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Lathe - Phase Converter

  
 

 

 
 
Problems with my phase converter (Nov 15, 2001) Rotary Phase Converters (Aug 12, 2004)
Rotary Phase converter (May 15, 2003) New Motor? Rotary 3 phase converter (Dec 15, 2004)
Phase converter 3 phase vs. single phase (May 17, 2003) Rewire for 1hp 110v. Phase converter (Jan 4, 2005)
Phase converter experiment/questions (May 23, 2003) Phase converter (Mar 12, 2005)
Phase Converters (Jul 22, 2004) Phase converters - Instant reverse (Mar 13, 2005)
 
Problems with my phase converter
Does any one on the list have experience running three-phase tools on single-phase power? I have a new/old SB Heavy Ten that I just got set up to use (about 16" between centers). It has a three-phase motor; a relative who is an electrician made a device for me so that I could use single-phase 240V power to run it. It has two switches; one marked "start" and the other "run." The first time I ran the lathe I forgot to turn the start switch to the "off" position as soon as it ran up to speed. (Like the greenhorn I am I got excited and lost track of all the things I was supposed to keep track of.) I realized my mistake only after a couple of minutes. Now the lathe won't start. I took one of the capacitors out, assuming that it had burned out, but a fellow at an electric parts distributor tested it for me and said it was fine ("I've got bad news for you - you don't need a new one of these"). Are there any other capacitors, in the motor for instance? Any other suggestions (besides buying a single-phase motor for the lathe)? E. Grim (2168)
Sounds like he wired the start capacitor in with its own switch. Which is fine, but he should have used a momentary push button so once you let go, it would take the start cap out of the circuit. The cap you burnt up is the round electrolytic start capacitor. Has a bakelite case. Don't be embarrassed, call your friend tell him whatcha done, ask him to bring another start capacitor and a momentary switch to replace that toggle switch. Marty (2172)
Sounds like you have a 'static phase converter' which is really just a start capacitor. You might check both switches for continuity. also consider using a pushbutton for the start. Then check the three wires to the motor - resistance should be similar between any two pairs. Check the lathe's power switch Check the fuse. The best way to do this is to buy a device called a VFD which will synthesize 3 phase power at variable frequencies, which gives you variable speeds, too. You need to get one rated for a larger motor than you have to run it off single phase. Chris (2173)
Rotary Phase converter
I am going to build a rotary phase converter, my question is, I will use a 5 HP 3 Ph motor as the converters starter motor, it is only a 1140 RPM motor, is this OK to use as the starter motor? to run my 1740 RPM motors? Clint (11136)
I just got through picking the brain of the guy that owns convert a phase. He said the most important thing with a home built phase converter is to get as big a motor as possible. Not HP wise but size in general because it will hold a better magnetic field and take your motor starting with ease. as for the rpm it doesn't matter you have 60HZ coming in and you will have 60HZ coming out and the third phase will be generated so RPM doesn't matter. Kerry (11140)
Kerry, it is the common consensus that the induced 3rd phase will be smoother with a 3450 rpm motor because of more revolutions per phase?? Here is an excellent way to build a "home brew" rotophase. (commercial rotatory phase converter) www.frugalmachinist.com/rpc.html  and www.metalwebnews.com/howto/ph-conv/ph-conv.html  archie (11143)
IMO and not afraid to admit being wrong (sometimes) Nop not exactly. You don't get more revs per phase. The distance traveled is still the same 1/3 of a rotation or 120 degrees per phase it just gets there twice as fast what does happen is the windings on the armature are set up to move half as far in rotation before the get another push to complete the rotation. A slow RPM motor is coming in and out of flux slower then a fast RPM motor. But the motor is still putting out 60Hz or there about, so I'm not sure what you mean by smoother. I do know that if you can find a motor with the windings parallel with the shaft you will have a much more efficient generation of the third leg almost all motors are wound with the windings in a helix around the shaft to generate more torque. But in a phase converter there is little load on the motor so torque is not really needed. I would like to know more about it. I could go listen to the guy that builds these things for hours. Kerry (11156)
From what all I found out today is that it really make no difference to the RPM, especially using the converter for hobby work Clint (11159)
That's what I thought. But will stand corrected if wrong. At least if it was not as good as a 3400 RPM motor this will get you on your way till you could get one. But it's not needed. My AC drive will be here on Tuesday and I picked up a 3000 watt transformer from a surplus yard/ toy store. $40 latter I have 230VAC and more capacity then the 110 line can supply. I'll never overload the transformer. can wait to get it running. Makes you wonder though... if three phase is more efficient, the motors are cheaper and simpler. Why is my house and everything else not wired for three phase? and a lot of industrial buildings don't have three phase either. I understand that every electric motor in the home is single phase and would be hell for a change over. but it just doesn't make sense to me. Kerry (11160)
Kerry Now all I have to do is find the stuff to make my own panel of start capacitors, etc. and then I will be ready. i really do not need this but since I do have a couple of 3 ph motors and doing this lets me use the original SB motor on my 9" lathe and the controls. Right now I am running a single phase on it. Clint (11161)
Sort of like Macintosh vs PC. Better systems don't necessarily make it. There's a story that Steve Jobs once told Bill Gates that he thought it was idiotic that the PC, far inferior to the Mac, took over the world. Gates just smiled and said "Steve, you just don't get it, do you?" A similar thing happened with video systems But SB rules! Frank (11162)
Probably just a matter of infrastructure. Looking at the wires going by, out my window, I see that there is no 3 Phase here. So it is not just a matter of house wiring...someone would have to spend a lot of money, from the nearest substation to the street, and replace the pole transformers, etc. I did formerly live in a town that had its own little municipal electric plant. They required anything over 5 HP to be 3 Phase, and in particular, air compressors that stared under load. Starting surges per leg were a lot less with 3 Phase, as well a running current per leg. In single phase, when the voltage reverses, the wires are doing nothing for a few degrees, whereas in 3 Phase, one phase or another is always conducting. (11163)
There has got to be a surplus yard or electrical junkyard near you or some where around not too far. I'm lucky to have a guy that owns a yard and builds phase converters 5 minutes from my place, so not only do I have parts I have a brain to pick as well. I love electricity, I has so many properties that you have to pay attention to. Magnetic currents, lines of flux, It's nice to build something that would just stump and average guy. If you need any thing out of the ordinary let me know I could take a look and let you know what he's got. Kerry (11164)
Phase converter 3 phase vs. single phase
"Kerry" ... many things do not require 3 phase so if you used 3 phase, every house would need a 3 phase circuit and a single phase circuit. And not every house has requirements for 3 phase. The motors in the house, fridge, washer, dish washer, dryer, furnace, pump would all benefit from a 3 phase line, but then the electrical switches create another problem/expense. a 3 phase motor has 3 contacts vs. a single contact for 3 phase. 3 phase circuit breakers are much more complicated too. From a viewpoint of simplicity and cost, everyone needs single phase. But if you want to talk economics, 230 if usually more efficient than 110. Europe uses 220, and the US uses 110? go figure. Dave (11166)
Dave, If I understand 3 phase, there are three single phase circuits; each having their individual phases spaced (timed) 120 degrees from one another. Therefore, the voltages phase-to-phase are 208V rms. but the voltages from phase-to-neutral are 115V rms. As I see it, the problem with using 3 phase in residential wiring is the balancing the single phase loads across the three phase input. This could be done but it complicates the wiring and increases the costs. Of course, you lose a 230V rms. single phase circuit. As to rota-phase converters, they never give true three phase output. The spacing of the phases are not 120 degrees apart and therefore you cannot get full output of your three phase powered machinery. The output of your three phase equipment using a rota-phase is by "rule-of-thumb" about 1/2 to 2/3 of rated HP. This generally isn't a problem for most hobby and light industrial use. Just something to keep in mind. If you want true three phase, get a VFD. You also get a lot more this way too (i.e. variable speed). Webb (11170)
I beg to differ but you'll get better three phase from a rotary converter then an AC drive. AC drives convert the input to DC then run it through a series of transistors to switch the power direction and frequency. This is why AC drives are not to be run on sensitive equipment and can't be used on CNC machines due to the RF signal they generate. Unless you're talking inverter drives the high dollar ones the power you get from a AC drive is not very good compared to a rotary phase converter And a Rotary phase converter will generate a good enough Third phase to get full horse power from your motor as long as the idler motor is big enough to supply the current. You are thinking static converters that run your machine on three phase to start it then one phase drops off to run it. and this is why you can only get 2/3 the HP from it. You are right in the fact that the it doesn't produce "true" three phase power. Neither does a AC drive or an Inverter then trick the motor in thinking it has three phase by producing power that is close enough to "true" three phase The only way you can get "true" three phase is to get it from the utility company. What do you mean "light industrial" I have a very good friend that has a full machine shop on his large lot with his house. It's about the size of a three car garage. No three phase and he runs three CNC Machines a manual lathe and mill plus all his wood working tools, All on three rotary phase converters that are UL listed and rated to produce more power then he needs and he ain't "light industrial" One runs his VF3 HAAS the others run his chevalier, dynapath machines, wood working tools and manual machines. They can run at full HP and up to 130% more if needed on the HAAS about 115% to 120% on the others. This is a known fact tested by the HAAS reps and my buddy. I don't mean to slam anyone but please get he facts straight first. Kerry (11171)
Thanks for the comments on the Phase converter, I am all set on how to go about it, all I need now is the supplies to build the panel. Clint (11172)
I wish I knew more about them, but on the surface I would tend to agree with you. On the CCED list they recommend using a 150% rating for a VSD and from what I have seen you need to do the same on a rotary phase converter. My local shop has a rotary 5 hp phase converter on his 3 hp lathe and since he moved from a true 3 phase from the power company he has noticed a very significant loss in power. There are a lot of guys who use VSD's on the CNC stuff and some CNC software will regulate speed for threading and such. But, the advantages of 3 phase remain. Dave (11177)
Kerry, Obviously we have a difference of opinion. Rota-phase converters generally do not have balanced 3 phase output. And if the three phases are not balanced, you cannot get full HP from your motors. Published recommendations are that the first motor run (no counting the spinner) will have only 60% or less of its output. As one adds more motors to the circuit, the efficiency goes up but motors should never be run above 80% of their 3 phase rating. VFD's will give the proper balance but not a smooth sine wave output (more of a "stair step"). Some people add "chokes" (copper wire wrapped around a steel donut) to handle voltage transients with VFD's. As to my definition of "light industrial," I refer to shops that are using equipment with motors of 10HP or less and don't usually have more than 10 pieces of equipment running at any one time. (11186)
Well from the guy I know that builds them for a living and every other company that makes a Rotary Phase converter they all claim the same thing 100% full HP as stated on the name plate of the driven motor so long as the converter is able to supply power. This is from Phasemaster Do I lose power or capacity when I run my equipment on a phase converter? For rotary phase converters, the answer is a resounding "No!" Provided the converter is large enough, a rotary phase converter will develop the entire nameplate horsepower of the motor. You will have no power or capacity loss at all on a rotary phase converter. The same cannot be said for static converters, which generally do not allow motors to develop full horsepower. Static converters are unable to balance a current into three different legs. Once a static converter starts the motor, it switches off the line and the motor actually "single-phases" one winding carries most of the load. Once that winding reaches its full capacity, that's all the load the motor can carry without tripping off or burning up. This usually occurs at between 60-80% of the nameplate horsepower. This is why static converters are only recommended for small-horsepower, single-motor applications. So once again I believe you are talking about a static converter. Yes I understand if the load is not balanced one the two legs coming in there will be a dip in the HP. But that applies to everything that is run out of your power panel so to me you're splitting hairs. Why would a company make a bold statement like that and leave no doubt as to what they mean? They would be shot down and sued for false advertising. Why haven't more people like your self contacted these companies to force them to retract these statements? Why does the Metal Web News say they exact opposite you do? I admit I don't know everything about electricity or electronics. That being said though I feel I can trust the companies I deal with and the people I know personally not to lie to me. Show me these "published recommendations" you talk about. I can't find it. Kerry (11192)
Kerry I am just now getting into learning about Static and Rotary Phase converters, and so far, what you are saying here is what I have found also. Chipmaker (Frugal Machinist) http://www.frugalmachinist.com built his own and tells me he is getting full power, the same info I am getting from the phase converter builders and others that run them Now the Static Converter is fine if a person can stand to loose a 1/3 of the HP. Clint (11200)
Clint Perfect you are looking and researching for yourself and are finding exactly what I have found that a Rotary phase converter will provide full amp load to a motor running at full capacity. And the only ones that don't provide full power are the static versions. Webb Boy We aren't talking true three phase. we know that static boxes, rotary converters, AC drives, and inverters DO NOT produce TRUE three phase. I stated that about a dozen posts ago when I said it tricked the motor into thinking it's getting 3PH power. we're not talking about that. We're talking what the converter produces in terms of usable power. everything I can find on the web and from talking to my buddy say's that even a home built rotary phase converter will provide full load amp if properly selected or built. I don't care what the damn wave form looks like as long as the motor is pulling the amps and producing the HP I couldn't care less if it looked like a spiral stair case. The FACT is a rotary phase converter is able to supply full load power (amps) to the motor Period. There is nothing that I can find anywhere that say's anything about a ROTARY PHASE CONVERTER not being able to generate full HP in a motor. Like is said you are splitting hairs. If I wanted to split hairs I would say that I need to convert 114VAC to 228VAC then to 3PH. Now what is it 110VAC or 120VAC well it doesn't matter because most everything electric can handle a deviation in power to some degree. Uhmmm you ask if he's hooked up an O scope. Yep and there are test reports ON FILE with Underwriters Lab. His converters were the first to get UL certs. Now I'm still waiting on these "published recommendations" that you claim to have read or otherwise known about that allegedly state a Rotary converter will at best produces 60% of the full power needed to run a motor. So where is it? Or is it just time to put the boots on and clime out of the BS you've been spewing on this board. To anyone that I may have offended other than Webb boy, I apologize. But we are here to learn from each other and each others trials and errors. Others have written in and been wrong but mistakenly so. They have withdrawn their statement, admitted to being wrong or mistaken and we all learned from it and moved on. I guess I should have dropped this a while back but damn it I'm not going to sit here a listen to some moron mislead, misunderstand or just plain lie to use. Clint has looked for himself and can only find info in direct conflict with the postings of webb boy. I'm not going to speak for Clint, He is quite capable of speaking for himself. He has corrected me once or twice but he wanted to know for himself and was not about to take either one of our words for it. So he did and posted his findings. I'm done My point has been driven into the ground and the horse is dead and beaten enough. Thanks And I do apologize Kerry (11209)
Kerry/Webb and others I have pretty much made up my mind on how I plan to go. For Hobby lathes/Mills I think that a rotary converter is fine, as well in a lot of cases a static converter would be OK also, for instance, For a 9" lathe, a 1/2HP motor is plenty for Home hobby work, etc. so if I had a 1 or 1 1/2 HP 3 phase motor, a static converter would provide plenty of power, now if I needed 1/2 HP and only had a 1/2 HP motor then a static converter would be out of the question Then a Rotary converter would be proper. Of course it is probably much easier and cheaper to just install a 1/2 HP 110 V motor. I have plenty of 110 V motors but I do have the original SB motor which is 3 phase and would like to use it. and I also have several other 3 phase motors I can use for my shaper another SB lathe and so on. I do not have to but my nature of challenges leads me in the direction of using them just to do it! if i had a large shop with loads of equipment with 3 phase motors, etc. and it were a production environment, then all things considered I would probably be a lot more concerned with the most accurate methods of powering the 3 phase. Any how, all the info I have received has been very helpful to the fullest and served the purpose of the group thanks very much guys Now we can go on and come up with some other great ideas for our machines and hobbies. Clint (11211)
Well said. I hear you about the challenge. It's nice to that you did it, you did it yourself, and you didn't let it stop you. It feels good at the end of the day. Once they're converted to three phase they will run smoother draw less amps and are much cheaper if they should need to be replaced. But you already knew that. I wish I had the amps to run a rotary converter. But with only 15 to 20 amp 110VAC coming in I think I would be pushing my luck with a 3HP mill. So I have an AC drive coming in tomorrow. I already have the transformer 3KVA and about 30# of copper. I should have it up and running this week. the first thing I'm goona do is throw it in reverse and see if I trip the breaker. Then I'll take a good cut and see if the lights go dim. I don't think I'll have any problems, I made some test cuts at work with an amp meter hooked up and the same machine with the motor uses 3.5 amp @ 220 3PH under no load and then only goes up to 4 amps with a 3/4" four flute end mill in tool steel .25" depth of cut and feed in until I hear the motor start to load up. and for us at work that pushing it. I was surprised that what we though was really pushing the machine hard was only using 1/3 of the rated HP. The machine still had a lot of steam left. Kerry (11214)
Some people have to resort to belittling and name calling in order to put forth their opinions. I thought that most of us had better sense than to believe everything a piece of sales literature states. It is possible for a rota-phase to put out relatively good balance at a specific load if it have been tuned to that specific load and the power and the power factor will be pretty good. In a shop that has a variable load (i.e. different machines being turned off and on and different times) the balance will vary accordingly. For those who doubt my veracity, I have attached one published article that I was using as the basis for my comments. As far as being registered with Underwriters Laboratories (UL), all that means is that the product is safe to use as long as it is used in accordance with the manufacturer's instructions and recommendations. It does not certify that it does what it claims. As to "tricking" your motor into running on a rota-phase; you can run your motor off your rota-phase converter and the motor (at load) can be pulling full load amps but if the phases are not in true 3 phase balance, some of the magnetic flux is being wasted and is being converted into heat without performing work (or not performing work efficiently). Please don't get me wrong. I am a proponent of using a rota-phase. I power my own shop with one. But when the equipment in my shop runs the gambit from 1/2 HP to 1-1/2 HP (and soon I'll add 3HP into the mix) and only one piece of equipment is running at any given time, there isn't a constant or consistent load. And you cannot tune the rota-phase to give good balance under all conditions. When you buy a rota-phase, the manufacturer will ascertain what is the largest motor you are starting and what is the total number of motors you plan to have running at any one time (i.e. total HP) and will sell you a unit that is the "best fit" for the circumstances. It doesn't mean that it will provide good balance under all circumstances. Now as to the name calling and belittlement. I think it is beneath this forum to use such tactics. Having friends and wanting to defend one's friends is a admirable trait. But I haven't seen you put up anything other than "my friend says..." I thought this forum was for the free exchange of information and ideas; the sharing of experiences and observations; and the occasional item for sale. I did not think it was the forum for a bully to vent his derisive opinions. Webb (11216)
I think we are both splitting hairs here. But this is where I disagree or misunderstood you. The Jpg you posted states that the motor should not be run at higher then 80% name plate rated load. Ok Fine but it also say you can run it up to full power and it will work. This is what I was saying. You can run it at full power. The converter will supply full power. your manual say's not to run them at full power but it doesn't say you can or the converter will not supply the power to do so. This is where we both got off track. I agree that all motors will lose "some" power to heat and magnetic loss. This is a known fact as you stated but I was not trying to be that exact. To truly find out if your motor is producing full horse power it would need to be connected to a dyno and a base line taken and I will bet you a years pay that it will not produce the exact HP rating on the case or will it pull the exact amps at that HP output. But I digress, we are here to learn from one another. I feel we were both right we just didn't explain ourselves correctly. Any way I was getting pissed as you could tell and vented when I should have cooled off before sitting down to type. I apologize. So we are in agreement on the fact that you can get the full power from a converter it's just not the best idea to use full power all the time. Although the guy that builds them and take it with a grain of salt says full power with 100% duty cycle. But you have a point he does sell them. Kerry (11232)
Kerry, I got a little p.o.'d too. I don't mind being called a 'moron' but calling me a liar, "Dem Fight'n Words!" Oh well, water under the bridge. But I would like to clear one thing up. The reference to running motors at full load was "method two" and that wasn't presented on the pages I posted (that was method three). The information is copyrighted and I worry about violating that copyright. Otherwise I would post the whole book. But to explain method two, there is an autotransformer (a multi-tap transformer) connected between one of the single phase legs and the generated leg (along with start cap.s and run cap.s as per a rota-phase) and is tuned to a specific motor (load). With this method, you can get full HP at full load with minimal heating BUT anything less that full load, the system looses efficiency drastically. This would be good for something like an air compressor where the load is pretty much consistent but lathes, mills, etc. are working at variable loads and this system is less desirable than "method three." Webb (11233)
Phase converter experiment/questions
Kerry Webb's discussion of phase converters made me curious. I am not an electrical engineer, just a facilities maintenance guy with a lot of electrical experience and a nice home shop. I am a slow typist, so I made my findings and my questions into a document on excel which is attached. Sorry if this is a little off subject. Bill (11406)
Read it an I agree that you have to have power to make it in a rotary phase converter. The guy I know said there's a radio station here that uses his 20HP converter to power something in there broadcast station it been running for over eight years with no problems due to the converter or motor. Kerry (11408)
Bill Not all of use Microsoft applications and I, for one, cannot read Excel documents. I am sorry I missed out on your thoughts - I read all the posts so I can learn. Frank (11419)
I agree with Kerry that rotary converters allow 3 phase motors to produce "NEAR" full horsepower. I believe that Webb's description of a "RotoPhase" was really referring to a static convertor that can only produce 2/3 of the rated horsepower, but is actually about 60%. I think the term "RotoPhase" was the culprit that caused the misunderstanding. I read Webb's attachment and his posts and the word "EFFICIENCY" kept jumping out at me, so I did a home shop machinist experiment. I have three machines in my home shop wired for 3 phase. I have a static phase converter made by "Phase-A-Matic", heavy duty version, 1 hp minimum 3 hp maximum rating. I also have a rotary converter made by "Phasemaster" with a 3 hp maximum rating. These units are mobile so that I can use either converter on any machine depending on the work load and the noise level I wish to endure. I hooked each of these machines up tp the static converter and took a reading inside the breaker panel using a clamp on ampmeter. Then I switched to the rotary converter and took a second set of readings. The results look like this : Bridgeport Mill 2J Varispeed Head 1.5 hp 220/440v 3ph wired 220v 1730 rpm nameplate 4.4 amp per leg @ 220v 3 ph static conv 4.4 amp per leg @ 220v 1 ph rotarty conv 10.5 amp per leg @ 220v 1ph starting surge 20.0 amp per leg @ 220v 1ph ramp-up 4 seconds to full speed / no load / 4200 rpm same with either converter Oliver 24" Patternmaker's Lathe Model 20-C 3.0 hp 220/440v 3ph wired 220v 1200 rpm nameplate 9.2 amp per leg @ 220v 3ph static conv 10.0 amp per leg @ 220v 1ph rotary conv 16.0 amp per leg @ 220v 1ph starting surge 48.0 amp per leg @ 220v 1ph ramp-up 15 seconds to full speed / no load / 2490 rpm same with either converter (4 step pulley - 3" flat belt thru 4 speed mech gearbox) Oliver 30" Wood Cutting Bandsaw Model 217-D 3.0 hp 220/440v 3ph wired 220v 850 rpm nameplate 9.4 amp per leg @220v 3 ph static conv 9.0 amp per leg @ 220v 1 ph rotary conv 15.0 amp per leg @ 220v 1ph starting surge 50.0 amp per leg @ 220v 1ph ramp-up 12 seconds to full speed / no load / 6676 sfm same with either converter (direct drive to lower wheel / wheels weigh 100 lbs. each) Observations: The rotary phase converter consumes 6 amps per leg (12 amps total @ 110v) at idle. This is the current used to generate the "third leg". I assume this will rise as a load is applied to the motor, but was unable to test this working alone. I don't know that 3 phase motors are any smoother or produce any more torque than single phase motors of THE SAME QUALITY. I do know that 3 phase motors are not harmed by the long ramp-up time and the heavy starting load of a machine like the bandsaw, since there is no start winding in a 3 phase motor. Single phase motors are designed to go from a dead stop to full rpm instantly. Heavy starting loads burn up start windings and can even break parts of the machine. I do know that 3 phase motors are "bulletproof" and tend to last forever compared to single phase motors. I do know that industrial sites save a fortune in wire conduit costs by running everything they can on 440v 3 ph. I'm sure the line loss is less, so the actual cost of electrical power is more efficient Conclusions: Static converters seem to be more energy efficient for the HOME SHOP, except for the loss of horsepower. Rotary converters use power to generate power. As Webb pointed out, unless the converter is matched or tuned to a specific load and fully utilized ( a 3 hp rotary being used to run a total of 9 hp of motors), the power consumption is not very efficient. Electricity costs here in California have soared will continue to climb. This cost is really important. We normally don't pass it on like a business. Questions: 1) Is the 1/3 loss of horsepower critical to the home shop machinist? Most industrial size machines seem to be overpowered for the requirements of the home shop. 2) Are you lowering the resale value of your home shop equipment by reverting back to 3 phase? Clint, don't you think that 9"SB lathe would sell quicker and for more money if was 110v or 220v single phase? 3) Is there any harm or long term damage done to the 3 phase motor being run on a static converter? (Jet states that the use of a static converter voids the factory warranty on their 3 phase machines) Kerry, maybe your freind that builds converters has some input on the long term effects. Questions: 4) Is the newer type of VFD producing true 3 phase electronically (all three legs all the time) or is it more like the existing static converters that run only two of the three legs after full rpm is reached? 5) Is there a version of this VFD that gives true 3 phase without the variable speed feature, for an application like the wood cutting bandsaw? By the way, my SB Heavy 10 is wired for 220v single phase and will probably stay that way in my shop. I find no fault with it and consider it to be one of the finest pieces of machinery I have ever owned. Also, nothing here is written in stone, so I invite comments and debate. I respect the ideas opinions and immense knowledge of this group love to learn. Bill (11424)
Frank Microsoft provides a free reader for all versions of Excel and it even works on old Multiplan documents if you rename them to .XLS. http://office.microsoft.com/downloads/2000/xlviewer.aspx  JWE (11426)
Bill, I read your post with interest. It is too bad that you didn't get amp reading from the three legs coming from your rotary phase converter to each machine. Contrary to popular belief, I do know the difference between a static phase converter and a rotary phase converter. I believe that my earlier statement about the output of motors being powered from a rotary phase converters being 1/2 to 2/3 of rated HP was probably too pessimistic. It would have been more accurate to have stated that motors may have 1/2 to 2/3 of starting torque. My apologies. I cannot stress enough that building a rotary phase converter involves some experimentation in order to get things in some kind of balance. I have notice that people who post their plans for rotary phase converters on the web, tend to oversimplify the variables involved in building one. Listing idler motor sizes and capacitor microfarad ratings should be looked upon as "recommendations" and not as "gospel." Looking at just the idler motor, one set of plans may suggest using a 5 HP motor. But they often don't stress enough that there are many possible internal differences between any two 5 HP motors. One may be Delta wound and one may be Wye wound. RPM's may be different, the rotors may be different, the pitch spacing inside the motor may be different, the amount of steel (iron) used in the stator may be different, etc. All these things affect performance and the same variables are at work in the motors on your lathe and mill. These differences will effect the size of the capacitors needed to balance the system. Now, as to efficiency; I take it from the point of a motor running off of a rotary phase can (or should if balanced) be able to run at 80% of its rated HP continuously. Getting full rated HP out of your motors for short periods of time is possible. Most machine tools don't run at full load all the time and therefore there would be in between times that the motor would "cool off" from the higher heat. One article posted on the web claims getting full HP out of your motors but only suggests it with motors having a service factor of 1.15 or higher ("Service Factor" or "SF" is the amount a motor can be overloaded for brief periods without overheating). Also, most of the machine tools we are likely to have are going to be older ones; built in the times when manufacturers often specified motors that were somewhat larger than necessary to do the job (a "fudge factor" if you like). And similarly, older motors were often build with that same philosophy (a "fudge factor"). The end result is that we can run our machine tools off of a rotary phase converter and perceive no loss in performance to our equipment. In conclusion, I am a proponent of building your own rotary phase converter. But I think the builder should keep their eyes open (and protected), check as many sources as one can, learn as much as one can and be prepared to experiment. Webb (11500)
Phase Converters
What kind of phase converters do you use on your lathe, Static or Rotary? (20151)
The static converter will reduce the capability of your existing motor. If your motor is oversized that ok. A rotary converter will give your existing motor almost full capability. If your considering a purchase, then look first at a Variable Frequency unit. (VFD) This will take in Single phase and convert it to three phase with variable frequency. It uses solid state technology and allows you, along with the normal change belts, almost infinite control of the lathe speed. It will also cost less than a "store bought" RPC. I just finished building an RPC for my mill. I got a brand new 1 1/2 HP 3 phase Baldor Motor on e-bay for $25 (all plus shipping). 10 dual section 15 and 4 uF capacitors for $16. I bought a large electrical box at the electrical store $35. A push button momentary switch for starting $5. And a 2 pole 1 Throw industrial wall switch $10. In addition I needed a 4 wire socket to plug the cord from the Mill into $18, a length of 4 conductor cable, $10, a plug for the cable, $18, a strain relief connector for where the cable goes into the RPC, $5, a small box to hold the second 4 conductor socket (different stile so the mill cant be plugged into it (either side of the 220 + neutral +ground) $2, Cover, $1.25 and the second socket $18, and finally about 10 feet of #10 3 wire + ground romex ($10). All of that came to about $140. I then needed some crimp connectors and wire to hook up the capacitors. By the time I got through I could have bought the VFD which would have given me more versatility, and taken up less room. It also took me a Saturday to construct the unit. If I were to do it again you know where I would go. Jim B. (20154)
I use a Baldor 220VAC, SINGLE Phase Instantaneous Reversible motor. Bought it 10 years ago for about 100 bucks. Works perfectly. Mounted into the spot where the original motor went with no modifications. I have a Heavy 10 dating from the early 60's. Eric (20155)
Depends on efficiency you want and price. Rotary is definitely best. Grumpy (20156)
Can you give me the exact # on the Baldor motor please. Grumpy (20157)
Amen, just went through that drill for the Hardinge mill. Chose the VFD after a fairly exhaustive analysis. You can get brand name new VFD's on Ebay for about $100. They may be last years model, but so what. FWIW, I also believe multi speed motors and static converters are a no no. Bill (20159)
I'll send it along when I get home tonight. Eric (20160)
It would seem like the general consensus is that VFD a better choice than phase converters. Have you considered this scenario? After much searching, I find a bargain, well cared for, little wear, but 3 phase SB lathe. No worry, I buy a VFD for approximately $100. I'm up and running. Now I find my next "dream machine", but wait it is three phase also. Another VFD purchase and so on. Or I could have bought or built a 5 or 7.5hp phase converter, wired it to a 3 phase breaker panel and had the freedom to add any machine I find up to the maximum horsepower of the converter. Simple to build, also available on Ebay. How is this a bad choice? Do it one, do it right and you have you own 3 phase power company. JD (20171)
That's the scenario that's played out in my garage. Years ago I had bought one of those horrid 3in1 combo units. The swing capability made it quite useful for the occasional repair work I've used it for over the years. As a drill press its fairly acceptable as well, as a mill it was next to useless. I had been eyeballing the Chinese mills and the X3 looked fairly useful. But I noticed that the 3ph 220v equipment was going ridiculously cheap in relation to the 110v equipment. So I bit the bullet and had the house 60amp service changed out to 200amp. I picked up a new 7.5hp RPC on ebay for 399 + 70 shipping. Instead of a 110v Chinese 9x20 and the X3 I have a nice Van Norman 3 axis power fed mill and am picking up a 16" SB lathe on Tuesday. The initial cost of the house wiring and rpc was made up for by the drop in cost of the old 3phase equipments low price. Mark (20184)
The main disadvantage of the bigger, rotary, phase converter compared to a VFD is that they are fixed speed. You may also find that the big boys need adjustment for each size of motor used. My pal Mike has a decent Transwave unit which suffers in this way so he has to adjust things depending on which machine he is using. Simple switches but still a pain, if its out of adjustment the motors still run but they don't sound happy. If you are considering going this route it might be worth looking into the more sophisticated VFD's which, I'm told, can automatically adjust their internal settings to match the motor. Fit each machine with a speed setting potentiometer and switch the control wires as well as the power wires on your breaker panel and you have the advantages of both systems. If I were to do this I'd put the no volt release relays / contactors in the panel as well and just take the control wires to the machine. Modern contactors take piggyback contact sets so there is no problem in getting enough switching ways. Probably need to use the "capacitor trick" on coolant pumps tho' as they really need to run at constant speed. Spend a touch more on plugged cables and its all a lot easier to handle. Standard 3 phase connectors for the power of course. I'd use crimp type QM multi-pole connectors for the control wires as they are about the nicest of the umpteen pin connectors to use, 7 ways should do the job. As ever its getting the cost/work/frustration index right. These days a lot of fairly sophisticated kit is around at not too hairy prices and I'm of the opinion that its not worth trying for a middle way, either do it really cheap or do it right and conveniently. The hassle factor of trying to save just a little just is not worth it. For example I will never hard wire a motor again. Short trailing lead to a plug, same for the control gear, so I can check it out on the bench and know it will go right when its in the machine. Clive (20186)
Clive, I guess I have to stick with my 3hp converter. Before I went that route I checked out the cheap VFD's on Ebay. I found no $100 dollar units as another member stated, there were some in the $100 plus range, but only 1hp. I have a 2hp on my lathe and the larger VFD's are either too expensive, ran on 440v and up, or were not single to three phase. The amount of control wiring you are suggesting to use a single VFD with multiple machines would seem to be well above the level of effort some of the member of this site would be willing to put in. One even balked at the day he spent building and wiring his rotary phase converter. With a single VFD wouldn't you have to change VFD control parameters as you moved from machine to machine? Maybe I am different, I'm not running a production shop, I get my enjoyment from figuring out and making things, almost anything, not just metal and machining. JD (20187)
I'm with Mark. When I got my 1st pc of 3ph equipment I bought a VFD for about $150. When I got my 2nd pc of equipment I built a 5hp rotary converter in an afternoon for aprox. $150. I can now run just about anything I ever plan on having in my shop. Another thing about the VFD. When you start slowing down fan cooled motors with the VFD you are now not getting the proper cooling and your killing your motor. My Bridgeport also makes some very odd sounds when running on the VFD. Jeff
(20200)
Rotary Phase Converters
When using a rotary phase converter to drive you lathe motor does this increase the amps used? (20484)
Andrew, Absolutely. Nothing is free! Do use an idler any bigger than needed. RichD (20489)
I have an SB13 with a 1hp motor. Use a rotary converter running a 3hp idler. It draws 7 amps per leg with just idler running. With lathe also running it uses 11 amps per leg. 3hp idler allows me to run other equipment (up to 12 hp total with nothing larger than 3hp) at the same time. Tried using static converter first, worked but not satisfied. This setup works perfect. Allows me to use equipment that others pass up at auctions etc because they are 3 phase. Craig (20505)
3hp idler. This looks worse than it is- the idler motor will show a high current draw when no load is placed on it, but the current its drawing is out of phase with the line voltage to a large degree, so the amount of wattage actually consumed when idling is not that high, especially if the idler motor is reasonably efficient. Even when the loaded motor is drawing heavy current, the idler motor doesn't double your actually energy consumption, I would estimate it adds 10 to 20% additional power load, again depending on the efficiency of the idler motor. Paul T. (20509)
New Motor? Rotary 3 phase converter
I had assumed that the rotary ran the motor on 3 phase while the electronic ran on 2/3. but, that you needed a 50% larger idler motor to deliver the rated hp because the idler was running on 2/3 also. ergo, to run a 2hp drive a 2hp idler would only deliver 1.333 hp and a 3 hp idler would be needed to deliver 2 hp. As far as VFD's go, there are constant torque drives and HVAC drives. The HVAC are designed to save energy and for use on centrifugal loads. These will deliver lower hp at lower speeds as the load does not require high torque at low speeds. The DC motor on my 9" and power is linear to speed. at low speed it is easy to stop. The AC drives are supposed to increase current to maintain speed so that if you have a 2hp motor at 1/10th RPM and put on a 2 hp load, the VFD will increase voltage and current to deliver 2hp at that load. Remember, all it need do is supply enough voltage an current to maintain RPM. Dave (23016)
Rotary converters can start with either a pony motor, or start capacitors (how I did mine). It really is in effect a rotary transformer, inducing a voltage in the third leg from the spinning armature, that can be tuned in for the proper voltage with run capacitors across the third leg. My converter under load is about 242 volts across any two legs via run capacitors. I used a recommended run capacitor starting point of X - MFD's per horse power, it was way to high for my set up. When I started it up I had 345 volts on the third leg under load, from only 245 from the wall outlet. I was able to zero it in by taking a lot of capacitance back out of the circuit. It does run at full power with 242 volts to all three legs. With a clamp on ammeter you can also match the current on the three legs too. I'm very happy with my set up, which I felt would be cheaper for me because I'm powering 5 different 3 phase motors all from the one converter. One but maybe two motors at one time. Jim (23065)
James Sounds good and justifiable for multiple existing motors if you don't want variable speed. James Waugh (23074)
Rewire for 1hp 110v. Phase converter
Check the motor rating amperage. This unit has good listings and the added variable speed is fantastic. Most phase converters are poor substitutes for real 3 phase. most electronic ones do perform poorly and rotary ones do better. The VFD notes on here that it offers 200% starting amps (not 500% that the motor wants) is still pretty good. I have not seen a review of users, but installed in a space with good ventilation, you should get good use of such a device. Note that they caution about motor cooling and slow speeds. Dave (23715)
I believe a better unit is: Automation Directwww.automationdirect.comGS1-21P0240 V SP AC Input1 HP 3 Phase Output.$159.This delivers 4.2 amps of output current, I fully digital, has current limiting on both the input and output, has a display, is keypad programmable and an internal fan. I got one for Christmas and its driving a 3/4 HP motor just fine. It does need an external on/off switch and it works nicer with an external (center off) forward reverse switch although the internal speed control pot can be programmed to go from full speed forward to full speed reverse. Jim B (23719)
I think I will create some web space and upload some pictures of my lathe and the drive train. There is a huge fuse box and transformer on the back of the lathe cabinet. The transformer I figure is to convert the 3ph220v to 1ph110v because there is metal conduit going from the transformer to the 110v outlet on the cabinet that powers the lamp. I just wonder if I should build a phase converter and run it that way. But then I would have to run a 220 line into my garage. That is more of an expense. I really would like to keep this project under $150. But then again I am having to run 8 more 110v outlets into my garage so what am I complaining about. Ben (23726)
Phase converter
I just picked up a 13 inch SB. It has a 1 1/2 horse 3 phase motor. What is the best way to convert to single phase? (25987)
You will get a lot of answers. 1) Build/buy a: a) Static Phase converter b) Rotary Phase converter 2) Buy a VFD (Variable Frequency Drive) 3) Replace the motor with a single phase motor Either the static phase converter or replacing the motor is perhaps the lowest cost approach. The static phase converter will however reduce the motor HP to about 3/4 HP. Before replacing the motor check to see of the reversing switch will work on a single phase motor. With a single phase motor you will not have "instant reverse" the motor must coast to a stop before reversing. The Rotary phase converter give full HP and instant reversing, if this is a consideration. This is not recommenced with a threaded spindle. Are you at all capable of doing electrical work? I built my RPC for about $135. The VFD approach provides true three phase AC at almost any frequency from a few HZ to several hundred Hz, This allows you to vary speed between the belt steps. You can go down to about 30 Hz which haves speed or up to 90 Hz which increases speed by 50%. These limits are for an older motor not designed for a VFD. As the speed decreases the torque is kept constant but the HP falls as the frequency. As the frequency increases the voltage is limited and the HP also decreases. I have a 1 HP VFD on a Burke #4 mill. It cost $140 plus a box to put in and some switches. It does allow instant or more correctly programmable soft starts and stops and reverses. There a lot of ways to go. I would estimate that replacing the motor could cost between $80 and $150 plus shipping. Try http://www.surpluscenter.com/ Jim B. (25990)
I have a 13" with 1 hp. 3 phase motor. I used a rotary phase converter. It works fine now. It is expensive, noisy and unnecessarily complicated. If I had a fresh start, I would change the motor to a 2 hp. Single phase reversing motor. Nick (25996)
I went with a Teco Westinghouse VFD and have been very happy with it, Almost does away with belt changing on my 13" SouthBend Dee (25998)
I forgot the benefit. When I want to loosen a chuck from the spindle, I put the lathe on its lowest belt driven speed, run it forward for a few seconds, then move the switch from "forward" through "off" into "reverse" quickly then back to "off". The chuck comes loose every time. Never tripped the OL relay yet. Nick (25999)
Personally I like VFDs, most of the time I'm not taking heavy cuts so the ability to change speed with the turn of a knob is very appealing. My VFD is on my mill where it is easy to engage back gear for those times when you do need the power. If you're interested I have a 1 to 3 HP heavy duty Phase A Matic that I got as part of my mill package and has only been used a few times, Enco # 297-3715. Drop me a email if its of any interest. Bernard R (26000)
Replace the motor. (26001)
Mort When I was looking for used mill I asked a lot of questions about motors and phases. I had real options, my house has three-phase though it uses all three phases individually, different parts of the house are on different phases -- so I'm careful when taking 230 Volt power from one place to another in case I accidentally connect two phases and discover an extra 140V in the equipment! Firstly, I asked about that the cost of installing good 415V distribution (it has to be GOOD, 415V accidents are usually very serious) was about the same as the cost of converters and replacement motors. But I can't take the 415V with me if I ever move house again. If you install 3-phase, will your electricity supplier make you pay an arm and a leg for the 415V connection? Friends who tried a 3-phase Bridgeport with different static converters never managed to get the head motor and feed motor working at the same time. Static converters are "tuned" to the motor(s), so if you have more than one motor to run they should be of similar size and characteristics for reliable simultaneous operation. Would you want to run more than one motor from a converter. The more expensive rotary converters don't have the one problem, but they are bigger and noisier. The cost difference may not be an issue if you have several motors you want to run. Three-phase motors running on one (converted) phase may not be reliable if you try to get the lower speed ranges out of them -- because their internal cooling fan (if they have one) may be running at the same reduced speed. I wouldn't want that. If you want a solution for nice versatile operation and reliability in a package, the Newton Tesla controls system + Misubishi 3-phase motor would be very hard to beat. Your supply voltage may be an issue for this system. Some useful information at: Newton Tesla: http://www.newton-tesla.com/index.htm Static and rotary converters http://www.phaseconverters.co.uk/boost/default.asp Have you tried e-bay for a replacement motor, or do have an integrated motor that's hard to change? My drill now has a beautiful-running used UK motor for half the price of a new far eastern motor, or 1/4 the price of new UK motor. And my mill? I looked a long, long, time for a Tom Senior M1 horizontal http://www.lathes.co.uk/senior/index.html with a vertical head, 12 spindle speeds, 36 feed speeds, and a suds pump all driven from one easily exchanged standard external motor. I was lucky and eventually found a single phase machine that fitted my wallet. It's been painted with a yard broom, and has has more dried out oil that a dead oil well, but there's a smooth running machine beneath the crud and paint. Alan (26002)
Dee, I was just looking at one of those. Where did you get yours? Was it hard to set up? I take it from your post that it covers a wide RPM range for you. Is this because you got a new motor? I heard that the effect is limited with old motors. Bernie (26003)
My home built Rotary Phase Converter, which uses a 1 1/2 Hp Baldor motor, is much quieter than the gear motor on the Burke #4 it powers. Jim B. (26004)
One negative about changing to a 1 phase motor is the additional wiring for reverse, unless you flat out decide that you're never going to use it. You might want to check if your starter switch supports that if you do think about going that route. Bernard R (26005)
Bernie, I bought mine from Dealers Industrial Equip Brooklyn Navy Yard, do a Google search it will come right up. I am running the original motor in the Lathe a Model CL145C Lets say all the instructions were in the book, that came with it , I did stumble around a bit , but finally figured it out. I put another one on my mill and the second one hooks up much easier!! I run mine up to 90 Hz so I am increasing the speed of the motor a bit and by using a speed control along with a fwd rev switch I can speed up or slow down the lathe, and minimize belt changes. Send me your email addy and I can send you some pic's of my installation if you want ? Dee (26008)
The noise is annoying when the lathe is stopped, like for a tool change for instance. You tend to get used to stopping both lathe and converter, followed by sometimes starting lathe without starting converter, instantly realizing why nothing is happening. The lathe makes more noise than the converter. The main reason that I went the converter rout is that I also have an old Bridgeport M head milling machine with a very strange looking 3 phase motor that does not look easy to replace with a single phase motor. BTW, on Wednesday I am going to Maryland for about a month to play with guns and a 1960 Austin Healey 3000 that my brother and I keep up there. When I come back, I would like to bring the Bridgeport back with me. As near as I can figure the 04 Ford F150 FX4, with big engine, big wheels, 3.73 gears and every heavy duty option offered, has an onboard cargo capacity of 1650 lbs. This truck moved my 13" with 6' bed SB no problem. Does anyone have any knowledge of what an M head Bridgeport with a 30 something" table and no power anything weighs? The guy that I bought my lathe from in 2000 practically threw the milling machine in for next to nothing, since as he put it "M head mills are worth next to nothing." At the time I was driving a U-Haul with 11,000 lbs. capacity, so, naturally I took the milling machine too. Nick (26009)
For motors up to about 1 HP the "add a couple of capacitors" type static converter works reasonably well and is not too expensive even if you buy new caps. I usually build them into boxes with NVR contactor and automatic start capacitor connection time out. Worth it if the machine has poor or "shudder bodged" electrics, marginally viable even if the basics are good. Beyond 1 HP static start needing proper tuning and maybe transformers. I have made the "add 2 caps" method work up to 3 HP but its never guaranteed. OK if you have a box of freebie caps to play with and time to spare but I'd not spend more than beer money buying stuff for a bigger motor. Reasonable rotary converters are not that difficult to build if you have access to a suitable source motor. However you need to watch the current draw, can get a bit hefty on start up. If you are buying stuff special costs need watching. Its easy to get embarrassingly close to E-bay prices for VFD's to produce something very home-made. People who have built converters tend, like moi, to have quantities of relevant stuff lying around and forget how much extra the little bits can cost someone who has to buy it all. Changing the motor or a VFD at E-bay prices are both pretty much one stop shop bolt-ons. Motor will be cheaper but you need to get a good one (not cheapy Chinese rated at input power draw rather than inefficiently produced shaft HP). Plenty of room for anything reasonably modern in the SB pedestal but its tricky lifting twisting doing the change. How good is your back! Personally I'd go for a VFD unless there are compelling financial reasons not to simply because its so much easier. Speed control is almost a bonus. Another advantage of the VFD is that the switching is built into the unit so you don't need an NVR contactor. If you do go for a motor swap don't forget that the standard three phase reverser drum switch from Cutler-Hammond etc can be re-wired to handle a single phase motor. Given the choice I'd re-wire a 3 phase drum in preference to using a single phase one! (26010)
Are you talking about solid-state or rotary phase converters? I have a solid-state unit on my 9 Model A that does pretty well. Everything except the belt and some wiring is original, including the nice GE motor. Mike (26015)
I replaced my 3hp 3phase with a single phase. It was quite an ordeal because mine uses starters and heater block. To reverse a single phase you have to change a lot more wires. I was surprised however that mine will reverse while still rolling and fairly fast too. I don't believe it's an instant reverse motor though. (26018)
http://www.surpluscenter.com/ E-mail Address(es): phaseam@p... Try this phase-a-matic address. they can clue you in on the specifics you wonder about. Henry (26019)
I made a 5 HP Rotary Phase Converter (Baldor Motor too) for about $150, it does make noise but it doesn't seem to be to excessive. Jim (26020)
Nick, Not sure about a "M" head but my 30" table "J" head weighs about 2500 lbs. George (26027)
http://www.frugalmachinist.com/bpwts.html  If you replace the 200 lb J head with a 100 lb M head (mine weighs about that), the total is somewhere around 2000 lb as a rough estimate. This doesn't account for different models, but is probably close. Irby (26037)
Best way is don't do it leave the 3 phase alone. You would be getting rid of a very well built motor that could last for years. Get a VFD on EBAY and go on with you life. With a bit of work, it took a while I converted a drill mill to Single phase. But that was nothing compared to converting a 13 inch SB lathe with motor frame sizes that are long gone. I replaced a static converter on my 13 inch SB lathe with a VFD - Single Phase to 3 Phase output "What a Difference". It runs like a modern machine. I have complete control over the speed and direction of rotation at a touch of the button. And it will keep you from killing your self. Let's say you get some crazy ideal of instant reversing a 2 1/4 threaded nose mounted 35 pound chuck. Not a good ideal for many reasons. Touch one button the motor will come to a slow stop, reverse and come back up to speed again. Once you see a VFD in operation you will understand the difference. (26067)
I endorse what Steve says. Is the motor you have already 240 or 208V, 3ph.? The VFD has so may advantages like a programmable soft start to minimize the effect on lights and other equipment. But choose a good Mfr. with adequate current rating, allow for 208 V motor current if you are using 240 V single phase supply without a transformer. Jim (26079)
I am interested in these VFD s. On ships we used a similar type of device to drive a small fractional horsepower positive displacement pump motor to vary the feed rate of heavy fuel to the centrifugal heavy oil purifiers. Feed rate was one of several factors that were critical in making one of these, troublesome, laboratory like, devices work properly in an industrial setting. Obviously, feed rates also had to equal or exceed Main Engine fuel consumption. These things were programmable very much like a programmable logic controller. They came with a comprehensive book that wound up with greasy finger prints on the pages that discussed varying the output frequency. Changing the output was not easy for those new to the device, as it required correct sequence small button pushing. There were several steps required before using the up or down arrow buttons and a couple of steps required to lock in the new setting. On a lathe I could see it as useful to be able to reduce speed as diameter of cut increases in a 6 or 8 diameter facing operation, for instance, when making a chuck back plate. The ones we had, on the ships, were 3 phase 450 volts in and 3 phase 450 volts out, only frequency varying as we used them. Please try to overlook my ignorance of the VFD s discussed here, as I have not seen one. Can I keep my old properly fitting 3 phase motor? Can I do away with the rotary phase converter? As I have only a one horsepower motor, do I loose any power like you do when using a static phase converter? How much can you vary the speed of the motor without damaging it? About how much does one of these VFD,s cost, sized for a one horsepower motor? Who makes or sells them? Nick (26086)
I have a 1 HP unit driving a 3/4 HP motor on one of my Burke #4's It is from Motion Dynamics. Cost $139. You will still need a box to put it in and two switches, on/off and forward reverse. The on/off must be capable of handling the 1 HP on single phase input. You could use the programming buttons for forward/reverse but its tedious. The unit I have requires 240V single phase AC it delivers 220 V 3 Phase at any frequency from 0 Hz to over 400 Hz. This is very true 3 Phase. The unit first makes DC and then the DC is "chopped" at over 12 KHz to produce three sin waves 120 degrees apart. The unit is current limited at 4.2 amps per phase and of course the voltage is limited to 240 There is a unit which operates on 115 input and provides 240 3 phase out but, from Moton Dynamics, they do not go to 1 HP (I think there is a more expensive series which may). Thus as the frequency is lowered the motor torque is held constant but the output HP decreases with frequency. With an older motor I would not suggest going below 30 Hz or 1/2 speed, except under light load. As the frequency is increased, and because the output voltage is limited the HP also decreases. I would not suggest that you operate an older motor beyond 90 Hz or approximately 1.5 times the normal motor speed. The units are programmable in more ways than you will ever use but the soft start/stop/reverse is very nice. Mine has a LED readout which will provide output current/voltage/frequency and motor RPM based on output frequency. Jim B. (26088)
Nick, when I converted my Unitech mini-mill to a variable speed I used 3-phase/VFD. Because it is a German mill that uses a metric frame motors, a desire to keep the mill variable speed ruled out a DC variable speed conversion. 98% of all DC motors in a metric frame are 180V, that require 230V into the Controller. I bought a .7 HP Lefert 3-phase motor and a Leeson 1 HP speedmaster VFD that takes 115V input. I was able to use the same power buttons, and the conversion was seamless. The lowest speed, before conversion, was 440 RPMs. Now the lowest speed is 0. The OEM motor was 1/3 HP (250W). I bought a .7 HP (500W) motor, because if you run it 30 Hz, you get a 250 W output, and at 20Hz, 180W power output. Below 60Hz, HP decreases at a constant rate, and after 60 hz, torque decreases at a rapid rate, with next to no torque at 120 Hz. In order for me to get good power at lower RPMS, I had to double the motor size. Since conversion, however, The mill is 50% quieter than the split phase motor it replaced, the need to move the belt on the step pulley have decreased by at least 60%, and it has serious power when ever I need to rough a part out with a roughing endmill. It cost $400 total to convert it, due to VFD cost and Special order motor, but has been well worth the conversion. Since your SB Already has a 3-phase motor, all you need is the VFD. Don't shut the lathe on or off by using the drum switch in the power cord from the VFD to the motor as that might shock and ruin your VFD. Read the manual, and use the control bar on the VFD to start, stop or reverse the lathe. The VFD knows best how to cut power to the motor, you just program it to work in your situation. Older motors got their HP ratings slightly differently (old 1/2 hp ~ new 3/4 HP) as today's motors are rated on amount of load to stall them, and the old motors on their overall run power. Go to your bearing supply/local motor dealer, look on ebay, or go to surplus venders. I bought my setup from the local motor dealer because 1) I could not find the motor on e-bay, 2) could not find a VFD with the desired input/output on Ebay and 3) If you buy a used VFD from e-bay or a surplus vender, and it doesn't work, it will be near impossible for you fix it or diagnose what broke on it. With the Surplus DC route, if you reasonably knowledgeable with electronics, the DC controller, if it doesn't work, it can be tested with a multimeter, and has a chance at being fixed, as all they are are SCRS/PWMS, caps, resistors, ICs, etc that can be individually tested. With a VFD, there is no such luck, as they are PLCs specifically designed to control motors. Also, if you screw up or the VFD breaks, getting one new includes a 1-year warrantee (something I've had to do with the first VFD setup, where a board shorted). Gabe (26094)
Modern VFDs are reasonably straight forward, mine is up to 3HP for a mill, but most have much the same features. Though they are capable of round 400 Hz or higher, you set the maximum frequency you are comfortable with. I set mine to 120Hz but my motor is dual speed and is switched for the slow speed, this allows me to go from 0 RPM to full rated motor RPMs at the turn of a potentiometer. Nearly all current VFDs allow remote speed setting by means of a potentiometer, most also have remote Start/Stop and Reverse by simple switches. I mount the remote switches and potentiometer in a small box attached to the mill and have a standard wall mounted box for the 220VAC switch to the VFD. Bernard R (26095)
Jim, Tried to look for Motion Control with Google and struck out. Where did you get yours? I wondered if they had a 2HP unit for my Bridgeport. From your description, I would bypass all the control box on the H10 and drive the motor directly from the VFD. What do you use to switch the 220 line to the VFD? George (26111)
Go Here http://web1.automationdirect.com/adc/Shopping/Catalog/AC_Drives_-z-_Motors/GS1_(120_-z-_230_VAC_V-z-Hz_Control  for 3 Hp units go here http://web1.automationdirect.com/adc/Shopping/Catalog/AC_Drives_-z-_Motors/GS2_(230_-z-_460_VAC_V-z-Hz_Control  Ordered Direct. I used a toggle switch. The first one went zap. I went to an electrical store and got a HD unit SPST. Has been working since. Yes for F-R I used a simple low current toggle with a center off position Radio Shack. There is a picture on the Burkemill site. I can send it to you tonight when I get home. Jim B (26116)
Phase converters - Instant reverse
There has been a lot of talk lately about being able to instant reverse 3 phase motors. I do see a need for reverse, in both lathes mills, but not in going from forward to reverse instantly. Why would anyone want to instant reverse a lathe, other than loosen a chuck? I don't see any reason to instant reverse a mill either, am I missing something? Jim Sterner John Peters wrote: I replaced my 3hp 3phase with a single phase. It was quite an ordeal because mine uses starters and heater block. To reverse a single phase you have to change a lot more wires. I was surprised however that mine will reverse while still rolling and fairly fast too. I don't believe it's an instant reverse motor though. Leon (26021)
That is one advantage of a VFD if you set your parameters to do so the lathe will slow to a stop and then start in reverse , handy for things like knurling. As far as instant reversing I suppose it could be set to do that, but not my machine! Dee (26022)
I do see a need for reverse, in both lathes mills, but not in going from forward to reverse instantly. loosen a chuck? missing something? One of the nice things about a VFD is that it has a programmed acceleration/deceleration parameter. This keeps you from throwing the motor in reverse under speed. By the way, the other nice thing about a VFD (as opposed to a rotary phase converter) is that many will display RPM. (26023)
Tapping operations with a cam lock chuck only or collets not screw on chuck. Actually unscrewing a chuck with the motor I think is ! Well lets just say you ant seen nothing till you seen a chuck run loose in the shop. Grumpy (26043)
I agree in principle, but have done plenty of tapping on Logan lathes with threaded spindles. I try to avoid having the spindle reverse too rapidly, letting it slow a bit before hitting reverse. If the machine is running on single phase power, that is probably not an issue for most people. Scott Logan (26044)
 
     
 

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