Converting Bridgeport 408v to 208v?

[MechanoMan]

I have a line on a used Bridgeport Series II for sale we might wanna pick up.

It's wired for 408v 3-ph. We don't have that, nor are we likely to get 408v service. We have 208v 3-ph.

Is the Series II possible to rewire into a 208v 3ph configuration?

I do not know how many HP this one is. I see that some Series II are 2hp, some are 4hp. It is practical to simply replace the motor with a 208v 3ph? If some Series II are 2hp, then even if it's got a 4hp on it now, a 2hp would still be appropriate for what it does, wouldn't it?

Is it always that 408v Series II is going to be 4hp? Seems like there's not a lot of reason to go with such a high voltage for a 2hp drive.

The seller has said the control for feed gears does not work. I'm not clear on what kind of failure that is. Is there some common thing that breaks on the Bridgeport Series II which this might be? This mill has the Acu-Rite head on it, could this be an Acu-Rite problem? How pricey would it be to replace the parts?

[machintek]

Sounds like a S2STD. If so it is 4HP and the motor can be rewired for 220V. There usually is a transformer for control voltage than also can be reconfigured.
The downfeed is a electronic motor unit and probably the board is shot. But there is a small micro switch on top of the quill that sometimes gets its wires cut that could be part of the problem.

George

[ThePrecisionist]

I had a similar problem years ago with a R2E3 we had. It was wired for 208V and we were running 240V.

It kept blowing drive fuses. On a BPT techs advise, we used 2 BUCK/BOOSTING transformers. Solved the problem until we ran the precision out of the machine 10 years later. In my case we BUCKED the power down to 208V. In your case you will BOOST the power to 408V. This is the best way to handle this situation.

I WOULD NOT, try to change the machine wiring. Purchase 2 BUCK/BOOSTING transformers from your local electric supply house. If you can follow a wiring diagram you can wire this tranformer to make the 408. It will be in the area of 30 or so connections you will have to make. between the two transformers. Make up a 3/4" plywood mounting board (ala like an electriction does for a circuit panel.) And use 3/4" EMT to connect the transformers together. Hang on the wall behind the machine. Make all the connections EXCEPT the leads going to the machine. Leave these hanging out in space all isolated. Energize the Transformers. Take your multi tester and check to see you have 408 V (+/- 10%) coming out between any two hot wires. Now you are good to go. De-energize and hook up leads to machine. Opon fire up, quickly check the coolant pump to see if it pumps coolant out. If it does not, switch any one hot wire at the machine to reverse the polariity to the correct direction.

If you can't handle the BUCK/BOOST wiring. Have an Electrician make it for you in his shop. 10 years after making mine, a local shop bought mine for $350.00. So, they are valuable even when you lose the need for use.

One other tip: If you go this route, use the breaker that shuts off power to the Tranformer for the Machine power disconnect switch. This way, you are not transforming power 24/7 365. Only when machine is in use.

Jake

[machintek]

Re reading this is it a 408 or 480 volt machine?
Buck boost are good for going about 10 percent or so.
May be a non USA machine. May need a matching transformer.

George

[ThePrecisionist]

Yes. +/- 10% is correct. But I clearly remember the Magnatek Transformers I bought could be wired for many standard and non-standard volts. This way you could wire the Transformers to the exact volts or to within 10% of where you needed to be. Now, if it's a 50HZ machine....that's another problem.

Jake