1997 Bridgeport Romi CNC flat bed lathe Easy Path S

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Chevy427z
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Re: 1997 Bridgeport Romi CNC flat bed lathe Easy Path S

Post by Chevy427z »

tblough wrote: Fri Jan 21, 2022 11:44 am I've never tried it before, but couldn't you run a 7.5Hp motor with a 5Hp drive. VFD's have a maximum current limit so it would seem that you just wouldn't be able to develop full motor Hp. That way you could get a single phase 5Hp drive and not incur the expense of another motor.
That seems like a very viable option. I've never been one to push any machine to it's limits and as mentioned, this is a garage shop machine and I'll probably never need that kind of power. I would love to be able to eliminate the RPC, though as mentioned, I do have a good one rated at 25HP.

Can y'all make a recommendation for a 5hp VFD for this machine that would be a good match with a Centroid control so I can start narrowing down the decision making process?

I pulled my drive out of the machine today in the hopes of being able to see something obvious, such as burned connections or something. Nothing like that, but I did find the built in cooling fan gummed up and probably not turning on it's own.

Mark
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polaraligned
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Re: 1997 Bridgeport Romi CNC flat bed lathe Easy Path S

Post by polaraligned »

tblough wrote: Fri Jan 21, 2022 11:44 am I've never tried it before, but couldn't you run a 7.5Hp motor with a 5Hp drive. VFD's have a maximum current limit so it would seem that you just wouldn't be able to develop full motor Hp. That way you could get a single phase 5Hp drive and not incur the expense of another motor.
It will work if you set the current limit on the VFD a tad below the max rating (make sure the VFD has programmable current limiting). Problems I potentially see is that the start will have to be ramped slower than with proper size VFD, when taking a cut the spindle speed will slow down if the current limit is reached which could get you into trouble fast, you will be drawing a significant amount of available current just at idle. The lathe is far harder to start and stop than a mill, so I would not choose this route. Plus, the winding resistance of that motor is very low- it might be a pig like my lathe motor.

I personally would get a 3 phase VFD and derate it 50% to run on single phase. There are reasonably priced units out there. Spend the money on the correct VFD and only cry once.
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Re: 1997 Bridgeport Romi CNC flat bed lathe Easy Path S

Post by polaraligned »

How about this 15 hp unit? 47 amp and $800
https://www.wolfautomation.com/ac-drive ... 3-phase-1/

Here is a 20 Hp unit rated 60 amp:
https://www.wolfautomation.com/ac-drive ... ase-33387/ In stock for $649


I didn't spend the time to figure out the difference between them, but the 15 hp unit does take a 10v analog input, I didn't check the 20 hp unit. Call Wolf Automation and confirm with them what you want to do. I don't see why this won't work. Run it on single phase. If I had an extra $800 laying around I would get one for my lathe as I hate hearing that damn rotary converter.
Chevy427z
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Re: 1997 Bridgeport Romi CNC flat bed lathe Easy Path S

Post by Chevy427z »

Thank you for the info Polar! I'll study that closer as I get to that bridge. I am leaning in that direction. Still waiting to hear back from two people who might be able to look at mine first. I haven't had a lot of time to work on it.

I did come up with an idea that I wanted to run by the experts.

I've had this old transformer for 20 some odd years that I bought for a lathe that ran on 480 volts. This bumped up my 220 to 480 perfectly. I've long since sold that machine and the transformer has been sitting around. Since my 220 is running high (260 on one leg) decided to run an experiment. I connected my 220 3-phase to the 230 taps and measured the voltage at the 208 taps. Voltages were well within the range that I need. See my sketch for those. My question is do you think it's safe to run my 230 volt 3 phase machine on this? I've been cautioned to be sure that the transformer is rated for the machine, but I've yet to find a tag on the spindle motor. Does the info the machine tag vs the info on the transformer tag mean anything to you? Thank you!

Side note: I'd love to run the lathe in single phase, but this 25HP RPC is whisper quiet and if I can get my existing VFD working, all the better.

Mark
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cncsnw
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Re: 1997 Bridgeport Romi CNC flat bed lathe Easy Path S

Post by cncsnw »

A 15KVA transformer should be able to carry more than 60A on its 208V taps.

It is unlikely that your machine's total load exceeds 60A.

What you are proposing is to use it as a voltage-bucking auto-transformer. As far as I know (emphasizing that I am NOT an electrician) that should work just fine.

On review, the nameplate says it is an auto-transformer, so it works that way even when you are using it to step 480V to 240V or vice versa. So you are proposing to use the transformer as it is designed to be used.
Chevy427z
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Re: 1997 Bridgeport Romi CNC flat bed lathe Easy Path S

Post by Chevy427z »

cncsnw wrote: Sat Feb 05, 2022 4:06 pm
On review, the nameplate says it is an auto-transformer, so it works that way even when you are using it to step 480V to 240V or vice versa. So you are proposing to use the transformer as it is designed to be used.
Wonderful news. Thank you very much!

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Chevy427z
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Re: 1997 Bridgeport Romi CNC flat bed lathe Easy Path S

Post by Chevy427z »

Finally heard back from the VFD repair guys and as expected, it's too costly to fix. $1600.

I contacted Wolf Automation, as suggested by Polar, by submitting a request for quote from their website. They recommended a Teco Westinghouse 3 phase at $550. I am happy with that price. I had hoped to talk to someone to discuss the possibility of running a single phase unit. Hoping to get a response from you guys before I call them on Monday.

Is there a quick answer to "which is better?" Is the only benefit to running single phase not having to listen to the rotary phase converter running constantly? That's not a huge issue to me as I already run one for other machines in the shop and I don't even hear it after a while.

Thanks again for your guidance folks! One step closer.

Mark
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Chevy427z
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Re: 1997 Bridgeport Romi CNC flat bed lathe Easy Path S

Post by Chevy427z »

I went ahead and ordered the Teco Westinghouse 3 phase at $550.

He explained to me, as Polar had tried to earlier in this thread that I *could* run the lathe on single phase 220, but that I'd have to upsize the VFD to twice the capacity. My machine is 7.5 HP, it would have to be sized to 15.

Onward and upward.

Mark

Edited: Wouldn't ya know it. It was in stock all the while we were discussing and the moment I gave them my CC info it went out of stock. Expecting replenished stock at the end of April. Glad I'm not in a rush. This will give me time to read the 500 page manual to better understand it.
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Chevy427z
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Re: 1997 Bridgeport Romi CNC flat bed lathe Easy Path S

Post by Chevy427z »

I couldn't find a "proper" place to ask this, so I'll ask here.

I have email notifications checked for the various options in my profile, if someone replies to my post, if someone quotes me, etc... but I never get a notification. Can anyone explain what I am missing or doing wrong? Thanks!

Mark
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Chevy427z
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Re: 1997 Bridgeport Romi CNC flat bed lathe Easy Path S

Post by Chevy427z »

Hi folks.

I am finally in a position to start buying the parts I need to do this retrofit.

I've been in contact with sales to get a quote, but they suggested that I make sure that my servo drives are compatible, and that the pinouts are correct. I have been reading, and reading, and reading, and looking at the install manual and schematics and without all the parts in front of me I get very confused. I am hoping to get some guidance in ordering the right parts so I can just sit down and start installing things to make better sense of it.

At Polar's suggestion, I've purchased a Teco Westinghouse E510 spindle drive from Wolf Automation. That was $550 vs $1600 to repair my original.

I am looking at Centroid's Touch Screen Console (#13181), the OAK Board (#13135), and drive cables - for Yaskawa Sigma (#13134). I'm thinking that I don't really need an MPG with this installation as X and Z on the machine should perform that role.

So, what do you think? Will that get me started?

Mark
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X axis servo motor 2.jpg
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