Dumb 3 phase question for BP Discovery 308

[Cellar Dweller]

Dumb 3 phase question for BP Discovery 308

Well, I said it was dumb because I did not do what I should have before we had some work done on our building.

I had my 1996 BP Discovery 308 DX-32 up and running for a while now. Great machine BTW. At least mine is. It is tight and holds tolerance very well. I don’t think it has many hours on it.

Anyway, we disconnected all the machines before the electrician did his work. When he was done, he said he “corrected the 3 phase”. It a “bastard leg service”, (one leg has higher voltage than the other two.)

He said the Phase was not correct. As I understand it the three phases were not in the correct order?? ABC, etc As if it was ACB before he worked on the service.

So my question is, since my machine ran with no problem before the phase was “corrected” do I need to get diagram from someplace as to which leg belongs on which post in the control box on my BP? Was it always hooked up wrong? Or Did we get lucky when we first hooked it up?

We wired it ABC left to right looking into the control box, which matched the ABC in the panel. But apparently, the panel was ACB and not ABC to start with. Why didn’t we have an issue?

The electrician will hook it up, But NOT without a schematic from somebody. Which I can easily do. I need some feedback from the community on this issue. I understand some 3 phase equipment is not sensitive to ABC??

Thanks,
Cellar Dweller

[machintek]

Does your machine have the Siemens spindle drive and axis drives? If so Bridgeport had a service bulletin that these needed a balanced 3 phases (equal voltage). But, in the real world we found that it did not matter. The only devices that were phase sensitive in the 308 machines were the flood coolant pump and the spindle motor fan. The axis and spindle are not phase sensitive (abc vs bac, etc).

George

[jmorris@mailmds]

I would expect the only problem with incorrect phasing is that your spindle motor will turn the wrong direction. If this turns out to be the case, simple swap any two phases at the disconnect and your machine will run like before.

[Cellar Dweller]

To my recollection ( I will double check) my machine does have the Siemens Spindle drive and axis drives.

Gentlemen, Thanks to both of you for helping me out with this. You guys have reinforced my confidence that I won’t have a problem. I will do my best to determine how it was wired for the last 2 years, and replicate that.

My major concern was getting a flurry of responses indicating the machine was phase sensitive.

Thanks,
CD

[EFI-Unlimited]

It seems like most people I talk to don't truly understand how 3-phase power really works.

Most commercial 240v 3-phase transformers on the power pole are wired in what is called a 'Delta' configuration. In the Delta configuration, you will have 4 wires come in from the power pole, 3 'hot' legs and a 'neutral'. If you measure voltage from one hot leg to another, you should have ~240v between all three. If you measure voltage from the neutral to the hot legs, 2 should be ~120v and one should be ~208v. The 208v leg, they usually call the 'high leg'. For a Three phase machine that doesn't reference the neutral line, this doesn't matter. It is only relevant when you are trying to wire up 120v single phase devices.

Having said that, I think you will be fine. Just to be certain, I would put a volt meter between all three phases and confirm they are ~240v.

For more info, see this page
High-leg delta - Wikipedia, the free encyclopedia

Brian

[Cellar Dweller]

Ok, well I hooked up the machine ABC A=122Volts B=214Volts C=122Volts. All was fine for about 2 hours, and then my cabinet lights (They are plugged into the convenience outlets on the side of the control box) went out during a cycle. The cycle never missed a beat, and I shut everything down as soon as the tool came off the part. Knowing I just hooked the machine up to the “fixed” 3 phase, I started checking things.

The 120Volt cabinet lights are toast. Not working.
Then I started checking around with a volt meter and found the following.
140 Volts on one of the pcb. SEE PICTURE. I don’t believe this is correct. Why? Note the picture. The arrow to the left is the fuse housing that services the convenience outlet. Well, it has a 140volts on it? That does not sound right. That is what blew out my lights, I think.

Why would BP design a board to service the convenience outlets and give it a 140Volts????

Also, the smaller of the two large laminated steel core transformers is putting out 140volts??? Why?? It services, the on board pc, monitor, and other items, that to my knowledge a 140volts would damage, at least over time.

I am perplexed and need some help. I can’t understand how come these items have a 140Volts on them. Was it always this way?? Just a coincidence that my cabinet lights stopped working??

Thanks for the feed back,
CD

[EFI-Unlimited]

What do the lines measure between each other? As in A-B, B-C, C-A? That is the voltage that matters.

Brian

[Cellar Dweller]

Brian,
A-C = 247
A-B = 247
C-B = 249

[Cellar Dweller]

All fixed!! After a while of reading schematics and tracing wires I realized that BOTH of the transformers, T1 and T2 were configured for 208. Why, I don’t know. We had an “electrician” (not the same guy who did our recent service upgrade) hook the machine up 2 years ago, and it always ran fine, but the conclusion is it was wired wrong from day one.

A real testament to the electronics and components used. Hard to believe the machine put in 2 years of use with a 140volts feeding the PC, monitor, mag switches, etc But that’s the facts!

We properly configured the transformers for 240 and now we have a spot on 120V coming out of both T1 and T2.

So for those hooking up their machines for the first time, regardless of “who” hooks up your machines, get in there with some reference material and a volt meter. I am very lucky nothing burned out. It’s even quieter because the spindle motor cooling fan is not spinning as fast or Over spinning I should say!! LOL

Thanks to everybody,
CD

[EFI-Unlimited]

Agreed. Being that the input power looks correct, checking the taps on the main transformer was going to be my next recommendation.

Glad you got it handled.

Brian

[jmorris@mailmds]

Sorry to hear about your damage. It sounds like something was not hooked up correctly. Even a "stinger" line will not result in that high of a voltage. I suggest that you ensure the diconnect is open and then make sure that the three line voltages, L12, L13, L23 are relativaly close to 208VAC. As I mentioned previously, phase rotation will simply cause the spindle to turn the wrong direction.

Jon

[ss_again]

My V2XT installation manual suggests putting the "delta" leg at the L1 position. Not sure if it is the same for the 308 but I think they are. There also should be two transformers. Make sure both are changed from 208v to 240v.