I may be off base here, but here is my two cent's worth. My Hardinge HNC came with a Warner electric release brake. It uses a permanent magnet to activate the brake while the power is off. To release the brake, a DC voltage is applied to offset the permanent magnet. For proper brake release, the DC voltage must be adjusted high enough to release, but low enough to not go back into braking mode. My brake was completely worn out and cost from $500 to $1200 for a replacement, so I removed it and I have not had a chance to see how well it would work with my rotary converter.
As my EMC conversion progressed, it turned out that I needed to use a VFD for my spindle and coolant pump. So, now (by cheating and using the VFD's with 240 Vac) I don't need three phase for the HNC. To enhance braking, I installed a braking resistor to the spindle VFD. It brakes very well,so for normal lathe functions the VFD may be all I need. In the future, I will probably make up a pneumatic release brake for safety purposes. VFD's are now cheap enough that I may convert the rest of my machines to VFD's and get rid of the rotary phase converter. For the standard brake the HNC takes in three phase and routes two of the phases through a 240 Vac to 120 Vac transformer, then an AC solid state relay, a diode bridge and a pair of resistors to adjust the output DC voltage. With rotary phase (and most solid state) converters, two phases are 180 degrees apart (standard 240 Vac) with the third 90 degrees and from the other two and most often at a different voltage. Real three phase has three phases spaced 120 degrees apart. In my situation, since the final voltage to the brake is important, any deviation from real three phase may make the brake susceptible to malfunction. If your system uses two phases to operate the brake, like mine used to, it may be better to make sure to use the 240 Volt, 180 degree legs that go through your converter unchanged. Filtering the final DC to the bake may also help. On Fri, 2007-09-07 at 10:18 -0400, Alfred Smart wrote: > I have a magnetic spindle motor brake Reuland motor and brake. > > I run a rotary phase converter to make three phase to run my > shop ,rural area ,the converter starts 5hp & runs 10 > > When I start the motor up the brake rattles, the Wells Index people > said that its because of the unbalanced phases produced by the > converter. > the brake is wired to the motor legs and it energizes coils and pulls > the pads off the brake disc, when I run my lathe motor and I start the > index spindle it is much more stable EMF? Now that I am reading this again, your system may be different than mine. Do springs provide the power-off braking? Is the brake AC or DC and what voltage? I am guessing, you get better brake performance (less rattle) with the index spindle on because you are adding converter capacity with each unloaded three phase motor you power from the converter. I have heard that adding a flywheel to your converter or turning on unloaded equipment will help. > Short of running a idler motor any ideas what could be done to balance > my three phase legs? > Phase-A-Matic sells a stabilizer but its $360-$625 range for one sized > for my converter. At that price and some eBay shopping you can get two or three VFD's. > Sorry for posting here but I know how sharp you guys are. > Thanks Al. Good luck, Kirk Wallace ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
