Re: [CAD_CAM_EDM_DRO] BP series 1 Boss 4 to EMC Gecko drive Power Supply retrofit

Edgar wrote:

>I recently acquired a working 1978 Boss4 Series 1 Bridgeport with the
>Vram head. My shop runs on 480V 3phase, and I can't stand the thought
>of throwing out a perfectly good power supply when I should be able to
>use it!
>In looking over the schematics
><http://keycoldstorage.com/BPsyswiring_pg4-113_small.gif> for my
>Bridgeport, I find a power
>supply <http://keycoldstorage.com/BPsyswiring_pg4-113_detail.gif>
>style that I am not familiar with. In searching the Yahoo cam
>group, as well as CNCzone, I was not able to find anyone who had
>described using the existing three phase supply during a retrofit; but
>much of that I liken to most of the users' desire to switch to single
>phase given the opportunity.
>In any case, this supply appears to have some sort of voltage
>following or normalizing type circuit to balance the three phases in
>DC. I have seen the secondary transformers described as both bucking
>transformers and line reactors, neither of which I believe are
>accurate based on the scematic. I could be completely off base,
>correct me if I'm wrong. The truth is, I'm not against building a new
>supply, but my dad is not for throwing away such "perfectly good
>iron!" and I really don't care about speed for this machine. So the
>question is really whether or not it is worth it to simply tap the
>supply in a similar fashion to the original Bridgeport drivers (see
>attached schematic), or to yank it and build anew? If I do use the
>existing supply, where should I tap in to best preserve the new Gecko
>202 drivers and my old Superior motors?
>
>

The Bridgeport BOSS stepper power supply is really 3 power supplies on one
transformer core. They follow the AC output of each secondary winding
with a
reactor. This reactor has another winding on it where a small DC
current saturates
the iron, and reduces the inductance drastically. This winding is turned on
when the axis in in motion, and it raises the voltage supplied to the
motor to
about 56 V DC. When the axis is not moving, the winding is turned off, the
reactor's inductance returns to normal, and it reduces the DC supply to
about
9 - 12 V DC, thereby reducing the voltage across the motor and preventing
overheating.

So, the three secondaries provide 3 totally separate DC power supplies.
After
pulling the reactors out, you should be able to set up a 3-phase
rectifier and
get a single, very heavy-duty DC supply. I think you'll get 56 V DC out
of it.


Jon