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Bob Quale

Plastic
Joined
May 24, 2003
Location
Middletown
My Bridgeport has a three phase transformer that powers the servo motors. In order to make the cnc work with my phase generator i need to get all the controles on single phase. The transformer puts out 70V and 50A. Where can I get such a transformer? Would a 60V be close enough? Input can be 120v or 220v single phase.

Thanks Bob
 
Bob,
Unfortunately I can't answer you directly because I don't have a BPort.... but.... Look carefully at the schematics, or have someone who understands this stuff well look at them. The chances are you will be able to do away with the 3 phase entirely. That is what I did with my Hurco CNC. I figured out the outputs of the transformer and discovered (as I'm sure you will) that the only 3 phase thing in there was the motor. In my case that was being driven through a VFD anyhow. Ironically, on the Hurco control this VFD was also single phase. I dumped the original VFD (Parajust), however, an put in a modern one. Most of these can still be driven single phase though.

The long and the short of it is that after some rewiring I now have a 220V single phase Bridgeport sized CNC mill. I couldn't be happier.

Now the disclaimer.... If you don't know what you are doing then don't try any of this! Get someone to look everything over well and tell you what to do! There are lethal shocks at play here!

Good luck,
Alan
 
I should clarify a bit more....

The manufacturer probably put different single phase things (control, servo amps, etc) on different legs of the 3 phase to balance out the loads. Assuming you know what your are doing, these can be moved around so that they all work off the same 220V input leg. For me that meant getting rid of the isolation transformer.

Alan
 
Wrench

The actual servo transformer is three phase. Three legs in and three legs out. The three out are rectified with a bridge for each of the three legs. I wonder if I can tie two legs together and run it single phase? The schematic makes the transformer look like a delta but no guarantee, or use a step down to 60V? The three phase steps down to 70V. Once rectified the 70V is 100VDC. The 60V is only about 85VDC. Maybe too low. What do you think?

Thanks Bob

[This message has been edited by Bob Quale (edited 06-09-2003).]
 
Hi Bob,
Clearly you know electronics so that is a plus. I'm hesitant to give any advice seeing as this is all off of memory for me. Fundamentally I think you have a valid point, however, if they putting the legs into a full wave rectifier. Clearly their goal is to get DC and DC obviously has no phase associated with it! Sounds kind of strange to me for a brush type amplifier to use three legs in the amp. My conversion was easier. They simply had a single phase transformer, etc, etc. So all I had to do was get each of the different single phase pickoffs all going to the appropriate 220V lines and bingo! I had a machine that was running 220V single phase. As I said, the only tricky part was the GE 3-phase spindle motor, but I just derated a 4HP VFD for that. It all works like a champ now.

I'd hate to give you much more in the way of suggestions on your machine without really being able to look at it with schematics in hand. Sorry.

As for your other question about Mach1. Unfortunately I have no experience with it. I guess my feeling, however, is to use what you've got for awhile until it either breaks or is deficient in some fashion. I have no real need for 3D contouring, so I don't see the push to convert for such functionality.

Alan
 
Most CNC 3 phase tranformer are dry cell. If this is the case with your machine you can still use the transform that is in the machine. All you have to do is remove the wires from the input and output from one cell. Make sure all the componants that need 220 are hook up the the other 2 cells. If you do have 3 phase motor in the machine this WILL burn them up. So please make sure.
Mike
 








 
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