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  1. #1
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    Default LTB 3 phase converter.

    I'm interested in a three phase converter, sufficient to run a Bridgeport type mill. Figures out to be about three horsepower. I'm NOT what you would call "electrically fluent" so bear with me. I've talked to Phase Perfect, and intend to (eventually) bring in a small lathe, but that may be a while. They seemed fixated on running both machines on one converter, which would have definite advantages, but I haven't even found what I want in the lathe department, so I feel that's jumping the gun a bit. I'm not ready to spend the $10K they were talking either. This is a retirement shop at home. Out in the country. My REC flat will not discuss running three phase to my house, and if they did, the price would put it out of reach, so I'm locked in to a converter. Anybody got anything? Apparently I just missed one that would have been perfect.

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    To run multiple machines with their original controls intact something like this will do; Standard Series .

    To get more control, ie variable speed, a VFD is a good choice. There are many vendors in the $300 and less price range for 3HP. I have Automation direct, GE, Hitachi and others.

    While Phase Perfect makes excellent equipment their stuff is quite expensive for an occasional use shop.

    I went the VFD route and simply added one when needed. If I were to begin again with all machines at one time I still would want VFDs simply for speed control.


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    Quote Originally Posted by WHHJR;31
    24788
    To run multiple machines with their original controls intact something like this will do; Standard Series .
    Plus a 3-phase motor of a suitable size to make RPC (rotary phase converter) out of those static converters.

    Static one works "as is" too, but the mill will become less powerful.

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    The mill I have has a vary drive in the head, so I really don't need variable speed. The lathes I've been looking at all have transmissions, with multiple speeds built in, so I really don't see the advantage there either. I haven't looked into a VFD. Just trying to get my head around a 3 phase converter is proving to be a steep curve. I have heard that the rotary phase converters end up reducing the power of the tool they are used on, so I'm a bit skeptical of that. I don't need much, but three horses really isn't much.
    And yes, while they come highly recommended, the Phase Perfect converters appear to be out of my current price range.

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    Static phase converters reduce the power at the motor, rotaries do not. For a small home shop I would use a rotary, and they are not too difficult to make. There are also control boxes where all you need to do is supply a 3 phase motor. I will be back in central Texas in a few weeks, if you need help sourcing an inexpensive 3 ph motor let me know, I see oodles of them.

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    VFD is the way to go in my opinion, even if you donít care about the speed change ability, more cost effective as you donít have to run an extra motor to generate your third leg and you get true three phase to your motor, unlike the ď manufactured ď phase from a converter ... my 2 cents ,, I have 8 three phase machines and I use the drives strictly for phase conversion...


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    Quote Originally Posted by Raybmarlow View Post
    VFD is the way to go in my opinion, even if you don’t care about the speed change ability, more cost effective as you don’t have to run an extra motor to generate your third leg and you get true three phase to your motor, unlike the “ manufactured “ phase from a converter ... my 2 cents ,, I have 8 three phase machines and I use the drives strictly for phase conversion...


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    Purchasing eight VFDs is more cost effective than getting one RPC? I have a doubt.

    I'd understand this approach if you needed them for speed control in addition to 3PH conversion.

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    Default Speed control

    I was using my Monarch 12CK today to make some short rods with the ends drilled and tapped. Facing and drilling were done at 100% speed and the tap was run at about 20%. No gear changes needed just speed control and motor reverse. With that lathe it just works. With most drives if you set up a forward/reverse switch and 5 second (or so) speed ramp you get a nice nearly instant reverse.

    I do the same type power tap operation on the Knee Mill when needed.


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    Quote Originally Posted by MichaelP View Post
    Purchasing eight VFDs is more cost effective than getting one RPC? I have a doubt.

    I'd understand this approach if you needed them for speed control in addition to 3PH conversion.
    Yes I would say it is more cost effective, no insult intended sir,, the things not taken into consideration... Running two motors to power one, twice the electricity, 80% duty on the motor being run, premature failure and BP motors aren't standard so more expensive, the 8 VFD' s I have were bought right , less than 1000.00 invested, to me , that's a better way to go, as I said in my initial post, just my 2 cents or opinion, this may not work for everyone, but works for me .. but we are discussing 1 Bridgeport here not my 8 and for argument purpose, I will sell this gentleman one, brand new for a far less cheaper price than a RFC and he will save in the long run .... 2 more cents worth .. LTB 3 phase converter.


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    Quote Originally Posted by Raybmarlow View Post
    ...twice the electricity, 80% duty on the motor being run, premature failure...
    I could argue with every point here, but I'll not. To each his own, I guess. If you were able to obtain all VFDs inexpensively (yet without quality issues), then I can see your point, of course.

    Naturally, if this BP is the only machine, then a small VFD would be the way to go. But if more 3ph machinery is expected to follow (and we rarely see home shop machinists staying with one or two machines), then going the VFD route (unless dirt cheap) will need a more serious justification than a simple need for phase conversion. IMHO, of course.
    Last edited by MichaelP; 02-12-2018 at 10:55 PM.

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    Too big for what you want, but you might want something to power a big lathe later. Nice unit I don’t think he has sold it yet. For sale 20 hp RPC

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    The one thing about VFDs is that they do not want switches, relays, etc. between the motor and the VFD as it tends to blow the VFD up. So it you are interfacing to a single speed Mill motor it is pretty easy. If you are trying to put it on a lathe with a 2 speed motor, relay controls for forward/backward, and a separate 3 phase coolant pump - it is an issue. Not that you cannot wire around all the existing controls, but it is a job and some functionality can be lost (pick 1 speed for your 2 speed motor). In that case a rotary phase converter is a lot easier - just plug it in to the lathe and use the existing lathe controls.

    Maybe it is just me but the high pitch whine of the VFD is also annoying.

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    Quote Originally Posted by dalmatiangirl61 View Post
    Static phase converters reduce the power at the motor, rotaries do not. For a small home shop I would use a rotary, and they are not too difficult to make. There are also control boxes where all you need to do is supply a 3 phase motor. I will be back in central Texas in a few weeks, if you need help sourcing an inexpensive 3 ph motor let me know, I see oodles of them.
    Good to know. I'm far from fluent in electrical issues. This little tidbit could have been an expensive mistake.
    On another related note, should I "overbuild" my system with a bigger RPC than what it appears to call for? Like ,say a five horse RPC for that three horse mill? Or just go with the three horse RPC? I'm leaning more in that direction. Looked a Phase Perfect, but the budget just won't stand that.

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    Quote Originally Posted by gorrilla View Post
    Good to know. I'm far from fluent in electrical issues. This little tidbit could have been an expensive mistake.
    On another related note, should I "overbuild" my system with a bigger RPC than what it appears to call for? Like ,say a five horse RPC for that three horse mill? Or just go with the three horse RPC? I'm leaning more in that direction. Looked a Phase Perfect, but the budget just won't stand that.
    Sure you can. And that's exactly what I'd suggest to avoid replacing your RPC when you buy more machinery. Just get one suitable for the most powerful machine you may buy later. For example, I have a 15hp RPC while my most powerful lathe is 7.5hp (in reality, a 10hp RPC would handle my current needs, but I always prefer to have more leeway). Naturally, higher HP idler motors consume more power and require heavier wiring/breaker.

    And choose an RPC with a low rpm idler motor: they're significantly less noisy. When I started, for a short time I had a 3600rpm Baldor (5hp), and it was unbearable in terms of noise even when it was next door. Now I run a large 1150 rpm motor (15hp), and it's whisper quiet. I bought this old behemoth from a local motor shop for $150 or so.

    If you go this route (buying motor and control box separately) and choose a really low rpm heavy motor like mine, report its stats to those who make your control box: they may need to make some changes to the capacitor values. I bought my control box from a small East Coast engineering company. They did excellent job, and the price was very reasonable. If you need their contact info, send me a PM or e-mail on the weekend, and I'll try to find it. Hopefully, they're still around.
    Last edited by MichaelP; 02-14-2018 at 01:49 PM.

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    I would look on craigslist before I bought new. I see lots of them on craigslist in Texas - not sure if any are close to you. If that doesn't work for any reason, I would go with wny, nice product at VERY reasonable prices. Just get yourself a motor and hook it to his panel and your ready to go. If I was in your shoes and looking at powering up a hobby/retirement shop, I would go with a 10 or 15 hp unit. That would probably be sufficient for whatever you're going to need.

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    I think he is on vacation for a bit, but this is by far the easiest route for multiple machines. I have a 15hp that runs everything in my shop, from grinders to a cnc mill. Just buy the panel, supply with 240V power, connect to the idler 3 phase motor and have full 3 phase power out. He can provide basically any combo you need, motor size and/or RPM (17XX or 34XX). I have purchased several from him over the years as I've upgraded and sent even more people his way that are satisfied. This is a listing for a 7.5 idler, but he sells everything.

    Phase-Craft 7.5 HP ROTARY PHASE CONVERTER CONTROL PANEL manual start-pushbutton! | eBay

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    I would disagree with just about everything that Raybmarlow said in post #9. I have built several rotary phase converters and have been running a shop on on a phase converter for twenty years without any trouble. The static VFD's are fine if you need variable speeds, otherwise no. Go to the sub-forum, Transformers, Phase converters and VFD, here on Practicalmachinist for phase converters and do some reading.

    JH

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    Quote Originally Posted by James H Clark View Post
    I would disagree with just about everything that Raybmarlow said in post #9. I have built several rotary phase converters and have been running a shop on on a phase converter for twenty years without any trouble. The static VFD's are fine if you need variable speeds, otherwise no. Go to the sub-forum, Transformers, Phase converters and VFD, here on Practicalmachinist for phase converters and do some reading.

    JH
    Jim, itís ok that you disagree, Iím ok with that, I stated that VFDís work for me, I have a friend, he has been, running his entire shop off a home made rotary converter for 20 plus years, never had a problem, I have been running my shop almost 20 yrs on VFDís with no problem, I even use 3 phase in to 3 phase out , something everyone tells me that you canít do, itís worked for almost 20 years, so I need not read , Iíll make choice out of fact ...as I said in my post that you disagree with this is my opinion and what works for me ... and has worked for me for quite some time and RPCís work also, itís a matter of preference, I believe VFDís are more effective with true 3 phase , everything can be argued as people want to be right , I donít need to be right, I do what works for me, Iím sure either will work for the gentleman that started this thread , he was asking for input, I shared mine, right or wrong in anyoneís view ... I am sure you will disagree with this also.. thatís ok LTB 3 phase converter.


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    Quote Originally Posted by Raybmarlow View Post
    Jim, it’s ok that you disagree, I’m ok with that, I stated that VFD’s work for me, I have a friend, he has been, running his entire shop off a home made rotary converter for 20 plus years, never had a problem, I have been running my shop almost 20 yrs on VFD’s with no problem, I even use 3 phase in to 3 phase out , something everyone tells me that you can’t do, it’s worked for almost 20 years, so I need not read , I’ll make choice out of fact ...as I said in my post that you disagree with this is my opinion and what works for me ... and has worked for me for quite some time and RPC’s work also, it’s a matter of preference, I believe VFD’s are more effective with true 3 phase , everything can be argued as people want to be right , I don’t need to be right, I do what works for me, I’m sure either will work for the gentleman that started this thread , he was asking for input, I shared mine, right or wrong in anyone’s view ... I am sure you will disagree with this also.. that’s ok LTB 3 phase converter.


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    Ray: I don't disagree with this post. You make some some excellent points and I agree that you should offer up your experiences and views as in post 9. That is what this forum is all about. We all learn from each other's views. Thanks.
    JH

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    Quote Originally Posted by James H Clark View Post
    Ray: I don't disagree with this post. You make some some excellent points and I agree that you should offer up your experiences and views as in post 9. That is what this forum is all about. We all learn from each other's views. Thanks.
    JH
    Respect is what drives us all forward ...


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