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Thread: Phase convertors?

  1. #46
    Quote Originally Posted by Erik Loza View Post
    Kurt, I'm going to float this out there: Feel free to accept or reject as you like. I've been witness to this exact conversation with hobbyist ww'ers MANY times and it invariably goes one of two ways.

    #1.) After running through all the mental gymnastics of what it would look like to actually acquire your ideal used machine (which often doesn't exist), and after running through all the mental gymnastics of getting a phase converter installed, the customer ends up back where they started and just buys a new 1-phase machine.

    #2.) After running through all the mental gymnastics above, the customer decides it was just too much and ends up sticking with whatever smaller machines they have and never actually buy anything after all.

    Not saying this is necessarily you, Kurt, just that I've seen the this scenario unfold many times in the past. Yes, there are some hobbyist owners here with three-phase machines and converters in their home shops and that's great but they would definitely be in the minority and more importantly, from a woodworking perspective, there is nothing you would be doing that a decent single-phase saw in the 4-5HP range couldn't accomplish. Your wallet and you should do what you want but from a buyer's standpoint, I think probably will find that by the time your search is over, it might even be cheaper to just get a 1-phase machine and be done with it so you can get on to actual woodworking. Again, just an opinion from a different perspective and good luck in your search.

    Erik
    Thats good advice. There's another trap too; if you buy a 3-Phase converter at 240v, you may end up needing 480v for some equipment. The idea of buying another voltage doubling phase convertor or adding transformers is just more "mental gymnastics". (Note: talking about a machine that has a 480v VFD in it etc, not a motor that can be rewired)

  2. #47
    You can find used transformers for pretty cheap and that solves the 480v issue. I found a 7.5 kVa 240 -> 480V barely used 3 phase transformer for $100 from a regional electrical supply after a few weeks of looking for a good deal somewhat locally.

    Also, it’s not like you wouldn’t know the machine was 480v only...that would be something you’d assess and figure on prior to buying the machine.

    Don’t get me wrong, there are some mental gymnastics with this stuff, and it does require either some effort and/or $ to put in place, but it’s relatively simple and the answers are out there and available if you look. If I can do it, anyone can.
    Still waters run deep.

  3. #48
    3 phase 240v is very common on used industrial grade woodworking machinery, way more common than single phase. I have been fortunate to acquire machines from the golden age of American machine tools at crazy prices because of the 3 phase motors.

    I set up my first RPC in 1977 based on a Fine Woodworking issue that showed up just in time to help me get my 32" Crescent band saw up and running. I bought an idler motor for about $20 and a couple capacitors and went on to add many more machines.

  4. #49
    Quote Originally Posted by Phillip Mitchell View Post
    You can find used transformers for pretty cheap and that solves the 480v issue. I found a 7.5 kVa 240 -> 480V barely used 3 phase transformer for $100 from a regional electrical supply after a few weeks of looking for a good deal somewhat locally.

    Also, it’s not like you wouldn’t know the machine was 480v only...that would be something you’d assess and figure on prior to buying the machine.

    Don’t get me wrong, there are some mental gymnastics with this stuff, and it does require either some effort and/or $ to put in place, but it’s relatively simple and the answers are out there and available if you look. If I can do it, anyone can.
    You had better luck than I. I assed it and I couldn't find a new transformer at the rating I needed; after a week of talking to Wolf Automation, I gave up. I think it would have been price prohibitive anyway. I think that was Erik’s point. I went with a different SP model instead because it wasn't worth the effort or expense.

  5. #50
    I guess it depends on your tolerance for searching. I’m always looking at/for any number of things or subjects so it’s only natural for me to pivot the focus to something new should it become a more pressing need.

    I also don’t have a lot of extra cash so I do not typically buy things new unless there is no other option for months on end and even then sometimes go without or find another way out of necessity. If I was pricing new transformers (I did briefly) then that would have been a non-starter for me. The transformer I found for $100 used (and professionally tested) would have been well over $1k to buy new on the spot, so you can see the value in searching for a few weeks for good condition used.
    Still waters run deep.

  6. #51
    Here is a question I wondered when I sold that static phase converter. Essentially all it is, is a capacitor bank that times out to be able to start the motor. I have heard some people start one machine and let it idle while running some different machine on the same circuit.

    If you have a static phase converter, and then buy a used 3 phase motor to run as idler, do you then have a RPC? Any rewiring needed at all?

    If so, then there is no down side to trying it out. If the SPC isnt enough for some reason then just add a used idler motor.

    (on voltages: once I open up my shopping to 3 phase 208 v machines, it increases options a lot. I havent noticed as big a jump in available equipment between 200-400V ranges (meaning, I can almost always find what I am looking for in 200V ranges - so have never felt a need to bump to 400. And 208v 3 phase motors are pretty plentiful if I wanted to swap down))
    Last edited by Carl Beckett; 02-19-2022 at 9:05 AM.

  7. #52
    Quote Originally Posted by Phillip Mitchell View Post
    I guess it depends on your tolerance for searching... The transformer I found for $100 used (and professionally tested) would have been well over $1k to buy new on the spot, so you can see the value in searching for a few weeks for good condition used.
    I agree. I did my electrical upgrade and I purchased everything on eBay because I knew what parts I needed, and I waited. Over a few months, I bought everything, almost all new, at 50-70% off the electrical supplier price.

    What I was referencing above is a bit different. Let me give you another real-world example of some mental gymnastics.

    I am going to purchase a machine. There are two variants; one single-phase, one 3-phase with more "whatever" and I want the "more". So I start trying to figure out how to do the 3-Phase work. Well, I have a 3-Phase converter; great, I'm all set, except wait, it needs 480v. Great, I'll just buy a transformer, but it's $1800 news. That's a lot, but maybe it's worth it, or perhaps I can find something cheaper. Since it's 480-volt, though, I'm going to need double the amperage. Is my digital converter going to be enough to run my new machine AND the machine it was purchased for? Maybe I should buy a voltage doubling phase converter just for this; how much are those? How much will the installation be? Perhaps there is a cheaper option? Let me ask Wolf for help. A week later, I purchased the single-phase machine to hell with it because the "more" no longer sounds that appealing.

    The point is, if you know what you want, it's easy to wait for that good deal. However, if you are exploring a purchase and you get mired down in options, you are just as likely to buy nothing because all the research, pricing, investigation, and discussions are a colossal time suck. That's the mental gymnastics Erik speaks of.

  8. #53
    480v configuration uses half the amps of 240v. It’s all math figuring out if the converter, etc can handle a certain load. I suppose you could call that mental gymnastics; it’s just part of putting all the pieces together. I’m not sure what a voltage doubling phase converter is? Why not use a transformer?

    In my mind, if you’re going the RPC / digital converter route then it makes a whole lot of sense to size that converter up to the highest amperage capacity that you could imagine using and starting there. In my case it’s an RPC that puts out 30 amps at 220V 3 phase which can handle anything ~10 hp and below. This was not cost prohibitive to find used ($800 a few years back.) I can’t run a wide belt off of that but have no space for one anyway.

    No way that I would pay $1800 for a new transformer when there are so many used examples out there for ~ 25 % of new but that’s just me, I suppose.

    For me it all changed and opened up a lot of options once I found the 10HP RPC and brought it online. From there it’s pretty simple to assess what machines that come on to the radar are suitable choices or not. Before I had the RPC there was some confusion / stress about how I could make say, a 20” industrial planer work in my shop. This is the upside of committing to something like an RPC/etc that is sized for future “growth”. It really didn’t cost me that much to get it all in place and now the infrastructure is there and a known variable in the equation.
    Still waters run deep.

  9. #54
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    Quote Originally Posted by derek labian View Post
    The point is, if you know what you want, it's easy to wait for that good deal. However, if you are exploring a purchase and you get mired down in options, you are just as likely to buy nothing because all the research, pricing, investigation, and discussions are a colossal time suck. That's the mental gymnastics Erik speaks of.
    I'm a fan of less thinking /pre planning. Buy the equipment, then figure out how to make it work (or move it) after its in the shop. Doing it that way also motivates you to finish the process since you have a large dead machine in the way if you don't. It hasn't failed me so far.

    That is the reason I commented upthread that the mental gymnastics were the problem.

  10. #55
    Quote Originally Posted by Phillip Mitchell View Post
    480v configuration uses half the amps of 240v. It’s all math figuring out if the converter, etc can handle a certain load. I suppose you could call that mental gymnastics; it’s just part of putting all the pieces together. I’m not sure what a voltage doubling phase converter is? Why not use a transformer?
    I was referencing the additional wattage for an existing 240v phase converter, over a SP source. If you don't have the wattage available, a transformer isn't going to help. Voltage Doubling Phase Converter.

    Quote Originally Posted by Phillip Mitchell View Post
    No way that I would pay $1800 for a new transformer when there are so many used examples out there for ~ 25 % of new but that’s just me, I suppose.
    It was a story and I didn't buy new or used transformer. You are getting stuck on the details of the example and missing the bigger point about options, choices, and complexities leading to people walking away all together or just going SP.
    Last edited by derek labian; 02-19-2022 at 1:10 PM.

  11. #56
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    You all wear me out. It just ain’t that hard. I have a RPC wired into its own panel feeding multiple machines, a VFD wired into my Bridgeport which also provides soft start, reverse and variable speed. , and a static phase converter on the self from another shop.
    It’s just not that hard. Hire someone if it’s above your skills.
    The Plane Anarchist

  12. #57
    Quote Originally Posted by Leigh Betsch View Post
    You all wear me out. It just ain’t that hard. I have a RPC wired into its own panel feeding multiple machines, a VFD wired into my Bridgeport which also provides soft start, reverse and variable speed. , and a static phase converter on the self from another shop.
    It’s just not that hard. Hire someone if it’s above your skills.
    This is what I’ve been saying from the beginning, just in more (too many?) words.

    The point I was trying to make is that there is a lot of information out there to solve the specific needs/problems you may have with phase and/or voltage conversion and anyone can do it and have a 3 phase capable shop with some combination of time, money and sweat equity depending on what you have more of to spare. It really isn’t as complicated as you might be led to believe.
    Last edited by Phillip Mitchell; 02-19-2022 at 4:39 PM.
    Still waters run deep.

  13. #58
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    Quote Originally Posted by Phillip Mitchell View Post
    This is what I’ve been saying from the beginning, just in more (too many?) words.

    The point I was trying to make is that there is a lot of information out there to solve the specific needs/problems you may have with phase and/or voltage conversion and anyone can do it and have a 3 phase capable shop with some combination of time, money and sweat equity depending on what you have more of to spare. It really isn’t as complicated as you might be led to believe.
    Yes, Exactly
    The Plane Anarchist

  14. #59
    First is thanks to some help from Phillip Mitchell I've gotten an American Rotary AR-20 up and running several 3ph machines via a 3ph load center.

    Here's my quick question:

    I got the AR-20 as it is rated for 10hp machines, such as the 7.35kw Felder slider I picked up. However can it start and run two machines that exceed it's 10hp rating?

    Datasheet is here:

    https://www.americanrotary.com/pdfviewer/?pdf=3322

    max starting current: 28amps/10hp
    max running current: 56amps/20hp

    Can I start and run that 24amp Felder saw and a 7amp/3hp dust collector off the same AR-20? Or should I think about a vfd on a 220v line for the DC?

  15. #60
    Hey Nick,

    Good to hear from you and glad you got your 3 phase sorted out. I would tend to think that you could run those loads based on the amps. How many single phase 240v amps are coming in to the RPC?

    The DC will probably be close to that 7 amp rating consistently, but beyond starting in-rush current and really heavy ripping, for example, I don’t see the saw pulling 24 amps continuously. If it doesn’t work and isn’t quite enough then a 3HP VFD is cheap enough to add on.

    I would imagine you will be fine, though. I don’t really run multiple 3 PH motors simultaneously in my shop (DC is single phase) except a shaper and power feeder, but I have read of folks using their RPC as follows to start a harder to start motor that may be close to the capacity of the RPC - start the smaller motor first with the RPC. Then, after that’s running start the larger motor and the smaller motor already running can actually help the RPC start the more difficult load. It’s certainly worth a try and I’d imagine it would handle it fine if you have 60 amps Single phase incoming / 30 amps 3 phase output.
    Still waters run deep.

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