> > --- On Sat, 5/11/13, Gene Heskett <[email protected]> wrote: > > > > > When I did the PMDX-106 for the mill, I used 2 relays, one > > to switch > > between the output of the controller with its DPDT poles, > > the back side of > > which dropped a 10 ohm 20 watt resistor across the motor to > > make use of its > > generating ability as a means of stopping it fairly rapidly. > > As in 2500 > > revs to zero in just a hair over 1 second. The 2nd > > relay was used in the > > usual DPDT reversing circuit. > > > > There isn't that much inertia in that setup, but this will > > have a cast iron > > fan cum flywheel that weighs a good 2 pounds to stop. > > So a 10 ohm 20 > > watter, taking the dump from 7000 rpm, is likely to be > > considerably hotter > > than bright red internally by the time its down to 100 rpms > > as that will > > translate to about a kilowatt of stored energy. > > > > 20 ohms won't have to take quite as much of a rapid thermal > > shock, but the > > wattage will be similar, so I don't see any way to make it > > work that > > doesn't involve a panel of at least 8 similar resistors. > > > > > > Basically anything I can make off the local walmart shelves > > (for under 50 > > bucks that is). > >
http://www.walmart.com/ip/Reliance-4-500-Watt-240-Volt-Universal-Flange-Water-Heater-Element/15815368?findingMethod=rr 12.8 ohms, 4500 watts peak (or continuous, if you put it in water). I suspect that you don't need the water given the short time needed to decel. -- John Kasunich [email protected] ------------------------------------------------------------------------------ Learn Graph Databases - Download FREE O'Reilly Book "Graph Databases" is the definitive new guide to graph databases and their applications. This 200-page book is written by three acclaimed leaders in the field. The early access version is available now. Download your free book today! http://p.sf.net/sfu/neotech_d2d_may _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
