3 machine's RPC or VFD's ? NEED HELP!

I have looked at alot of info on this forum and while I am much more educated than I was before I would still like some input. I am kinda on the fence on whether to go with a RPC or a VFD's for my set-up, I can see benefits with the VFD that I sure like. My problem is the room I built for my machines I wired for a RPC before understanding VFD's so with that said before I go any farther here is my machine list.

#1 Clausing Cochester 16spd Lathe 2spd 5/2.5HP 3ph 13/13.5amp continuous torque motor no clutch

#2 Birmingham 16spd mil 2spd 3HP 3ph 6/5.6amp motor

#3 Powermatic 20" bandsaw 1.5HP 3ph 5amp motor with model 600 blade welder that is wired in the machine 230v single phase (form the factory)

SO NOW WIRING
I have #4 wires running from a single phase 125 amp box to across the room which is 8FT wide to where the RPC controller would be and beside that is a 3phase 6 breaker box for distribution to the machines. If I go RPC I will just leave this be. If I go VFD I would change the 3 phase box out with a single phase box and power it with the #4 wires from the 125 amp box and have the VFD's at the machines. What I don't know is if my wires going out to the machines are big enough for the VFD's. I might of messed this one up as well with the RPC? Going out to the lathe which is about 15FT I ran #8 wire, to the mill I ran #12 wire which is 6 Ft away and #12 wire to a band saw that is about 10FT away. By what I have read on Hitachi web site I need #6 ran to the lathe to control the VFD and need # 10 ran to the mill. If I go the VFD route I would convert the band saw to single phase with a motor swap. I notice that the non-vector VFD shows #8 wire to be fine but the vector VFD shows #6 wire is needed. (Hitachi shows both #6&#8 use 40amp breaker) vector and non-vector show the # 12 wire to the mill needs to be #10. Here are the VFD and the RPC's I have looked at.

VFD for lathe
X200-055LFU XVT2-75
WJ200-055LF PWV2-75

VFD for mill
X200-022NFU XVT2-30
WJ200-022SF PWV2-30-1

RPC For everything
American Rotary 15HP Rotary Phase Converter | Phase Converters | American Rotary
15HP Rotary Phase Converter

I might add that I am not much interested in building a RPC not that I don't think I could build one or that a home built one is bad. Im just saying If I go RPC I would like one that started with a push of a button and it have a soft start rating. I don't think I could build one that comes close to a soft start rating with out pony starting which I don't really want.

I value any and all suggestions and if something doesn't sound right please inform me I am not a electrician so my wiring could be far from right. Like I said Im not sure it is right even with an RPC after reading more info. I read somewhere that the wires going from the RPC to the different machines should all be sized the same as the biggest motor wire size which doesn't sound right to me. Because what if your biggest motor is 5HP and down the road you add a 7.5 you wouldn't want to rewire all of your machine just cause the 7.5 motor needs bigger wire. (RIGHT?)

Again this is how I have it #4 to the RPC controller #6 to the idler #6 to the 3phase breaker box, # 8 to the lathe #12 to the mill and # 12 to the band saw.

I'm not opposed to staying with my first thought of going RPC which might be the right choice with what I have and any future machines.

New member by the way if you couldn't already tell! LOL (First POST!)

Let me see If I understand this right! If I want to run my 5 hp lathe from a VFD I would need a 10 hp 3 phase VFD. That means when ran off single phase it would be derated to now be 5 hp. By saying that I understand it takes 1.73 single phase amps to make 1 amp of 3ph which means to me if a 10hp VFD is rated at 32 input amps I would need to supply it with a little over 55 single phase amps to it. (RIGHT!) I would then need to run #6 wire to the VFD which means the #8 that is already ran is not going to cut-it. I have read from this forum and others for hours/days on end now and must say I have learned allot but it is still not clear as water to me. About the time I think I found a good thread with the info I need it changes subjects or the important stuff get PMed to whoever started the thread. I hope someone here will post some info I would greatly appreciate the help from someone with knowledge on what I am trying to do. I like the sound of a VFD but the further I go the more trouble it looks for what I’ve got and that it may be better just staying with my first plan and go RPC.

383,

I'm not one of the whizzards here. But generally, they seem to be in agreement on this maxim: "If you want to run a 3 phase machine buy a VFD. If you want to run a 3 phase machine shop buy (or build) an RPC."

Also, I believe you're right about derating VFDs. The problem is that single phase input VFDs seem to stop at 3 hp. Anything bigger is designed for 3 phase inputs. Some (but not all) of these will run on single phase inputs but you do indeed have to derate them by half (or so I'm told).

I've never explored the idea here, but I am under the impression that VFDs are worth having and using, even if you HAVE 3 phase. And of course, if you don't, they're the cat's meow. So this leads me to consider that it might be a viable plan to run a VFD from an RPC and have the best of both worlds. That's a question I've never asked but I'd be surprised to learn that nobody has discussed it here, as they've pretty much chewed over every electrical problem or concept in the galaxy or beyond, from a minimum of "several times" to "so many times they get grumpy when somebody brings it up yet again".

As to your second inquiry about calculating the single phase amps it takes to run a derated 3 phase VFD I won't go there because I'm not competent to do so. But your calculation SOUNDS about right to me.

Best of luck.

Vernon

383FormulaS said:

1) Let me see If I understand this right! If I want to run my 5 hp lathe from a VFD I would need a 10 hp 3 phase VFD.

2) That means when ran off single phase it would be derated to now be 5 hp. By saying that I understand it takes 1.73 single phase amps to make 1 amp of 3ph

3) which means to me if a 10hp VFD is rated at 32 input amps I would need to supply it with a little over 55 single phase amps to it. (RIGHT!)

4) I would then need to run #6 wire to the VFD which means the #8 that is already ran is not going to cut-it.

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all good questions! I numbered 'em for replies I would make....

1) yep! A bit of a side issue is that a lot of hitachi vfds that we sell/distribute are rated both constant torque (CT) & variable torque (VT). the VT rating is typically 1.5x higher than the CT rating.... confusing, but just know that YOU want a vfd capable of CT.... so thee drives rated 7.5hp CT are also rated 10hp VT.... bottom line means you can save a little money and buy the 7.5hp CT (10hp VT) rated drive instead of needing to buy the full 10hp model from someone else......

2) yep!

3) nope! this misses the point..... and yet makes it clearly too! IF that 10hp drive rated 35 input amps, that means you should not go over 35 amps! make sense? so you cannot put 55amps into it 1ph our you are overloading input! see THAT is why a 10hp drive gets derated to 5hp! the 5hp version is rated probably 18 amps..... now do your 1.73x and you see that you will be pulling only 33 or so amps -- from the 10hp drive rated 35amp max input!!! bingo, all are happy

4) so see that you still have your 5hp motor that can is only rated what, 16 amps (guess)? so 16*1.73= (no calculator) 28 amps SINGLE PHASE INPUT PULL - not 55. so if your wire is good for this then you are good to go! I am not vouching for code, just ratings. please take your motors nameplate amps *1.73, add a couple percent for efficiency, and then double check that your wire, cb, etc, is ok for that - I am not a code wizard by any means.

looks like another similar answer post came in while I was typing mine.

Sure wish the owners of this forum could get the clock to be more than a random number generator so it is obvious when two posts come in at the same second......

Way overkill on the RPC there. 10hp RPC should have no trouble running any or all of these machines, as long as you don't try to start all simultaneously (and what would be the point in that?). You can probably work with a 7.5hp converter if you build your own and tune it properly, but since you don't want to do that, better to double the converter to be on the safe side. If not for your unclutched lathe, you could get by with a 5hp converter.

Not sure why the desire for a "soft start" RPC idler. A 10hp RPC kicking on is no worse than a 4ton AC unit. Your service is never going to know the difference. Only time to go9 soft start on soimething like that is when you are trying to reduce start shock to something like a long staged lineshaft pump or something that is so big a hard start is going to require massively over-sizeing the line side (400hp motor or the like).

I think most here are missing a major issue: The lathe and the mill are TWO SPEED motors with different current ratings for the two speeds. To use the VFD on these motors, you will have to disable the two speed function for two reasons, one, switching the load post-VFD is a no-no and two, to avail yourself of the VFD's circuit protection features you will need to enter new paramaters whenver you want to go from one speed to another.

This is a textbook example of where the RPC will shine. Multiple motors, multiple speed motors, and complex switching (for the multi-speeds) are NO issue at all for the RPC, but will pose headaches (and expense) with the multiple VFD's. Keep life simple, build/buy the RPC and be happy. And you are even wired for the RPC! btw, Mike C. is spot-on (as usual) above. A 7.5 HP RPC should be fine for your machines, at least most of the time. Starting the lathe at higher spindle speeds and/or with a big workpiece and/or in a cold shop could cause starting problems. If you foresee these situations as not applying to you or if so only occasionally, you may be able to get by by starting the RPC, then starting the mill (or bandsaw) and only then starting the lathe. The additional motor acts as a de facto helper RPC and can be turned-off once the lathe is up to speed. If you are in doubt, go with the 10HP size.

Steve

Breaker breaker:

Can I trouble you for some insight as to how someone in "The Panhandle of Texas" has a screen name of "383FormulaS" ???


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I am Ox and I approve this h'yah question!

sa100 said:

I think most here are missing a major issue: The lathe and the mill are TWO SPEED motors with different current ratings for the two speeds. To use the VFD on these motors, you will have to disable the two speed function for two reasons, one, switching the load post-VFD is a no-no and two, to avail yourself of the VFD's circuit protection features you will need to enter new paramaters whenver you want to go from one speed to another.

This is a textbook example of where the RPC will shine.
Steve

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good points in your post Steve. rpc is simple solution. but I think maybe your major issue point is overblown some...... yes, a two speed motor has 2 configurations, two hp's, two current ratings maybe.... so what 99.9999% of folks with these motor do is simply wire them to the LOWER speed setting and be done with it. the benefits of the vfd bring them back to the same highest hp capability the motor is capable of thru its ability to go over base speed. so it really is not a major issue.

that said, perhaps an rpc IS the best solution with 3 different machines and your other points back it too! but everyone loves variable speed capability offered by the vfd..... pros and cons.

Mopar fan! Have a few 1 just happens to be a 68 Barracuda 383 Formula S 1of 99

Ox said:

Breaker breaker:

Can I trouble you for some insight as to how someone in "The Panhandle of Texas" has a screen name of "383FormulaS" ???


--------------

I am Ox and I approve this h'yah question!

Click to expand...

Alot of good points rolling in! I am so glad for you guy that have input to share. One thing that I would like about the VFD setup is that I could just walk up to a machine and turn it on unlike starting a RPC and then starting the machine. My machining sessions will mostly be sort/unplanned spur of the moment so I really wouldn't leave a RPC running for 8 hrs a day. My main hobby is building cars and the machines are going to be there when I am needing them. The wiring on the machine I'm not to worried about if going VFD the mill looks quit simple, the hardest thing I can see on the lathe would be trying to make the complicated drum switch tell the VFD what to do ( or maybe retrofit a simpler switch). I have no problem staying RPC but with what I am doing It could need to be started multiple times a day rather then running all day. (((that is why I was looking for one with a soft start rating to keep inrush down to a minimum))) Maybe I am looking at this wrong but it seems a VFD would use less electricity than multiple stars on a RPC I don't think I would mind leaving a VFD on most of the day but leaving a RPC running all day seems wasteful especially if you might not need it anymore that day.



Also the reason behind a 15HP RPC is that I have came across a few threads on here where people are having problem starting 2 spd motors and that a RPC should be 3X the HP rating of a 2 speed motor. There is probley more to this then what I know but what I do know is I don't want this to be me.

383FormulaS said:

Mopar fan! Have a few 1 just happens to be a 68 Barracuda 383 Formula S 1of 99

Click to expand...

Never heard of that (?) option package before.


In my world, a 383 Formula S is a beginners SkiDoo snowmobile from the mid/late 90's.
(known to have nice seat covers.)





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Sweating to the oldies!
Ox

I see not much use for a snowmobile in my area. lol
I would post a pic but it wouldn't let me but mine is more like a 1968 muscle car.

Only thing that might need 3x on a converter is an air compressor or huge grinder with a wheel that has to be brought up to speed over several seconds with a huge inertial load. I am speaking from experience in my ratings. I have a home built 5hp converter. It runs everything from my 1/4hp tool and cutter grinder to my 5hp (clutched) lathe. Included in this are three 3hp motors, one 1200rpm, one 1750rpm and one 3450rpm. No problem starting any of them at any spindle speed.

As for start/stop on a converter consuming power, you are worrying a lot about nothing. With my converter, lathe, mill, grinders, whatever running a dozen or so hours per month working on a project, I cannot tell any difference in my power bill over just running the lights and beer fridge (1942 GE). Another advantage over a VFD is that you can now buy ANY piece of 3 phase equipment that comes your way and not have to buy another VFD to drive it. I currently have 9 machines with a total of 14 motors in my shop. Motors range from 1/8hp to 5hp, all run off my converter.

If you wanted to be able to stop/start your converter as you work, you could hook up a wireless remote like this to the control circuit...

Amazon.com: New Indoor Wireless Remote Control Power Switch Outlet: Electronics

If I could get by with a 10 HP RPC that would be great!

So is there nothing to the 2 spd motor problem like I have read or is that just on some motors?

Also would my #4 wire feeding my RPC be overkill for a 10 HP?

If you look at the manuals on American Rotary's website, they list 8 awg on the single phase input of a 10HP unit. I used a 60A breaker and 6 awg on mine.

Dang that's what I figured! I ran the #4 already because I was planing on a 15 HP RPC and went the next wire size up plus I already had the wire so I used it. Oh and yes #4 is a pain to work with.

thermite said:

#8 is probably a modest overkill for your planned use, but may be needed for code compliance.

It isn't ALWAYS good to meet, then exceed code. Sometimes overbuilding just opens a new can of costly worms. Breaker and disconnect costs - even upstream load-center upgrade, for example, not just a few extra bucks for wire.

And have you ever tried to simply pull - and most of all, TERMINATE multiple conductors of #4 or above in the space available?

Bill

Click to expand...

thermite said:

At the very least, I'd terminate it in a proper load-center, THEN use quality breakers, dedicated disconnect, and such off of that to the VFD and machinery.

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That is what I had in plan if I went VFD's this would still have all my machines in one load center whether they run off 3 phase or 1 phase.

thermite said:

Nothing like 4-ought, but ... I'd actually pull that #4 back out and go sensible rather than have to uprate the rest of the gear to keep it in code. An inspector takes the very reasonable position that if you have #4, you have to switch and protect accordingly, 'coz if YOU won't do something stupid, the next guy who owns the place - or some poor sod doing carpentry repair along its route - WILL DO.

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If you are going to have it inspected, may be better to have it (inspection) done BEFORE you spend the work and money to remove the #4 as it apparently is NOT out of code to use oversize wire. apparently inspector playing 'what-if' scenarios is not code. Proof from the code wizards:

20a breaker protecting #8 wire

OK, if you say 'so'.