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View Full Version : Bridgeport Boss IV run on a Rotary Phase Converter ?



KiloBravo
10-20-2010, 09:39 PM
I have my brand new 1977 Bridgeport Boss IV sitting in my garage waiting for 208V of 3 Phase power ;) Can I build a Rotary Phase Converter for it or should I explore other options ? Questions, comments, suggestions ???

Just looking for some guidance as I do not have 3 phase power at my house

Thanks,
Kevin

http://farm5.static.flickr.com/4151/5087931710_92aee4c975_z.jpg

macona
10-21-2010, 12:36 AM
I think the spindle is the only part that needs three phase.

davidh
10-21-2010, 09:14 AM
can these motors on bridgeports be re-wound to 220 single phase ? or is that like buying a new motor as far as $$$$ is concerned ?

sdeering
10-21-2010, 06:51 PM
The CNC part needs 3ph too. I ran mine on a home made phase converter with the old control till I saw the light. Now my CNC control is 110. Still 3ph for the quill though.

Stephen

KiloBravo
10-21-2010, 09:05 PM
The CNC part needs 3ph too. I ran mine on a home made phase converter with the old control till I saw the light. Now my CNC control is 110. Still 3ph for the quill though. Stephen

Care to shed some light ? So I guess you did a retrofit ?

I stopped by my Stock supplier, they used to have a bunch of cheap 3 phase motors laying around. Th guy told me they sent them to their other yard :mad:

The other yard is far away and probably not worth the drive !!!

So now I have a nice Bridgeport and no way to power it :eek:

sdeering
10-22-2010, 11:31 PM
I think my phase converter is 7hp. Probly could be smaller now. Look at auctions for a surplus 3ph motor maybe.

You may be able to get the mill working as it is origional as I did, but the new software and parts will give you almost endless possibilities.

I removed all the origional control and used a campbell breakout board, home made 70v DC power supply, Larken drives, Mach3 for software.
I have since made a rotary A drive out of a rotary table.
Hears my latest project.
I have a boss5 too. the x travel is 18" so I had to do this fluting in 2 parts.

http://img.photobucket.com/albums/v510/sdeering/DSC00582.jpg

Hears a little engraving I am going to do for a fella on a 3/8 round.
http://img.photobucket.com/albums/v510/sdeering/savagetoolpath.jpg

gnm109
10-24-2010, 11:34 AM
Care to shed some light ? So I guess you did a retrofit ?

I stopped by my Stock supplier, they used to have a bunch of cheap 3 phase motors laying around. Th guy told me they sent them to their other yard :mad:

The other yard is far away and probably not worth the drive !!!

So now I have a nice Bridgeport and no way to power it :eek:


I just built a 5 HP 3 ph rotary phase converter for my Webb 4VH mill. It is an excellent way to power a manual metal-working machine, especially if you are on a budget and already have a machine with variable speed capability.

While I'm no expert on CNC, I have been investigating rotary phase converters for several years and have owned one other commercially-built one. I recently sold it since it was underpowered for my machine.

Speaking of comercially-available rotary phase converters, there seem to be two grades advertised. "Suitable for CNC"and "Not suitable for CNC". The difference is apparently in the quality of the build and the level of voltage and current control. There is a noticeable difference in price too.

The cheaper "non-cnc" versions are built to a price with little attempt to balance line outputs. That was the case with my former unit. I finally did match the line fairly well but it took a couple of capacitor swaps to make it right.

If you don't pursue building your own RPC, you could look on eBay or elsewhere and find a suitable unit. Good ones aren't cheap, however.

There's also the possibility of using a VFD but I don't know enough about those to comment.

Perhaps someone with more knowledge of just what sort of RPC is best for CNC work might come on and tell us.

Good luck.

KiloBravo
10-24-2010, 12:45 PM
Perhaps someone with more knowledge of just what sort of RPC is best for CNC work might come on and tell us.

Good luck.

Yes, that's what I was hoping for. The "unbalanced" third leg seems to be the probable for CNCs and RPCs. It seems the voltage on this leg is usually not well regulated and causes problems for the CNC drives. It seems OK to just power the motors and they don't need tight voltage regulation.

I have a line on a 10HP motor and will probably build an RPC from that if it works out. My other options is rebuilding with this kit
http://www.dmm-tech.com/index.html

Anybody buy from the guys ?

Thanks,
Kevin

gnm109
10-24-2010, 01:41 PM
Yes, that's what I was hoping for. The "unbalanced" third leg seems to be the probable for CNCs and RPCs. It seems the voltage on this leg is usually not well regulated and causes problems for the CNC drives. It seems OK to just power the motors and they don't need tight voltage regulation.

I have a line on a 10HP motor and will probably build an RPC from that if it works out. My other options is rebuilding with this kit
http://www.dmm-tech.com/index.html

Anybody buy from the guys ?

Thanks,
Kevin


The third leg can be balanced. I've discovered that increasing run capacitance will raise voltages and lowering or removing it will lower voltages, at least in the case of my new RPC.

Here are some pictures showing the one that I just finished. The voltages under load are:

L1-L2 (line) ------------242.5
L1-L3 (generated leg)-- 232.5
L2-L3 ----------------- 231.0

With 520 f start capacitance, startup is immediate. The run caps are 100 f total in parallel - 50 f across L3-L1 and 50 f across L3-L2. Considering that the 3 hp motor only needs 220 V, I figure I'm OK. The main thing is to not use your L3 leg for any control devices such as relays or transformers. The shematic shown is very stable and is quite commonly used. I added a definte purpose contactor so that there is only very low current running through my start switch. It only grounds the contactor to start the unit. I lucked out and found a great motor on eBay for low cost. If stability and balance are needed for CNC, then I think my unit would suffice.

Inside the electrical box:

http://i144.photobucket.com/albums/r188/gnm109/Machinery/RotaryLayout.jpg

Outside view.

http://i144.photobucket.com/albums/r188/gnm109/Machinery/RotaryPhaseConverter005.jpg

Schematic from Electro Tech Online site:

http://i144.photobucket.com/albums/r188/gnm109/Machinery/RotaryPhaseConverterMiller.png