Kirk Wallace wrote: > On Sat, 2008-01-12 at 07:47 +0000, Steve Blackmore wrote: >> On Fri, 11 Jan 2008 16:28:14 -0800, you wrote: >> >>> On Sat, 2008-01-12 at 00:01 +0000, Steve Blackmore wrote: >>> >>>> I use KBIC speed control on my mill, I simply reverse the DC output >>>> using a 20A DP/DT relay. >>> You don't switch it while the motor is running, do you? The KBIC manual >>> says that you will damage the controller by doing that. I have had >>> another look at the schematic and I am thinking that if you disconnect >>> the armature, you will get a voltage spike high enough to cause SCR1 to >>> conduct in reverse. If SCR2 is on, which is likely, you will have a >>> direct short between the mains, L1 and L2. >> No - there's a delay set on CW/CCW. >> >>> I think if inhibit is invoked long enough ( 20ms ?) to insure that both >>> SCR's are off, switching the armature will be okay. I just won't know >>> for sure until I try it. Which will have to wait until I get the parts >>> to fix the controller due to my last experiment. >> It needs to be long enough to ensure there is no output from the KBIC or >> back emf generated by the motor under any condition - I use 1 second. > > I think the SCR's and diodes are rated for 1kV, so if the back EMF is > kept to a couple of hundred Volts, it should be okay, especially if a > braking resistor is used. I think a short inhibit should be enough to > get through the initial switching spike. > >> On a mill that should be plenty, on a lathe, however, where there may be >> lots of inertia due to a heavy chuck, it may need to be longer. >> >>> I am playing with ideas on how EMC could be used to enhance what people >>> already have. These KBIC controllers seem to be quit popular. >> EMC should already run one fine, if you use an external isolator board. >> >> Steve Blackmore > > My vision is to have EMC be able to control the spindle from full > forward to stop, or full reverse within a second. Or, at least, well > enough to do rigid tapping. >
I'm not personally familiar with the KBIC drive, but I bet it is a non-regenerative drive. You will find it difficult or impossible to do a quick stop and reverse with it. A non-regen drive can only slow down by friction and drag, not by actively extracting power from the motor. Regards, John Kasunich ------------------------------------------------------------------------- Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://ad.doubleclick.net/clk;164216239;13503038;w?http://sf.net/marketplace _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
