Speaker To-Dirt wrote: > Jon, I am sending the phase steps (Gray Code) to the various axis boards. To > my, minimal, understanding it is the ACC board that controls the reactors. Am > I misunderstanding this? To be explicit, it was to my understanding that the > ACC board monitored each coils current and then controlled the reactor based > on the current it sensed. As soon as I'm done with this reply, I'm going to > go back into the service manual....Gosh I hope I did not get this wrong. > I am more in tune with the general technique than the actual location of the specific functions. So, you probably are right. But, I WAS under the impression that the reactor control was done by the CPU, and not sensed from motor current. The latter would actually be a much more intelligent design, and with PWM could even allow a gradual increase in voltage as speed rises. > Okay so just to be sure, it is to my understanding that the ACC board does > this. I still have that in the loop. I am replacing the the PDP-11 stack with > a PC and driving the two TTL phase step lines going into each axis controller. > > > >> > > Just to help your thoughts out. The fuses blow during, yes, slow moves, or > after I turn on the spindle. But I think the spindle induced blows were due > to me using a faster blowing fuse than specified for. With the ABC Bus Fuses > 205V 15A I have not seen that happen. > > >> If your transistors were going into thermal runaway, then >> it is very >> unlikely the drive would work after you replaced the fuse. >> > > While doing searches on this problem, I came up on several of your other > posts on the problem. Jon, you're quite the expert and Google thinks highly > of you on the subject. In those posts you mention that BOSS <=5 machines like > mine, don't like being run off of rotary phase converters. As another data > point my loaded voltages RMS Phase to Phase are thus 209-209-189. Is my > co-generated 189 too far out of balance to cause this problem? I'm not sure > my Z transformer is getting the co-generated phase, but some of your past > posts point in the direction that troublesome axes usually are getting the > low phase on home shops like mine. > OHHHHH! My understanding of the way Bridgeport did this, necessitated by the use of the reactors, is that each phase OUT of the transformer serves one axis. So, if one phase is low or high at the input, then one axis gets a different voltage. That could be part of the problem, also you could have a fluctuating voltage. I assume this SAME RPC runs the spindle motor? Then, your generated phase almost certainly changes voltage when the spindle is started. Your comments attributed to me don't ring a bell, I think they may be from someone else, but in a thread I may have contributed to also. There is a procedure in the Bridgeport book to set the current in the reactors by adjusting to get a specific voltage across a resistor. This has to be redone when line voltage changes. If your generated phase is shifting, this setting can't stay in the correct range. There is a procedure for adding capacitors to RPCs that stabilizes the generated phase much better under load changes. 189 Volts is 10% low, so that is a significant imbalance.
I have a couple things I can advise. First, I hate RPCs, much prefer a VFD. You get variable speed, reversing, braking, motor protection and phase converter all in one unit, get rid of all those motor starters with heater coils. Then, there are FAR more advanced stepper drives available. Unfortunately, one of the best, the Gecko 201-203 series, is just a little marginal for the big Bridgeport motors. Still, many people find they work well at the drive's rating of 7 A. The ultimate seems to be to swap out the size 42 motors for modern size 34 at the same time. Of course, now you are talking about real money, too, and could make the upgrade to a servo system for about the same outlay. Anyway, I'm not sure what is going on there, and I only THINK it may have to do with your RPC and fluctuating generated phase voltage. So, this thing blows fuses, but never blows transistors? That sounds pretty strange, most people who try to keep those Bridgeport drives working do suffer blown transistors from time to time. If you have not performed the current setting procedure on these drives, you really need to do that. I do not have the procedure, but if you don't have the maintenance book, somebody on CNC Zone should be able to provide the info. You should check the reading with the spindle both off and on, and if you can't keep within the specified range in both cases, then the RPC needs to have balancing capacitors added to it. Jon ------------------------------------------------------------------------------ The Palm PDK Hot Apps Program offers developers who use the Plug-In Development Kit to bring their C/C++ apps to Palm for a share of $1 Million in cash or HP Products. Visit us here for more details: http://p.sf.net/sfu/dev2dev-palm _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
