Hi Jon, my answers to your questions are below.
> Message: 4
> Date: Fri, 30 Jul 2010 12:13:31 -0500
> From: Jon Elson <[email protected]>
> Subject: Re: [Emc-users] Another Newbie Question.
> To: "Enhanced Machine Controller (EMC)"
> <[email protected]>
> Message-ID: <[email protected]>
> Content-Type: text/plain; charset=ISO-8859-1;
> format=flowed
>
> The original Bridgeport drivers used a saturable reactor to
> limit motor
> current when not moving. At some speed the reactor
> was switched off to
> send full voltage to the motor drive. Are you
> controlling this? It is
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.
> an extra transistor on the driver board, so you need to
> drive 5 wires
> for each axis, 4 for the phases and one for the reactor
> control. If you
> are controlling the reactor transistor, you may be turning
> the reactor
> off at too low a speed, causing excessive current in the
> motor.
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.
>You
> probably are moving Z very slowly (a couple IPM max) when
> drilling, and
> if your reactor control is set to turn it off on any
> movement at all,
> that may be the problem.
>
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.
Andrew
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