MIMF

I acquired a nice Harrison steel lathe this week(new toy! <bg>), and other than still trying to find the best way to move the 1600+ lb beast -into- the shop, I also have to change the motor, as it is equipped with a 3 phase, 550 volt motor right now. Question is, what's the equivalent 110/120v motor, in amps, please? the 3ph/550 motor is rated at 1.67 amps, which looks to be about 1 to 1-1/2hp. But today's motor horsepower ratings are so skewed, I ignore all hp numbers and only go by the motors' amp ratings when comparing. I know that a 220/240v motor pulls half the amps that it would at 110/120v, but can't remember if the amp draw drop is linear or what as we continue upward in voltages, as well as 3phase VS single phase, and whether or not that makes a difference in actual motor HP. Since I need to find or buy a motor for this thing, I'd rather get the right one the first time....

thanks!

That's roughly a 2+ HP motor..... appx 1600 W.
You'll need a 3ph 230V at appx 4.5A, or just around 8A for a single phase.
What about a VFD, single phase feed and 3-ph output....? A 2kW VFD would be just about right...

Thanks! You confirmed my math, as I calculated I will need a motor rated at 8.3 amps at 110v, which here is about a 1/2 HP motor. Why do you think the existing one is around 2HP? A 1/2 HP motor does seem small for this size lathe(it's a Harrison M250; 11" swing, 30" bed), which is why I'm second-guessing my math.

I'd rather not bring any transformers into my shop; they take-up space(of which I'm running out of!), create heat and I've never met one that didn't hum.... besides, motors are cheaper and easier to find. Once I know for sure what I need, I'll put the 3ph motor up for sale or swap on the local swap lists in hopes that someone can simply swap the motor I need for the one I don't... <g>

You have to correct for 3-phase by multiplying by sqr(3)= ~ 1.73......
So 550V x 1.67A x 1.73 =1589W........ or roughly 2+ HP of power drawn...... not delivered on axis....

Whoa! If you're correct, and I think you are now that I've read-up further, then I need a minimum 7.2 amp/220v motor to replace the 3phase one. THAT will cost more than anticipated..... And now the VFD you mentioned begins to make more cost-sense(and having read-up a bit on them just now, I also see they are not transformers or anything like that).

Can you elaborate further on the 2kw FVD, please? Will I get the same power(HP/torque) from the motor, or is there a loss? I appear to be getting conflicting information in my early reading on the subject.

Thanks!

You could also probably get a rotary phase converter if swapping the motor becomes more of a hassle, but they're not the cheapest...

I do have some experience with VFDs, as I have used them for test rigs where we needed vairable speed. In theory, they should give full torque at any speed, but guess that is a truth with some mod's to it, even if this is where they really excel. I also notice they are used more and more as 3 phase converters, where 3-phase is not available.
The US / Canadian markets in this context is somewhat obscure to me, as a european, where most machinery is either 230V or 400V for heavier stuff. Whether direc conversion from 220V single phas to 550V 3-phase could be available, I don't know, but I doubt is. Usually it is the same or lower voltage out with respect to input voltage.
Since metal lathes already have gearboxes, you really don't need the variable speed, so I thought oof it more as an easy fix for 3-phase, if you don't already have that in your shop.

230V single phase motors up to 2.5-3 kW are fairly common around here, and a 2kW new one, probably of eastern make,are around 300USD over here. They should be rather cheaper over by you, I guess, and it also seems that you have a rather extensive market for used stuff.

EDIT: Sorry for the typo's --- seems my laptop needs a new keyboard...

Thanks for all the help; I have a few friends nearby who are industrial electricians who could help me out, I'm sure, but none of them are on-line... <bg> Correct that I don't need variable speed, and I also wondered how it could/would step-up the voltage from 220 to 550. So that puts me back at buying a new 110/220 single phase motor, which should be about $200/$250 around here. Problem is, this lathe ate all(and more) of my "play" money, as it was a last-minute, unexpected opportunity that just dropped into my lap and I couldn't pass it up! In other words, I'm cash-poor right now.... <sigh> Ah well.

Just curious. I have never before heard of a 550v 3 phase system. Is this something common in the US? Industrial?

In Europe we used to have 380v as 3 phase but I believe it is now standardized on 400v.

There are a lot of folks who use VFDs on their CNC machines, and they all take 220V-1 phase and convert to 3 phase. I don't belive they put out full torque at any speed; rather they pump as much juice as needed to maintain a certain speed, within a certain percentage.

This is one maker of a widely used VFD. I'vev seen 480V output VFDs so I'm sure they have higher-rated ones. If I'm not mistaken, you could use a VFD with a lower HP rating, but then you limit the motor to that lower HP.

I think however that swapping motors might be the cheaper of the other alternatives. A VFD with a 4kW rating is not cheap, neither is a rotary phase converter. You could find cheap Chinese VFDs on eBay, but the documentation can be poor (unless you can read Mandarin!) I have a 4HP VFD that I'm using for a CNC mill, and was fortunate that a member at the CNC Zone had a girlfriend that was studying Mandarin, and translated all 72 PAGES of the manual! Completely nuts! Haven't fired it up yet, but resources like that are priceless!

http://www.delta.com.tw/product/em/driv ... r_main.asp

Congrats -- that's a very nice lathe! Hardened ways, camlock chuck, big spindle bore... I wouldn't pass that one up, either!

Yes, Halgier is correct on the power factor correction for 3-phase. The rated power is probably around 1.7 HP, which is very reasonable for 11" swing, but you could probably get away with quite a bit less, depending on your depth-of-cut, feed, SFM, and material. Older US lathes of that size would usually ship with 3/4 HP motors, which is reasonable for the limits of a HSS bit. To hog off stainless (using carbide), may need more than 2 HP.

Motor/drive selection for a metal-cutting lathe is pretty complex and interesting. Some miscellaneous thoughts, which you may know already...

I don't know of any reasonable way to run a 550V motor off of a 220V circuit. Except for a few tiny 1/2 HP units, VFDs have the same rated in-out voltage. I suppose a custom 550V RPC could work, but that would be much more $ than a new motor.

I'd agree variable speed is nice, and also that it's not a requirement.

I've never tested it back-to-back, but many machinists say a 3-phase motor gives better surface finish than a single-phase motor, as it delivers the power more smoothly. Other machinists haven't seen the effect. Here's one good discussion:
http://www.practicalmachinist.com/vb/ge ... he-150022/

A DC motor is also good for surface finish. I put a 2 HP DC motor and regenerative drive on an 11" Logan a while back... cost me around $100 (+ time):
http://malicky.com/davidm/my.projects/my.projects.html

Amps aren't the best to compare motors, as efficiencies vary. With the nameplate HP, SF, and duty, decent HP comparisons can usually be made (cheap asian motors excepted).

Using a big chuck with a tall gear, the motor will see a high startup inertia. So if using a single-phase motor, it would need to be capacitor-start, or better, capacitor-start capacitor-run.

The lowest $ single-phase motors I've found are used pool/spa pump motors. Typically capacitor-start and <$50 for 1-2 HP on craigslist. I did a little writeup here:
http://luthiersforum.com/forum/viewtopi ... 4&#p462354

3-phase + VFD could probably be done for <$200 if you don't mind hunting. Let me know if you want to go 3-phase or DC for the surface finish... I can give more info on those routes.

Thanks for the extra info, David. Right now, I have another home machinist who's willing to swap me an older 1HP 110/220v motor for my 3ph one. Straight-up trade. He says it came off a vertical mill, and he was keeping it as a spare for his own vertical mill, but since his mill is already 3phase, he can use mine as his spare. It's a 100+ mile round trip, and we had freezing rain overnight and a couple inches of snow this morning, so this may prove to be one of my more, uh, "interesting" mornings .... I'm not overly concerned with surface finish; that's what tool post grinders are for, anyhow. I'm also more than willing at this point to reduce the initial gearing if I need more torque than the swap motor can supply, and I don't foresee cutting large-diameter SS any time soon(but one never knows... ) I'll keep y'all posted as to how I make out today!

Correct on the lathe; it's a sweetheart! Can't wait to get it into the shop, and up and running. I'd never seen a camlock chuck until now; it came with a 3 jaw, a completely unused 4 jaw, as well as two face plates! The only disappointment so far was finding out that it doesn't have a clutch and brake, which would be very handy to have if I get into making bridge and end pins(as well as the brake being a good safety device!), but hey, once I have it running, I should be able to rectify that little oversight of theirs'. It was a CNC/manual lathe, too, so another of my first tasks will be to turn a short shaft so I can get rid of the motor on the cross-slide, as right now you literally crank the motor to move the slide manually. Ain't it fun to have tools that literally build other tools for themselves? Spent the first week with it literally removing all that late 80's technology from it. It's crazy where we've come from in 20 years.... It used a cassette tape player as a data storage/transfer/drive! I have more computing power in my little wee Blackberry than it had in the 700lbs of electronics!

That sounds like a great trade. 1 HP should be plenty, even at higher speeds. Hope the drive wasn't *too* interesting.

Great to have the chucks and faceplates -- as you know, tooling $ can kill the budget. I bet they are good quality, given the lathe maker. The camlock mount is remarkable, especially how the taper and face both get engaged simultaneously. There must be some super tight tolerances for those surfaces. Mounting one is somewhat tricky to get concentric -- progressive tightening is the key (the Grizzly instructions are actually very good). Mounting a chuck that's never been mounted can be more tricky, as the studs may need adjustment and the surfaces usually need to become acquainted a few times. 0.0005" TIR should be achievable after a half dozen mountings.

If a mechanical brake is difficult to implement on it, DC and 3PH-VFD can both be braked with resistors. Yup, nothing like a lathe to replicate tools! I know what you mean on those old CNC electronics, or I should say, the new electronics.

Turned out to be an even better deal... When I got there, the fella looked at the plate and realized my motor wasn't any good for him, as it was a 550-575v, and he hadn't noticed that in my ad. BUT! He pointed to his motor on the bench, and said "go ahead and take it with you anyhow; I'll never use it". Woohoo! There ARE still some fine folks in this world! Ended up spending about 30 min. to an hour in his little hobby machine shop, talking shop. He's got a real, real nice setup! Calls it his "mid life crisis"... He also had a VFD and showed me how it worked. Nice! But he didn't think it could bump 220v single phase to 550v. All of his machines are 3ph, 220v.

Now, maybe you can help me out, further. The 1hp is an older GE, and looks and feels solid, but the wiring diagram has peeled away and left this earth a long time ago, so I don't know if it was setup for 110 or 220! I'm pretty sure that we can run a 220-wired motor on 110 without damaging it(though it will only have 1/4 of the HP), so I wired it up with a temporary plug, and gave it a shot. The rotation is correct for the lathe, and comparing it to another 1750 RPM motor, it appears to be running at full song. But it also appears to start somewhat softly. yes, even clamped down with one clamp, it rears-up a little on initial startup, but I would expect more from a 13amp motor.

How can I tell if it's setup for 110 or 220? I have a multi-meter, but other than reading voltage, I have no clue how to do anything else with it... <sigh> I suppose if it's okay to run it on 110, I'll know right away when I put a load to it, right? A 1/4hp motor won't do much when the cutter takes to a steel shaft, where the full 1hp should laugh at everything but the craziest hogging-off of material. What do you think? I still have a couple of days before I will have the lathe -inside- the shop, so there's no rush.

Mario Proulx wrote:Spent the first week with it literally removing all that late 80's technology from it. It's crazy where we've come from in 20 years.... It used a cassette tape player as a data storage/transfer/drive! I have more computing power in my little wee Blackberry than it had in the 700lbs of electronics!

Before you do anything you regret...depending on the motors, you might be able to set it up as a modern CNC lathe for a few hundred bucks, though software will add a bit to that. It would make turning bridge pins a breeze.

Andy Birko wrote:

Mario Proulx wrote:Spent the first week with it literally removing all that late 80's technology from it. It's crazy where we've come from in 20 years.... It used a cassette tape player as a data storage/transfer/drive! I have more computing power in my little wee Blackberry than it had in the 700lbs of electronics!

Before you do anything you regret...depending on the motors, you might be able to set it up as a modern CNC lathe for a few hundred bucks, though software will add a bit to that. It would make turning bridge pins a breeze.

LOL Mario is not a CNC type of guy! But I guess the machine is not "that" old... otherwise it would have a punchcard slot!

I've been around machine tools all of my working career and I've never heard of one type of motor making a better finish than another. Is that some kind of old wives tale?

The school looked into having it converted, and it was well over 3 grand. And of course, I'm not a CNC guy, anyhow.... There's nothing CNC can do with a lathe that would be an advantage to me, since here, it is a tool to refine/repair my other tools, and make the odd part here and there. Even if I got into bridge and end pin production, CNC would be of no use there.

I decided to fast-track getting the lathe from my garage, and into my shop, this evening. I found the ways had begun to stain, so rust wasn't far away. It's in the mid 20°F's here right now. So, I cut an opening in the wall between the shop and garage(where there's a beam and chain hoist that helped me unload the beast from my truck), and "walked" it into the shop with some 1/2" pipe as rollers. 2 hours into it, I had the lathe inside the shop..... Spent the next hour wiping it down, cleaning it with naphtha and oiling any and all exposed surfaces as it was sweating like a petty thief at the copshop.....

Nelson Palen wrote:I've been around machine tools all of my working career and I've never heard of one type of motor making a better finish than another. Is that some kind of old wives tale?

It's a good question. I've not seen any scientific studies on it, but there is a physical basis for it being real, and many reports of people having finish problems with single-phase that went away after switching to 3-phase, or rubber-isolating the single-phase motor more effectively.

A very rough analogy is a 1 cylinder vs. 3 cylinder IC engine. More accurately, a single-phase motor produces ~zero torque twice in 1/60 of a second (or 1/50 of a second for 50 Hz). So, that motor is shaking the machine at 120 Hz through 2 paths: the belt and the motor mounts. Either or both of those can setup a small vibration problem in the machine that resembles mild chatter. Many single-phase lathes may not show the problem, if the motor has good rubber mounts and the belt is long and not too tight, or if the lathe has a lot of rotational inertia (big chuck), or if it just isn't sensitive to 120 Hz vibration. But other machines apparently do show the problem. A 3-phase motor produces 3 staggered torque pulses that overlap and add up to be much smoother. There is still shaking, but it's much less severe since the torque never drops to ~0. See the last page of this doc for a figure of this torque ripple: http://powerelectronics.com/mag/608PET20.pdf

In most larger shops/factories, lathes are generally 3-phase since 3-phase power is available and 3-phase motors are simpler, more reliable, and less $. So most machinists may never run into it, making it an irrelevant issue. That's actually the preferred case.

Here are some threads discussing it...
http://www.practicalmachinist.com/vb/ge ... ors-72372/
http://www.practicalmachinist.com/vb/tr ... se-101879/
http://www.practicalmachinist.com/vb/gr ... ts-110628/
http://www.practicalmachinist.com/vb/tr ... or-102776/
http://www.practicalmachinist.com/vb/ge ... on-153809/
http://www.practicalmachinist.com/vb/so ... dc-226431/

Nice lathe, and lathe-doorway! Congrats on getting it ~rolled in. Yeah, I bet it was sweating. That's a fine fellow indeed... it's always fun to see someone else's setup.

Is there a Z-axis motor for the CNC? Or did it simply rely on the geared auto-feed?

I'm not sure if a 220V wired motor can be safely run on 110V. Maybe Halgier can give input. In general, a motor seeing low line voltage will draw more current under load, and could overheat. But without load, it should draw less current as the winding resistance is higher. That's basically the difference in wiring it for 110 vs 220: for 110, windings are wired in parallel; for 220, in series. Parallel windings have less resistance, so more current can flow to make up for the lower voltage. Either way, each individual winding sees 110V.

Does the motor have 0, 1, or 2 capacitors? Also does it have a centrifugal switch? If 1 and yes, it's capacitor-start, and diagrams are readily available. Here are some good links on single-phase dual-voltage motor wiring (note the 2 types of start windings)...
Page 8 and 9 are the standard NEMA capacitor-start wiring diagrams: http://www.goevans.com/EHB_pgs0803.pdf
http://www.hvactroubleshootingguides.co ... motor.html
Can you take a pic of the motor junction box showing the terminals and wire colors? If it follows the NEMA standard wire colors and/or numbers, the wiring can be deduced by seeing how the colors/numbers are grouped on the terminal blocks. If that doesn't work, then winding resistances can be measured to figure it out, but that's a lot harder.