00024-1a.jpg > > > -- > Kirk Wallace > http://www.wallacecompany.com/machine_shop/ > http://www.wallacecompany.com/E45/ > > > ------------------------------------------------------------------------------ > Learn Graph Databases - Download FREE O'Reilly Book > "Graph Databases" is the definitive new guide to graph databases and their > applications. Written by three acclaimed leaders in the field, > this first edition is now available. Download your free book today! > http://p.sf.net/sfu/NeoTech > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ Learn Graph Databases - Download FREE O'Reilly Book "Graph Databases" is the definitive new guide to graph databases and their applications. Written by three acclaimed leaders in the field, this first edition is now available. Download your free book today! http://p.sf.net/sfu/NeoTech _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
