I recently was given a shaper from a shop that didn’t use it. It is an old Onsrund, which is no longer made. The problem I have is that the shaper uses a 3 phase, 7 horse motor. I can’t get 3 phase power run into my shop (cost prohibitive), so I was hoping someone could suggest an alternative. Single phase would cause me to sacrifice variable speed. I have a single to 3 phase converter on my lathe that works well, but it is only rated up to 3 horse power. Any suggestions or comments would be helpful.
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Replies
Either find a used single phase motor or a phase converter that can handle the 7 hp .
good luck dusty
For your purposes, will you actually be USING the 7 HP supplied by the motor? If your work requires less power then you might be able to use your existing converter. In any case, be certain to properly fuse your converter if you try to use it for the Onsrud.
You didn't mention what type of converter was on your lathe. I would suugest a larger rotary which will work on both machines or a Variable Fequency Drive which would be for one machine as it's a pain to reprogram for each machine so it would be dedicated. It gives infinitely variable speed. Best prices are at http://www.factorymation.com
As Rick mentioned, variable frequency drives (or VFDs, or AC drives, or inverters as they are sometimes called) can be a good way to operate a three phase device when only single phase is available, and you get variable speed control to boot.
You didn't mention the voltage of the shaper, but for this to work it will need to be 230vac three phase; if it's 480vac or something else, you'd also have to get a big transformer and the whole setup gets messy fast.
VFDs are normally used with three phase supply voltage, but many of them can be operated on single phase and they'll still generate a three phase output. However, you need to check with the particular manufacturer; some companies require the VFD to be derated when it's used in this fashion, others don't.
There are a million brands of them these days, both from the major companies like Allen-Bradley, Cutler-Hammer or ABB, and from many small companies that you've never heard of. The off brand ones are going to be cheaper; I can't make any specific recommendations but the one low priced company I am familiar with is Automation Direct at http://www.automationdirect.com.
Thanks for the input... The moter can be wired for 480 or 230. I took it to a shop and had it checked out. They cleaned it up and added a new schematic plate for me as the old one was worn off. I am not an electrician, so all this is rather new to me. I am extreamly happy with my 2 Hp 3-phase lathe. Very quiet and 0 - 3,600 RPM with a twist of a knob.
I think you might be confusing your lathe's VFD with all 3-phase motors. A 3-phase motor is not variable in speed without a variable frequency drive. Your lathe may have this built-in, but it is doubtful that your shaper would.a 7 hp VFD will cost you an arm and a leg. I haven't checked in a while, but I believe these will be close to $2000 for a VFD of that size. Your best bet for a 7 ph motor is to find a 7 hp idler motor and build a rotary converter. This can be done for a few hundred dollars.
Rick,
You are correct in that the 2 HP motor and the VFD are separate devices. Perhaps I didn't describe the setup very well. The 2 HP VFD was about $650 when I purchased it about 5 years ago and the motor was only $250. The pricing on VFDs for 7 HP motors are running around $2,000. I was hoping this discussion would generate some alternative ideas... Thanks for the input...<!----><!----><!---->
Variable speed control on a shaper is not all that important. For the most part, you put it in high speed and leave it there. The only cost effective alternative is to build a converter. You could buy one, but the cost is also going to be high. Hunt around for a cheap or free 7 hp motor and you can build a converter for less than $100 (not counting the motor). Actually, because your shaper does not start under a load, it would be a perfect situation for a static converter, and this you can build for less than $100 complete. There is an article on my website on how to build and balance a phase converter. Store-bought static converters aren't balanced to the tool.
http://waterfront-woods.home.att.net
Thomas ..I suggest you look at the attached web site for Phase converters. I have one of theirs and it is working great. Some people have issues with the amp ratings required from your single phase panel but I would suggest you speak with Gen Tec or any other supplier and form your own opinion
http://www.americanrotary.com/product.php?productid=10
http://www.factorymation.net/s.nl/sc.2/category.40/.f
Factorymation sells a 7.5 hp VFD for $399. Haven't bought from them yet but have talked to one of the owners.
That one, as well as most VFDs of more than 3 hp or so rating, requires three-phase input. Be seeing you...
Good point about the larger VFD's. I was just researching VFD's yesterday to upgrade my old 1-hp Oliver lathe from phase converter to variable speed. Most VFD's above 1-2 hp require a 3-phase input, so they are not applicable for phase-conversion on larger motors.I don't know anything about "2x4's" (Brian's) Gen Tec rotary converter, but after a previous discussion on this topic it does appear to be a very good converter, and far surpasses anything I have seen previously, or what you can build on your own. I'd like to get my hands on the Gen Tec to see how they achieve their stated efficiency; but if their numbers are correct, it is an incredible converter and well worth the cost. **********New Edit 9-6-06: I rescind this statement based on new observations from the American Rotary Website. See my posting below for an explanation.********Brian, I don't suppose you would be willing to snap a couple of pictures of the inside of your control panel would you? Your converter has really piqued my curiousity in the past 24-hours, and I am dying to figure out how they built it. I have a feeling it is more than just the efficiency of the specialized idler motor as they state in their website.
Edited 9/6/2006 3:33 am ET by RickChristopherson
Rick,
I installed a 7.5 HP RPC ( rotary phase converter ) from american rotary and am very happy with it. The big thing you must remember is not only the HP rating of the motor, but also the service it will be working under. Machines are rated as either Hard, Medium, or Easy. Your shaper is a medium to hard load. For a hard load, you must double the motor HP to determine the minimum size RPC to run your machine. In your case, I would go with a 15 HP RPC. You will then have the ability to run other 3 phase machines in the future. Check the american rotary website out and look at the circuit requirements. You will need an electrician to wire everything for you, since you have limited electrical background, adding to the cost.
Will, Pa
After having a pleasant conversation with the lead engineer of American Rotary, I am replacing the original posting I made on this topic with a new posting. I am doing this to avoid confusion with the questions I was posing in my original posting.As an Electrical Engineer, I am trained to question everything, and the more something appears to be too good to be true, the more it needs to be questioned. This questioning was the intent of my original posting, but admittedly, the introduction into my questioning sounded more accusatory than I had intended it to sound.My original confusion on this topic arose because I thought American Rotary was using a smaller idler motor than their ratings implied. I have since then confirmed that my suspicions were not correct, but more importantly, I was able to identify where and how my confusion arose. (AR is now aware of the how’s and why’s of my confusion.)I am satisfied that the American Rotary phase converters perform as they indicate in their web site, and moreover, I actually endorse them as being one of the better phase converters I have come across. (I don’t normally endorse one product over another.)It should be noted that the things from their web site that caused my original confusion are not the types of things that your average buyer would have noticed. More importantly, the confusion was related to understating the specifications of the converters, not overstating them. This is a significant distinction because it is to the benefit of the buyer, which is something I firmly uphold.
Edited 9/11/2006 5:06 pm ET by RickChristopherson
About American Rotary....I have been successfully running several machines with my converter from American Rotary for several years now without a hitch. They have tons of resources on their site – as well as 24 hour technical support - that you may want to check out for more information about how they do things. They also make mention many times to call for sizing assistance when using multiple motors. I found their method of sizing the converter to the load to be very straightforward. They have a great sizing page that describes their multiple motor load sizing procedures:http://www.americanrotary.com/pages.php?pageid=25I just can't say enough great things about this company. They have absolutely the best customer service and technical support that I have ever encountered - not to mention an amazing product. It is unfortunate that these forums are sometimes used to make hasty assumptions about a product or company.WaltEdited: The poster whose assumptions I was referring to in the last sentence has since seen the light and edited his post. Definitely a stand up guy.
Edited 9/11/2006 9:43 pm ET by time4tinkering
"It is unfortunate that these forums are sometimes used to make hasty assumptions about a product or company."
What hasty assumptions are you referring to? Are we not to question when someone appears to say they have a machine that appears to violate the laws of physics? Are we not supposed to ask for more information that would help us resolve the apparent discrepancy just because the company has great customer service? I have seen a lot of thoughtful posts on this subject on this forum by people who obviously took a considerable amount of their time to ask questions and crunch numbers. Are we to just make the hasty assumption that because someone says so you can get more power out of a process than you put in? I am glad yor converter works well for you and that you are pleased with the customer service, but don't make the hasty assumption that we are making hasty assumptions.
Since the house is on fire let us warm ourselves. ~Italian Proverb
I guess it is because I took the time to call the company and let them explain it to me instead of making accusations in attempt to make myself look smart. I just think that discouraging people about a product when they may not have all of the information is a very unethical approach to use in a forum or elsewhere. Questioning is fine. Calling a company's methods "blatently deceptive" based on some limited knowledge of their product - isn't.
Did he not in the same sentence say that he assumed it was a mistake on the web site?
Do you have numbers and formulas based on physical laws of nature to refute his findings?
Do you understand the methodology he used to arrive at his conclusions?
If you do have evidence based on something other than a conversation or webvertising that is replicable using the known laws of physics please share it with the rest of us, as you can tell from the thread we are quite interested.
Since the house is on fire let us warm ourselves. ~Italian Proverb
"Do you understand the methodology he used to arrive at his conclusions?"I understand that his assumptions are wrong so his conclusions are useless. He is assuming that all of the current to run the additional motors is running through the phase converter, which entirely depends on how you hook up the phase converter and more importantly, how you hook up the additional motors. The different wiring diagrams for the different scenarios are very clearly shown in the instruction manual I received with my converter from American Rotary. So far as I have read, the folks giving their 2 cents in this forum that HAVE a converter from American Rotary seem to know more about how they work than the folks in this forum who consider themselves experts on them...
There are two threads with discussions of these converters. In the other thread (I think it's power for the shop) one of the posters I believe did say all of the current was being supplied by a single 60 amp circuit.
For those interested here is a link to American Rotarys schematic for powering motors at up to 3 times the rating of the converter.http://www.americanrotary.com/images/rotarywiringdiagrams.pdf
I am interested to hear the results of Ricks conversation with A/R.
Tinkerer for someone who professes to know more than the experts, the expertise you have shared with us is as useful as teats on a fish.
Since the house is on fire let us warm ourselves. ~Italian Proverb
It is me that is running my phase converter on a 60 amp single phase circuit and it is a 20 hp Rotary phase converter. I share the others concern about making negative comments about any commercial enterprise when you do not have all the facts. It has been suggested that my system will not work as I described due to laws of physics. All that tells me is that somebody does not have all the info they need or their knowledge of rotary phase converters is not as thorough as they believe. The 60 amp breaker was suggested as a minimum by my electrician and I confirmed that with American Rotary. I also realize that if I was to place a further load on the current system I would need a breaker with a higher amp rating. The current syatem is working admirably and to me that indicates that American Rotary is a good company to deal with and I will always be a loyal customer.
Brian
And as I said we are trying to get more info. I took umbrage at his crack about hasty assumptions . I think you will agree the discussion has been anything but hasty. Effort has even been made to clarify things with the company. When someone makes a claim that appears to good to be true there is a discrepancy in the information somewhere, hence the questions in an effort to understand. You have endeavored to provide information about your setup as best you can with amperages, voltages and motor ratings,you freely admitted you didn't understand how it worked, so far so good. The other poster offered nothing but a claim that his system works and a rant that we were hastily trashing a company.
Since the house is on fire let us warm ourselves. ~Italian Proverb
Hello fellow woodworkers, I am new to this forum and joined to learn a little more about my new early retirement hobby of woodworking (I would like to make wood strip kayaks), but my career as an electrician keeps haunting me so I find myself in a discussion about phase converters. So much for retirement, eh! Just a little background... In my last years as an electrician I found myself installing the power for CNC equipment more and more – and lots of phase converters. It is amazing where you will find machine shops and woodshops. Over the years, I have installed probably every known brand of phase converter, as well as made a few myself. So here is my perspective as a newbee.There are many different ways to hook up a phase converter and there is no standard, just what the manufacturer recommends as standard. Looking at American Rotary's site, they have two wiring diagrams in their installation manual. I have hooked up phase converters in both these ways. (including many American Rotary brand converters and GenTecs before they were American Rotary) They both accomplish the same thing, but one definitely has the capability of extending the useful load range of the converter, and not only to 3 times the rated current of the converter. Actually there is no real limit. By the way, hooking them up in this fashion does not work for CNC equipment, only simple manual machines with motors. When I install a phase converter is this way, I will usually, depending on how much room is in the load center, run two pairs of wires from the same breaker. One pair powers the phase converter, and the other pair feeds the equipment. Then I run the manufactured line from the converter over to the machine to complete the 3 lines of the three-phase circuit. Care must be taken to turn the converter on before the other machines. I like to put a motor starter between the converter and the machines and operate the latch circuit of the starter using the manufactured line. This way, the power can not get to the machines unless the converter is on and the machines are not turned on with only two lines coming in. I digress.As more machines are used, the current manufactured by the phase converter (just one line) starts to migrate to the machines and away from the converter. This current is somewhat limited by the capacitance in the phase converter. The machines take the current they need to run on the two lines and the phase converter supplies some current on the third line. But as more machines are added, this total current that is shared between the converter and the machines doesn’t go up, so overall it becomes a smaller percentage and the lines become imbalanced. The "Rotary" or dynamic phase converter is quickly becoming a "Static" phase converter as the machine loads are increased.As for one of the members of this forum, I think he is confused and making the assumption that the loads are hooked up in a way that makes all the current feed through the phase converter. This is only one of many ways to hook up any rotary phase converter and maybe the assumption was made that tapping off the output side of the converter is the default or standard way, but believe me it is not. There is no limit as to how much hp or current can be run in this way, and the FLA of the phase converter never gets exceeded. In fact, the current on the manufactured line to the idler goes down as more load is added. So to defend American Rotary, their specs appear to be accurate and so are their claims to be able to run up to 3 times the current or hp of the converter. You just must follow the instructions which come with the phase converter, and any good electrician knows how to do this. Neither one violates the other one. In fact, they could claim you could run as much hp as your want, but they don't and I think that is wise because it is not practical.So to be thorough, I was curious as to how other companies that claim the same thing, and there are many, explain how this works. So I called 5 of the major ones that I have purchased many from including Phase-A-Matic, AmericanRotary, Ronk, Kay, Arco and GWM and I got 5 totally different answers. No one except the engineer I talked to at one of the companies (I will not name names in this forum...no way!), and the tech at another company got it right in my estimation. They both sort of said that the 3 times number is just a practical number to use and that sizing wire past that gets out of hand and that their is really no limit to the number of motors that can be run in theory. In my experience, this is absolutely correct. I hope this helps.Don Kohler
Don.. Thanks for taking the time to share your knowledge with us. An informative post.
Brian
Walt,
I did not say that American Rotary does not make good converters. As a matter of fact, I believe I even commented on the fact that their Idler motors appear to have an efficiency that is higher than typical. My previous comments were not related to the performance of the converters themselves, nor on the performance of their staff in helping customers.I am duly impressed with the converters, but what I am questioning is how the converters are marketed on their web site. I made these observations because I believe that some people have been confused about the capabilities of the converters. This is an open issue and I am waiting to hear back from them regarding the specifications they present on the web site.American Rotary is aware of my previous posting and I am in contact with them on a high level. Even though I was planning to do so anyway, I did tone down the wording of my previous posting, but I have left the technical information intact unless I learn otherwise. If American Rotary can refute my information, then I will make the necessary corrections to my postings.I have in fact modified my original posting. See it above.
Edited 9/11/2006 5:08 pm ET by RickChristopherson
Rick,I am glad to see you were able to do some more research on the American Rotary specifications. They truly are the cleanest and most thought out, well built phase converters I have installed in my 20+ year career as an electrician, not to mention affordable; these guys know what they are doing.Don Kohler
Brian,
You seem to have a good grasp on how rotary phase converters work.
I read over some of your earlier posts and just thought I would explain to the readers of this post about why your electric bill is so small with your American Rotary phase converter. When your idler motor is just running idle, no machines running, the 3-phase current is somewhere between 20 and 40% of the full load amp rating of the motor. So if you are running a 30hp converter, 30% of 160 amps (Full load single phase amps) is 48 amps. About 80% of that current is reactive current, in other words it is not doing any work or making any heat. This current had to come through your meter, but it now gets put back through the meter and slows it back down. So you are only paying for 20% of the current. 20% of 48 is 9.6 amps. 9.6 amps x 240volts is 2.3 kw. This is what you are paying for. Not much for a 30hp converter. Now when you add a load, you are doing real work and you pay for the current that your machine uses. But something similar happens when a machine runs at idle, and no work is being done, it uses reactive current and you don't pay for that. That is why it is often cheaper to let a machine run when it is being used on and off rather that starting and stopping it all the time. That take real power and you pay for that. The American Rotary spec on the 30 hp says the idle power is 2.55kw. so I am close with my 2.3kw. I am sure that is what they are publishing because their next spec is cost to run at $.10/kwhr. So they are giving you the power that really matters to you, the power you pay for. This is why rotary phase converters are so inexpensive to run. I tell most of my customers if they need to turn the converter on and off more than 5 times a day to just leave it on. Most people don't see any difference in their power bill. Over the long haul, it is cheaper and better to run three phase equipment because they use less power and they last longer. Not to mention the equipment that is built around three phase is usually built better.Edit: Thought I would add the numbers for your 7.5hp converter.
FLA single phase is approx 44amps, 30% of 44 ~ 13 amps. 20% of 13 amps ~ 2.6 amps which is approx 0.63kw at 240 volts which is close to the specs of 0.70kw for your 7.5hp unit. http://www.americanrotary.com/product.php?productid=9Hope this was useful.Don Kohler
Edited 9/13/2006 2:20 pm by cncelectrician
Don... I take from your last post that It is fine to leave the converter running with no load on it. I am not concerned about the cost of running as long as it is not causing problems within the phase converter.
TIA
Brian
Brian,You are correct. The output current has to be balanced on the phase
converter to avoid overcurrent on one or two of the windings. Most
converter companies balance the voltage high to gain a little more
starting potential. American Rotary converters come pre-balanced for CNC equipment, which typically means that the line to line voltage is within 5% of the single phase line. This is why it is okay to let it run. It also allows you to run machines much smaller than the phase converter without damaging them.Don
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