For my 1.5kw Hitachi WJ200 drive, the manual recommends 50 ohm. However, they want you to buy their resistor so they don't spec a recommended wattage. I ended up using a 400W wirewound resistor from Ohmite, part number ARG400C50RJ. It didn't even get warm when I was running my rigid tapping testing with back to back reversals and the shortest ramp times that gave reliable performance. I'd think 400-600W should be ample for a normal duty cycle, even on a 2.2kW drive with aggressive ramp times.
On Tue, Dec 22, 2020 at 7:18 PM Chris Albertson <[email protected]> wrote: > The brake resister depends on what duty cycle you run the motor at. It > you only run forward at a constant speed you will never use the resister. > But if you continuously run the motor to full forward then full backward > speed for hours you will be heating the resister with about 50% of the > motor's full power So over 1KW. Then add a "safety factor" or say 1.5 > and you get a 1.5KW resistor. But I doubt you'd do a worst-case back and > forth motion. > > One way to save a few $$ is to install a fan in the resistor with a > thermostat. The best load resisters I found per dollar are those ones > on eBay made with wires over a ceramic tube. Buy several and you can > adjust the resistance by writing series/parallel in different combinations. > > A low resistance will be a more effective brake. But do not go too low. > Calculate the current. If the motor has 200 volts across it and you sort > the leads through a 1 ohm resistor then you get 200 amps and maybe the > motor is only rated at 20 amps and you blow up the motor. > > The most efftive brake is a length of wire. The worst one is an open > circuit. I think maybe a compromise is to use a resister then same > inpedence as the motor. > > I knew some one who found he could use a stove heating element as a load. > They are cheap > > Wild guess? maybe 50R at 1 KW peak with much lower average W ratiing. > > > > > On Tue, Dec 22, 2020 at 3:25 PM Gene Heskett <[email protected]> wrote: > > > Greetings all; > > > > Swapping a 110 volt vfd, for a 250 volt vfd, one of the terminals is > > labeled differently, the common point of the fwd/rev/spd1-2-3-4-5 > > terminals on the 110 volter is labeled XGND > > > > But the common point terminal on the higher voltage unit is labeled DCM > > but the diagram of how to hook up external controls is identical. > > > > Is there any good reason to treat it differently in hooking it to a > > 7i76D? It should all be equ as its the presence of continuity from the > > fwd/rev terminals to this XDNG/DCM common point that determines the > > command. > > > > There is no terminal labeled neutral on this controller, only a marked > > static ground which I ran back to the services static bar, not to the > > neutral bar. But my copy of the NEC is now 24 years old, so I'm asking, > > hopefully, someone with a more recent copy. > > > > This is also the first vfd I've had that actually has hookups for a dump > > resistor. 2.2 kw vfd & motor, running on 250 volt single phase, what is > > good value and wattage for this resistor? > > > > Thanks folks. > > > > 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 > > [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 > -- Matthew Herd Email: [email protected] Cell: 610-608-8930 _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
