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kyfho
12-31-2009, 05:03 PM
Hi folks. I'm in a bit of a dilemma here and could use some suggestions.

I'm starting out with a 1967 BP with 1 HP 3 phase and was planning to buy a small VFD to run it.

I am about to be the recipient of a really nice collection of machinery. My BIL has a customer (manufacturing) that is getting rid of a lot of their older maintenance equipment (they're changing locations) and it looks like I can get the stuff for pennies on the dollar, well under scrap iron prices. Too good of a deal to pass up.

I am looking at adding a lathe, horizontal band saw, vertical band saw, cold saw, hydraulic press, and a surface grinder. I haven't seen the stuff yet, but everything is supposed to be in decent, running condition.

Problem is that everything is 3-phase and I really wasn't looking to put VFDs on all the equipment. I have a new 5 HP, 3-phase motor I bought surplus from my company a while back and was wondering about the feasability to build a rotary converter from it and have a dedicated 3-phase circuit in my shop.

Hobby shop only and so I will probably only be running 1 machine at a time, maybe 2 if I've got something on the surface grinder and want to run the mill while I wait for that to finish.

Any suggestions would be VERY helpful.

Will post pictures and details as I get the equipment. I've got several trailers full to go get.

JoeFin
12-31-2009, 05:11 PM
Sounds like a really good reason to build a 3 phase distribution, althou it might better be served by a slightly larger 3 phase generator then a 5 hp motor

Mcgyver
12-31-2009, 05:18 PM
sounds like quite the score....build your own RPC with that motor. Lots of guys will tell the benefits of VFD's but i went RPC because i didn't want to buy many VFD's as machines are added. Seven 3 phase machines currently. the variable speed advantage of vfd is there I guess, I've never missed it as each machine as an adequate range via their gearboxes....I need a vfd for the monarch though but will input 3 phase into it so i don't need as large VFD

you'll get opinions on both, but with a motor in hand vs half a dozen VFD's isn't the decision already (mostly) made?

Boucher
12-31-2009, 05:24 PM
My shop is a one person home shop also. My Roto-Phase says max motor size is 3 hp max. Total load 9 hp max. It works very satisfactory. I never run the Mill and the Lathe at the same time, but I could. From a functional standpoint the Power saw is the most likely to be run with something else. Sounds like you gat a super good deal on the machines.

Bill in Ky
12-31-2009, 05:49 PM
The first one I used was a 3hp 3phase motor to pull a 1 1/2hp BP. I wired it up, wound a rope around the shaft, gave it a pull, then hit the power...Presto
3 phase power to my Bridgeport.
Yep, I'm a redneck. d:^)

rdfeil
12-31-2009, 05:49 PM
I am a huge fan of VFDs, but your application is the perfect example for rotary converters. I would take the above suggestion and wire the shop for three phase distribution. The only thing to consider is the size of the motors on the machines and size the rotary accordingly. Another thing to keep in mind is that many machines really don't benefit from variable speed (saws, shapers, surface grinders etc), while the lathe and milling machine would benefit and you always can add VFDs to those machines when the need and funds permit ;) . If you already have three phase power from the RPC then the vfds can simply be added with no concern about single phase input. This may save a few bucks in the future.

Robin

Rich Carlstedt
12-31-2009, 06:12 PM
Can't beat a rotary converter for YOUR application.
Check the HP of the other equipment.
5 HP is overkill and will waste energy UNLESS one of the
machines has a 2 speed motor.
If they all are 1 .5 HP or less, I would go with a 3 HP to reduce noise and
electric bills.
If you decide to use the 5 HP unit, by kicking the shaft to start
You will not need the capacitors either, Although they do help
Kicking over the shaft and powering up, is the absolute simplest and cheapest way to get 3 phase in the shop

Rich

JoeFin
12-31-2009, 06:13 PM
Let me explain myself why I suggested a slightly larger motor for the 3 phase generator

I have a 7 1/2 hp Ronk Rotophase. Its a good unit and I can run multiple machines on it with ease. The problem is "Starting Current". My cnc mill has a relatively small motor at 2 hp, but when it starts you can hear the rotophase grown under the "Starting Load". Which as you know can be 400-700% of motor load.

Other then that the 71/2hp unit works flawlessly and has been doing so for years

lakeside53
12-31-2009, 07:04 PM
I was in the same dilema.., 5 VFDS, more machines appearing... have a nice 5hp rotary converter - but it won't run my 4hp lathe in the upper two speeds - the lathe motor starter will thermally trip because it's taking too long to spool up.

So... screw it - I'm putting in a 15 hp converter, three phase distribution, and some of the larger VFD's will be run from the three phase (oh... easy to buy used or new "cheaper" larger vfds that are three phase..). In addition to speed control, VFD's also provide excellent soft-start and motor protection (if programmed correctly)...

Single phase -> three phase -> VFD... Inefficient? Don't care...:D

Carld
12-31-2009, 07:22 PM
You have found a gold mine there. Your right in that since your a one man shop you only need an RPC and even if you run 2 or 3 machines the 5 hp RPC will run them.

This is the wiring diagram for my RPC and I have been using it for over 15 years. The VFD's are only needed if you want to vary the rpm of the motor and can only be used on one machine at a time as you well know.

http://i82.photobucket.com/albums/j276/yeathatshim/RPCwiringcopy.jpg

Jim Shaper
12-31-2009, 08:35 PM
I'd be looking at a vfd powered motor-generator, but then again I'm biased to that route because I took it.

Total cost for 24hp output capacity of TRUE BALANCED 3 phase was $1800; with the advantage of running the whole works off a 98% efficient vfd.

Of course I did it because I needed the phase angles to be perfect for the servo drives on my turning center, but it does make for a good solid power source for anything else down the road.

Doc Nickel
12-31-2009, 08:47 PM
Ditto most of the above.

I found myself in the same situation: I started out with one 3-phase machine, a small lathe that I bought already converted with a VFD. I'd already known of them before that, but this was my first hands-on example of just how handy they are, especially on a lathe.

Shortly thereafter I picked up a small horizontal mill that came with a 3-phase motor, and moreover, was one of a unique configuration that would have been troublesome to replace with a more common frame-size single phase. So I bought another VFD for it.

Before that one was done, I lucked into a large (12"x2" 2HP) pedestal grinder for fifty bucks. Also 3Ph, so I bought a third VFD. Then shortly after that, I bought an older Wells bandsaw- again, 3ph, and with an oddball motor mounting that would have made it difficult to swap.

I was starting to run out of money to buy VFDs. :D

The tipping point came when I decided to convert my other lathe to 3-phase (to get the speed control and additional torque, mainly) and then at about the same time, happened across a nice surface grinder. The grinder included a vacuum/coolant module, so had three 3-phase motors all by itself. That would have been some $700 just in VFDs...

So I wound up using one of the VFDs I already had, which I'd been using as as sort of portable power source for the pedestal grinder and the saw, and put it in the lathe.

Then I bought an American Rotary prefab control box- it was everything but the idler motor, and ran $225. Yes, a good scrounger can assemble an RPC for less, but I had no stash of caps and I'm not what you'd call electrically inclined. It was worth the cost to me to have a tested, ready-to-go, and better yet, warrantied controller.

I wired it up using one of the two 5HP motors I had laying around, and now I use it to power the pedestal grinder, the surface grinder (and it's vac module) and the bandsaw. It works great, easy to use, no problems.

The 5HP idler gives me something like 3HP of capacity, which is plenty for any one or even two machines. But as others have mentioned, I'm also a one-man shop, so it's rare that any two RPC-fed machines will even be on at the same time, let alone drawing anything close to full-load amperage.

So that's the solution I'd recommend: Put a VFD on the machines that can best use the VFD features- namely mills and lathes. Then put together one fair-sized RPC setup, and use it to run the machines that don't necessarily need variable speed, or programmable ramp-up/ramp-down, etc., like the cold saw, hydraulic press and surface grinder.

I'm just using cords and a single wall outlet for my RPC. All the machines it feeds are in the same corner of the shop, and two of them are immobile. Short lengths of cord were cheaper and simpler than running conduit past doors and around other fixtures.

But if you're industrious, running dedicated wiring, junctions and outlets is pretty easy.

Doc.

bob308
12-31-2009, 08:48 PM
the way we did it in my shop was to build a rotory phase converter ran that to a 3 phase breaker box then wired the machines like a 3 ph system. that way if i ever bite the bullet and get 3ph all i have to do is hook it into the panel box and i am good to go.

whitis
12-31-2009, 11:31 PM
How many machines can you operate at one time? If they are manual machines, that number may be close to 1. Which means that one VFD could run all the machines and give them all the benefit of variable speed.
It is a trade off between cost and convenience and depends on your usage patterns, etc.

There are a few issues, though.

Parameter sets: if you don't use the same parameters for each machine, you need multiple parameter sets. Some VFDs can do this. Baldor is an example. A computer can also reprogram a VFD with a communications port. Many of the parameters you might change from motor to motor are for protection or tuning that a rotary phase convertor isn't going to offer; others, like PID settings could depend on what motor you are driving especially with different sized motors. Some can change the PID parameters based on external input, even when other parameters can't.

Distribution: Longer wires between VFD and motor can increase voltage spikes. Stubs distributing power to unused machines may also. In a small shop, though the distances may not be too bad.

Control: if the VFD is centrally located, you need to go to that location to control or have a remote head.

Safety: there can be some unintended consequences depending on the wiring configuration you use.

One option is to carry or wheel the VFD from machine to machine, plug it in and plug the machine into it. If you move work between machines a lot, this is a pain but if you spend a lot of time on one machine between changes, not so big a deal. Another is to wire a remote head (with shielded control wire due to proximity to power wire) to the end of a three phase extension cord. Carry the cord end to the station and plug in.

Another option is contactors/relays can distribute power and control wiring to different machines if you have some cheap ones available. Push a button to select one machine, then power and control are routed to that station.
Using circuit breaker panels, you may be able to use mutually exclusive circuit breakers. Like you might use to select between mains power or a generator but not both. Easy to do with two, basically a slide between two breakers on opposite sides of a panel that will not let both engage simultaneously. Selector switches are another way to ensure mutual exclusion. You want something that is low in cost compared to the VFD itself, otherwise you might as well use multiple VFDs.

If you can use the same parameters, one centrally wired VFD with no remote speed control is in a sense no worse than a rotary phase converter. At worst, you set it for 60hz and leave it but you can change it if you really need to. But do not disconnect machines while the VFD is running as that is potentially bad for the drive/motor (spikes). Have at least gang wired VFD start/stop buttons. Be careful you don't have any machines that start up unexpectedly when you turn on the VFD because you left them on.

You can have each motor/machine plug into an outlet on a rotary phase convertor to run fixed frequency yet be able to unplug a machine and plug it into a VFD to vary speed.

You can physically lay out the machines to facilitate sharing one or more VFDs. One VFD could run the "background" machines: surface grinder or horizontal bandsaw. Another run the lathe or mill. Other machines connect to one or the other as convenient. With two machines sharing a VFD, it can be located between them, in some cases maybe even close enough you don't need to run extra stop/start buttons.

Carld
12-31-2009, 11:37 PM
I don't think it's that easy. It seems to me someone said the VFD's adjust to the motor they are running and that changing them from motor to motor causes problems. I think they have to be dedicated to one motor.

J Tiers
12-31-2009, 11:48 PM
A vector VFD DOES adapt to one motor, but a regular old-style V/Hz VFD will not care what it runs.

Even the vector VFD will re-adapt to any motor within its range with a start-up delay, so that alone isn't a big deal.

The biggest problem is having to have some way to conveniently control one VFD from a useful position that covers all your machines.... or figuring out a scheme to roll around the VFD to the machine, etc, etc.

Having an RPC is not bad... most all the 3 phase machines will have enough speed settings that they are perfectly useful with regular 3 phase, so the RPC is fine. VFD is really 'gravy", and shouldn't be considered an absolute necessity (unless you are really used to having it).

v860rich
01-01-2010, 02:28 AM
Here's how I did my RPC setup. I have a turn of the century American lathe that was run by a line shaft, and converted to an elect motor drive, 5 hp 3 phase. In order to get speed changes there is a 3 speed transmission with neutral.
I had a static converter on this lathe for about 10 yrs. when I added a second Bridgeport and a SB 16" lathe all I did was add a elect. junction box to the American, to wire the other machs into, start the 3ph motor with the static converter. I have the trans in neutral, now I have a RPC. I can run either mill or either lathe off this setup and I think run them all at the same time. Not likely I'd do that as I'm the only one here using the machines.
THANX RICH

People say I'm getting crankier as I get older. That's not it. I just find I enjoy annoying people a lot more now. Especially younger people!!!

kmccubbin
01-01-2010, 11:07 AM
I remember reading something a few years back that said it was a bad idea to power a VFD from an RPC, due to voltage spikes. Do I understand that some of y'all are doing this? Any problems?

Thanks,
Kerry

Orrin
01-01-2010, 12:44 PM
If I were in your shoes I'd make a RPC out of that three-phase motor you have. I have both, an RPC and VFD in my shop and prefer the RPC.

I have the VFD on a lathe and am all the time using the variable speed selection; but, it produces horrendous radio frequency interference that makes AM radio reception impossible within a 100-yard radius.

Except for some extra safety features, my RPC is a carbon copy of Carld's. I built the whole works from odds and ends I had around the place, except for a 50 Ampere plug that cost $25.

If you build an RPC you may want to put it in a doghouse, outdoors. I could never understand why my friends did that; after all, an idling electric motor doesn't make all that much noise. But, I'm now finding out for myself. I could do without that low background hum, especially while trying to listen to the radio.

Orrin

lakeside53
01-01-2010, 01:23 PM
You can solve the RFI issues with the correct filters. There are both line filters (for noise going back though the mains) and output filters (for the wires going the motor). Line filters do not have to be from the VFD manfs - there are many surplus filters available for very low $.

I don't have any "noticeable" Radio or TV issues with interference from any of my VFD (Hitachi and Teco). They are housed in metal boxes, have metallic conduit to the control boxes, shielded wire etc so some of the interference issues have been minimized by implementation.

mark61
01-01-2010, 01:33 PM
Everyone jumps on rotary converters and vfds. Does anyone ever take the time to see what having your electrical service upgraded to 3 phase would cost? If you can be a machinist there seems to me little about prepairing and installing the service drop then having it inspected that you couldn't do. Never have to mess around or worry about adding other machinery. You get to buy stuff cheaper because most everyone who doesn't have 3 phase won't be interested.The 3 phase would be a plus if you ever decide to sell the property unless you live in a development......
I installed the 3 phase in my shop. Since most of my equipment is single phase the cost for electric hardly ever goes to the high side of rate. They charge me per leg. Cost me $5k but that included a charge for the electric company to run new wires 200 yards down the road I live on and hang a new transformer. If my building was next to their main run they said not much more than meter installation charge.

mark61

lakeside53
01-01-2010, 02:02 PM
Where I live it's almost impossible (they have made exceptions..) to get three phase installed in a residential area unless you have a physically separate building from the house. One of mine is, and I checked... Our wiring is all underground and the upfront cost was about $20K - and I didn't even get to the part about minimum monthly charges...


I've seen some every nice 40KVA diesel generator sets going cheap lately...

wierdscience
01-01-2010, 02:27 PM
A little pricey,but the Cadillac of converters-

http://www.phaseperfect.com/products.htm

Tony
01-01-2010, 02:53 PM
[QUOTE=Carld]You have found a gold mine there. Your right in that since your a one man shop you only need an RPC and even if you run 2 or 3 machines the 5 hp RPC will run them.

This is the wiring diagram for my RPC and I have been using it for over 15 years. The VFD's are only needed if you want to vary the rpm of the motor and can only be used on one machine at a time as you well know.



Carl,
I don't see any capacitors in that diagram -- is that correct?

Also, don't know if you might have some insight on this, but my line
voltage is 220V already. Ie I don't have two 120 lines + Neutral. I just
have 1 220V line and 1 Neutral -- how might I accommodate for this this
in your schematic?

-Tony

Bill in Ky
01-01-2010, 03:09 PM
The 3rd leg (T3) is generated by the motor. T1 and T2 are the 220v hot wires coming from the panel.
A 3 phase motor will run on single phase 220v and generate the 3rd leg, it just won't start on 220. So the 110v motor is needed to spin up the generator motor.

bborr01
01-01-2010, 03:15 PM
Darn cats anyway. Don't ask.

jacampb2
01-01-2010, 03:18 PM
I remember reading something a few years back that said it was a bad idea to power a VFD from an RPC, due to voltage spikes. Do I understand that some of y'all are doing this? Any problems?

Thanks,
Kerry

I have a home made rotary converter--->220/480 entrance transformer which runs my little mill and 15x60 lathe. I run the spindle motor for the CNC via a 480 3 phase allen bradley VFD from the rotary/transformer output. I have 0 issues with the drive running off the rotary converter. The only issue I can think of is if your rotary converter is so poorly balanced that the VFD sees a huge phase mismatch. Some VFD's will fault on a dropped leg if they see one leg go way under or over threshold. You can easily balance the legs of your converter by fine tuning the capacitance. IIRC, I got all of mine within 5vAc of each other and that was good enough for my situation.

With out capacitors, you can easily see a very unbalanced output. Before I had mine tuned, I saw some readings as far as 40vAc apart. I can't imagine how poorly balanced they would be without the caps.

Later,
Jason

Carld
01-01-2010, 03:30 PM
I don't have balance caps but it would help to even the load on the legs if your running the machines hard. I have considered putting balance caps on. The caps move some current to the false or generated leg to power it and even the load as I understand it.

bborr01
01-01-2010, 04:04 PM
Darn cats anyway.

Jim Shaper
01-01-2010, 04:19 PM
I can see the 3ph wires from my driveway - it's about 1000' run.

For the PowCo to run those lines to me, I'd need:

3ph main step-down transformer (somewhere close to 10K I'm told).

All the wiring run (probably 4-6K bill from the PowCo)

New service entrance, meter, etc. (not too bad, but still not cheap - I'd guess close to 1000 in parts - with the service drop wires being about 500 of that)

From there, I'd end up with a monthly minimum usage charge in the neighborhood of $100 (my shop's power consumption is typically under $100/mo)

Which means that for a 15-20 grand investment I save absolutely NOTHING.

This assumes they'll even run the lines for you. I did ask at my parents house (another case where the 3ph mains were within eye shot) and they simply laughed followed by a "you're not in a service area for that power distribution."

Single phase from already existing 3ph is far easier to do. You just need a transformer in some cases and those can be had surplus for a few hundred bucks. If you have single and need 3, you need entirely new wiring and components for your service connection. An additional wire might not seem bad (3 hot's plus one ground), but it means all the junctions now need provisions for those three wires rather than the one or 2 from single phase.

jacampb2
01-01-2010, 04:31 PM
??????????????

I'm thinking you did that to yourself friend. Well, either that or a moderator is picking on you :)

Click reply and look directly above the "submit" and "preview" buttons, those are the post icons, and we can only add them to our own posts, not others.

You can probably edit your original post and switch it to "no icon".

Later,
Jason

bborr01
01-01-2010, 05:33 PM
Thanks Jason,
I think I had a little help from a cat.;)
Brian

Doc Nickel
01-01-2010, 06:24 PM
Native 3-phase to my place would run $10-$20,000, and $100-$200/mo over and above what it already costs.

Plus, there's supposedly a usage requirement of some form- don't use enough electricity? You pay an extra fee.

Third, the 3-phase service is essentially a perpetual cost. Supposedly if I ever got tired of paying the extra, or decided to retire and didn't need the service any more, or decided to sell and move to Florida, I would still have to pay the service fee. Such fee would have to be disclosed to a potential buyer, and they would have to contractually agree to pay for the service.

Now, I don't know the reasoning behind all that, and I have to admit that some of it's third hand so I may well have it wrong, but the bottom line is, it'd cost a minimum of $10K and an extra $100 a month.

I can buy a lot of VFDs for $11,200. :D And since I don't have, nor do I plan to get, any machines that have greater power requirements than a relatively inexpensive VFD can suck out of a residential single-phase line, installing native service doesn't make a whole lot of sense.

Doc.

clutch
01-01-2010, 07:04 PM
I'd go with a rpc. My mini shop only has a 3hp Clausing and a 1.5hp Bridgeport. Not much chance of me running both though. I've done that at work but only on some long turns while boring with the Bridgeport that will kick out the quill feed. That takes too much concentration, I make chips for relaxation at home.

I'm kicking myself for not adding a remote start to my current system. I have a 5hp RotoPhase my uncle found in a dumpster at an drilling location. Working 30 feet away inside an insulated room that thing winding away is annoying.

I left it idling for 18 hours recently, I think it cost me near a dollar to a dollar fifty based on daily readings from my utility. Kind of hard to extract that from running the electric heat in the shop and being home during the week.

Clutch

j king
01-01-2010, 07:22 PM
The 3rd leg (T3) is generated by the motor. T1 and T2 are the 220v hot wires coming from the panel.
A 3 phase motor will run on single phase 220v and generate the 3rd leg, it just won't start on 220. So the 110v motor is needed to spin up the generator motor.


I built a RPC with a 15 hp motor.It self starts on 220 single. The key I think is to have HUGE caps! I have a bank out of an electric furnace.I have an extra cap wired in on an extra contactor. I simply wired a push button switch to pull in the contactor that adds another cap to start.As soon as its up to speed I let off the button and am in business.

jacampb2
01-02-2010, 07:47 AM
I built a RPC with a 15 hp motor.It self starts on 220 single. The key I think is to have HUGE caps! I have a bank out of an electric furnace.I have an extra cap wired in on an extra contactor. I simply wired a push button switch to pull in the contactor that adds another cap to start.As soon as its up to speed I let off the button and am in business.

My RPC is self starting too. Rip cord start and pony motor start are IMHO the worst way to do it, although they are the least expensive way to do it.

Out on a limb, but my guess is that the people that complain about RPC whine and noise have either very poorly balanced converters or rip cord type with no caps at all. I start mine up, and can't hear it running after the initial start. While the start cap is in circuit, there is a pretty good high freq whine, but it gone when the start cap drops out. After that, it just sounds like a electric motor idling. I can hear the radio and anything else in the shop just fine.

Later,
Jason

Mcgyver
01-02-2010, 10:02 AM
I really like my phase converter. Built it myself, new bearings in the motor so its not too noisy and no rope start stuff. hit the switch on the panel, start caps kick in for 2 secs and then run caps carry things. based on a true RMS meter, all three legs show the same voltage and its performed perfectly (this balance is achieved by increasing/decreasing number of run caps). I will one day add a low voltage relay so i can turn it on and off from different points around the shop.

However, my sourcing made it the best (economical) solution. I got everything used and surplus. Did it all including motor a big electrical box for $400. if you were buying timers, starts, caps, large cases new etc you could easily go over a grand....

So as an alternative, if you can't source this stuff cheaply, what about a motor generator style phase converter? Basically you mechanically couple a big 240V motor to a 3 phase motor and generate the three phase. that's kind of the extent of my knowledge on it....if its just a matter of obtaining a big(ish) single phase motor it might be cheaper and less fuss...plus I've been told its better power so far as balance, spikes etc are concerned.

anyway, i don't know enough it to instruct, but wanted to point out the other style of rotary phase converter

http://www.electricpowergenerator.com/motor-generator-sets.html

J Tiers
01-02-2010, 11:34 AM
So as an alternative, if you can't source this stuff cheaply, what about a motor generator style phase converter? Basically you mechanically couple a big 240V motor to a 3 phase motor and generate the three phase. that's kind of the extent of my knowledge on it....if its just a matter of obtaining a big(ish) single phase motor it might be cheaper and less fuss...plus I've been told its better power so far as balance, spikes etc are concerned.


probably will NOT work, as the 3 phase motor cannot generate enough surge current to start motors unless they are very much smaller. The stand-alone induction generator is a fussy beast.

But if you could locate a 3 phase generator you'd be in clover. Unfortunately, most available ones that would be cheap or free are already melted down after the scrappies got them.

Carld
01-02-2010, 01:10 PM
I have a 3 ph 13.5 KW Onan propane generator that I have many times considered putting in a separate service to power my lathe and mill with. The trouble is it's not worth the effort and problems and the RPC is so easy to use it's not going to happen.

If I were running a two or three man shop full time I would consider using the generator because of the cost and issues of getting a 3 ph service run in.

Jim Shaper
01-02-2010, 02:40 PM
My RPC is self starting too. Rip cord start and pony motor start are IMHO the worst way to do it, although they are the least expensive way to do it.

Out on a limb, but my guess is that the people that complain about RPC whine and noise have either very poorly balanced converters or rip cord type with no caps at all. I start mine up, and can't hear it running after the initial start. While the start cap is in circuit, there is a pretty good high freq whine, but it gone when the start cap drops out. After that, it just sounds like a electric motor idling. I can hear the radio and anything else in the shop just fine.

Later,
Jason

Mine was a 10hp motor, and JUST the motor whirring was annoying. No noise from imbalance chatter.

Call me odd, but I like the noises I hear to be directly related to the machines I have running.

I'll take this a step further - 3M has a full time guy who goes around and listens to machinery to check it's condition. They have a program that analyzes the sound signature and checks it against previous records to verify the operating condition of the machines.

My music is loud enough to hear it, but quieter than the machine I'm working on. I can also still clearly hear the 4x6 bandsaw in the corner from the other end of the room.

I use multiple speakers placed around the shop to enable this.

Jim Shaper
01-02-2010, 02:50 PM
probably will NOT work, as the 3 phase motor cannot generate enough surge current to start motors unless they are very much smaller. The stand-alone induction generator is a fussy beast.

But if you could locate a 3 phase generator you'd be in clover. Unfortunately, most available ones that would be cheap or free are already melted down after the scrappies got them.

My 18KW gen head was $800 but only because it had extremely low use (should've been cheaper). This is good for 24hp.

You can find complete 3ph gensets on fleabay for 3-700 bucks if you don't need one so big and are willing to wait for the right deal to show up.

You can even buy new ones for that price range in the smaller sizes, but they're chinese and you'll likely need to rebuild the regulators.

bpsbtoolman
01-03-2010, 01:38 PM
I have been using a home built three phase generator for years , a 5 HP 3 phase motor started with a 110 volt half horse cap pony motor. Recently I decided I wanted a remote relay system to start and run it. So I belted up the 110 volt motor with one to one pulleys and start with a NO button, hold for about 10 seconds, then release while switching the on the driven generator. The 110 volt unpowered motor is driven by the generator. No problems yet. The pony motors are cheap and easily available if needed.
Walt

MichaelP
01-03-2010, 07:12 PM
My 18KW gen head was $800 but only because it had extremely low use (should've been cheaper). This is good for 24hp.
You can find complete 3ph gensets on fleabay for 3-700 bucks I wonder what the efficiency of the generator setup vs. RPC will be. I understand that the quality of the 3-phase current will be higher, but how about the overall efficiency?

lakeside53
01-03-2010, 08:05 PM
Best case 80% (drive motor) of 80% (generator)? Hard to say.. depends on how hard you use it. Motor efficiency is typically rated at full output, and they are lousy at low output.

Jim Shaper
01-03-2010, 10:56 PM
The generator I have is a very efficient design, but only by generator standards. :D

Belt drive loss is probably more of an issue than anything.

I've got a vfd with 98% efficiency driving a high efficiency baldor motor that's 40% over needed output (no effort on motor plus added inertia benefit - flywheel effect for surges) driving a genset which is rated for absolute peak load of a machine that likely will never see it.

It can't be any worse than my RPC was. At least this time around the reactive load is isolated from the mains and disbursed into the caps of the vfd power supply rather than shoved through the mains to spin my digital power meter.

If I was still on an old analog meter, I'd probably have never switched to vfds. The reactive current would spin that meter backwards, where as the digital one charged me in full and then some.

Right now my only useful data on the matter is the idle load of driving the generator is 15A on 230v (this is while connected via a rather long 6ga cord through a 50A circuit). Once I get a power supply on the turning center fixed and the proper 4ga wires run with a 100A circuit, I'll be able to do more meaningful measurements.

MichaelP
01-04-2010, 12:36 PM
Thanks, guys.

Jim, what's the approx. size/weight of your generator setup? Do you happen to have a photo?

What are the minuses of such setup vs. RPC? I just wonder why people would discuss RPC at all for the ranges of power you mentioned if there is such an affordable (relatively speaking) way to get a perfect 3-phase (vs. not quite balanced one after RPC).

lakeside53
01-04-2010, 12:53 PM
Maybe I missed something.. but isn't the only way to make it "affordable" is if you have a 3 phase generator lying around? I've seen plenty of 3 phase 35-50KVa generator heads as "scrap", but very few of the more desirable 10-15kva... Ebay is interesting, but freight can be a killer. I did just find one on Ebay... only one...and it's 10KVA for $700 (plus shipping). If it is really 10KVA out (at pf 1.0 and not just "peak"), I'd likely need to feed it with a 10-12hp single phase motor. Even then, I wonder if it could start a typical 7hp motor?

I run my 15 KVa single phase Motor generator often.. wish it was a three phase:(


Jim: Your high efficiency Baldor... IIRC... is still miserable efficiency unless at full load... which is where many motors unfortunately run unless driving a matched full load - like a fan. But I agree... it's good way to get decent three phase power. Lack of efficiency just means to need less money for shop heat - should all balance out in the winter :)

Jim Shaper
01-04-2010, 02:49 PM
My set up is simply the gen head (self supported - no need to be attached to the flywheel of an engine) side by side with the motor and then v-belted together with equal diameter sheeves.

What's been said about the smaller genset's being hard to find is also true about the smaller vfd's. A 50hp drive would've sufficed for my needs, but a 75hp was 4-700 cheaper. :eek: So I just went bigger. :D

Same with the 40hp baldor. I really only needed a 30hp motor, but my 40 was $350 and a 30 would've cost me close to a grand in far worse shape (my baldor had been used in a prototype where the housing didn't fit the available hole - it was Brand NEW). Bigger usually means cheaper in industrial used stuff.

I reprogrammed my vfd to think it's a 40hp, so it should control the motor effectively regardless of the power requirements of the genset. Rather than running off line current, the vfd does improve the energy consumption of the motor as it's an active drive. There's no need to allow full current to flow unless an appropriate load is applied. Again, the genset won't resist turning until a load is applied to it, so the two should balance out to a higher over all efficiency.


As for why more people don't do this? Because they probably think it's cost prohibitive. I have a cnc machine that was either going to need my method, or a phase perfect at over $4K. I chose to go the cheaper route.

lakeside53
01-04-2010, 05:52 PM
ha... I have 2 x 200 amp panels for my house/shop, and after diverting "some" power to life support (swmbo):D I still couldn't realistically run a 40 hp single phase drive at 40 hp... the soft start features help, but... a 160 -200 amp breaker.... Hmmm...maybe the the electric sauna could go... :cool:

Jim Shaper
01-04-2010, 09:02 PM
My vfd should peak out at around 100A, which happens to be pretty close to where my tig maxes as well.

I've got my electrical permit, so I should be having mr sparky inspector here tomorrow to find out what he thinks I should do about the max load on my 200A panel. I may end up installing another.