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

I was going to do this with my Series 2 Boss 6, but couldn't tap thethree phase transformer at less than 62VAC. Rectified, this wouldyield about 87VDC, which is above the max voltage rating for the G202Gecko drives I am running. I
ended up re-purposing the 230/115VAC isolation transformer, feeding it115VAC. The resulting DC voltage from this setup is right at 80VDC,which could easily exceed the G202's 80VDC rating if the power companyraises the voltage as they do from time to time... I have been runningthis way for over a year with no issues. If you consider doing this,be aware that Geckodrives may not honor any warranty repairs if youkill a drive due to over voltage!

I am also running the original Boss Superior brand stepper motors. Ihave my G202's set for NEMA42, and do not have any current limitresistors installed. During testing, I was able to achieve 180ipmrapid on X, 160ipm on Y and 200ipm on Z just before stalling eachaxis. I have the rapids limited to 120ipm for reliability. I have hadzero problems with lost steps! The key to being able to run thefactory steppers reliably at 120ipm, is providing the stepper driveswith very stable pulse trains from my PicoSystems USC board.

Good Luck with your conversion!

/Craig.

Jon Elson wrote:

Edgar wrote:

I recently acquired a working 1978 Boss4 Series 1 Bridgeport with theVram head. My shop runs on 480V 3phase, and I can't stand the thoughtof throwing out a perfectly good power supply when I should be able touse it!In looking over the schematics<http://keycoldstorage.com/BPsyswiring_pg4-113_small.gif> for myBridgeport, I find a powersupply <http://keycoldstorage.com/BPsyswiring_pg4-113_detail.gif> style that I am not familiar with. In searching the Yahoo camgroup, as well as CNCzone, I was not able to find anyone who haddescribed using the existing three phase supply during a retrofit; butmuch of that I liken to most of the users' desire to switch to singlephase given the opportunity.In any case, this supply appears to have some sort of voltagefollowing or normalizing type circuit to balance the three phases inDC. I have seen the secondary transformers described as both buckingtransformers and line reactors, neither of which I believe areaccurate 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 newsupply, but my dad is not for throwing away such "perfectly goodiron!" and I really don't care about speed for this machine. So thequestion is really whether or not it is worth it to simply tap thesupply in a similar fashion to the original Bridgeport drivers (seeattached schematic), or to yank it and build anew? If I do use theexisting supply, where should I tap in to best preserve the new Gecko202 drivers and my old Superior motors?

The Bridgeport BOSS stepper power supply is really 3 power supplies on onetransformer core. They follow the AC output of each secondary winding with areactor. This reactor has another winding on it where a small DC current saturatesthe iron, and reduces the inductance drastically. This winding is turned onwhen the axis in in motion, and it raises the voltage supplied to the motor toabout 56 V DC. When the axis is not moving, the winding is turned off, thereactor's inductance returns to normal, and it reduces the DC supply to about9 - 12 V DC, thereby reducing the voltage across the motor and preventingoverheating.So, the three secondaries provide 3 totally separate DC power supplies. Afterpulling the reactors out, you should be able to set up a 3-phase rectifier andget a single, very heavy-duty DC supply. I think you'll get 56 V DC out of it.JonAddresses: FAQ: http://www.ktmarketing.com/faq.html FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/Post
Messages: CAD_CAM_EDM_DRO@yahoogroups.com Subscribe: CAD_CAM_EDM_DRO-subscribe@yahoogroups.com Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@yahoogroups.com List owner: CAD_CAM_EDM_DRO-owner@yahoogroups.com, wanliker@..., timg@...: pentam@... indigo_red@... davemucha@... [Moderators] URL to this group: http://groups.yahoo.com/group/CAD_CAM_EDM_DROOFF Topic POSTS: General MachiningIf you wish to post on unlimited OT subjects goto: aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if you have trouble.http://www.metalworking.com/news_servers.htmlhttp://groups.yahoo.com/group/jobshophomeshop I consider this to be a sister site to the CCED group, as many of the same members are there, for OT subjects, that are not allowed on the CCED list.NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM. DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........billList MomList Owner Yahoo!

[Non-text portions of this message have been removed]