Another 3 phase power question

[Keith Avery]

I have a delta 33-411 16" RAS. I have never had power on it, I did a complete restoration in my barn but had no electricity out there at the time. The motor looks pristine and I doubt I will have issues with it working properly once elctric is done correctly. I have a 100 amp panel in the barn now. This will be for hobby purposes. Now that I have power in barn I need to make the final decision on how to power it. I have read the threads to death about this topic but find no concensus of best solutions.

1) The 3 phase 5 hp motor is rated and 12.8 amps I think. I have found some vfds rated around 10-12 amps for 300 ish dollars. Would this work? Stepping up to vfd rated at 13 plus amps doubles the price, at least last time I looked. I also find the wiring of this setup a little confusing but I am sure I can figure it out. EE was my least favorite subject in college.

2) Grizzly has a static phase converter that is supposed to be capable or providing up to 90 percent power for a couple of minutes. I doubt an RAS would ever pull max power for more than 30-40 seconds at a time. Opinions? I think this would cost 200-250.

3) Rotary phase converter. Thinking with additional panel and wiring and rpc I am looking at about 1k in cost but expandable. My most likely second 3 phase purchase would be a compressor and I understand this does not work well. I also wonder about the constant noise from the RPC. I am not interested in building from scratch. I don't have the time to tinker nor the skill or inclination. I hate all to do with electricity.

Looking for opinions on what you would do? Money isn't the main issue but I don't want the trouble of wiring rpc and panel etc if a plain old static converter will do the job fine. Currently I am leaning to a slightly underrated vfd. Most of the specs appear to be able to take 150 percent of rated amperage for up to a minute before shutdown and I really doubt even that big RAS will need a full 5hp very often.

[David Kumm]

Keith, If you like old machines you will continue down the three phase path. The long term solution is an RPC. Keep watching for used but buy a quality unit when you do. Kay industries, American rotary etc. Check out OWWM.org for discussions on brands. For now a vfd will get you running but keep in mind that most are listed as 3 phase in- three phase out. They can can be operated with single phase input but must be derated accordingly. Therefore you need a 230v 7.5 to 10hp to get you what you need. If you watch fleabay you can find a used one for 350 to 450. You also need to check the starter on your RAS. A magnetic won't work so you need to wire the vfd direct to the motor. If the saw has a manual starter you can leave it in place, turn it on and plug the cord into the vfd. Use the vfd as on off but leave the manual switch as emergency stop. Don't be discouraged as three phase opens up so many opportunities it is worth the effort. My disk sander, vertical mill, borer. dust collector, and mortiser are all powered by vfd for the speed control. Now I consider a machine with a single phase motor a negative rather than positive. I would not go the static route. Save your money for the real deal. The wiring is not that hard, I have done all my own over the years. Try the vfd and go from there. Dave

[Carroll Courtney]

http://www.factorymation.com/ This who I purchase mine from and its single phase in/three phase out.Your right,there's a jump in price going from 1hp up to 3hp.The drive that your looking at that's just alittle under in amp rating will work.Just remember to run the hz up to where it will not over amp the smaller drive.Which you can set the upper limit of the drive to that point.VFD's will not work on an air compressor due to the startup loads ince the tank has air in it.The motor for the air compressor has to reach max rpms very quick for it not to over amp and trip on OL's.Having to run a rotary phase or static phase all the time for a compressor when it needs to come on,well not to much to gain there.Post some pics of your progress w/which ever way you go---Carroll

[Tom Cornish]

VFDs are great for single motor machines. There is one big gotcha on most VFDs though - you must not use a switch between the VFD and motor, or you will blow up the VFD. If you want to use the original switch on the tool, you must re-wire that to the VFD contact closure inputs, and then directly wire the motor to the VFD output. You can't just stick an outlet on the VFD and plug the machine in. VFDs also can't be used on more complicated machines that have more than one motor for the same reason - for those a rotary converter is your choice.

+1 on the FactoryMation ones - I have a Teco 3HP 1 phase in 3 phase out on my Bridgeport and it works really well.

[Tom Cornish]

VFD's will not work on an air compressor due to the constant load.
How do you figure? VFDs are used all the time in continuous duty applications such as HVAC fan speed controls. I wouldn't have any problem with running an appropriately sized VFD for an air compressor, so long as the pressure switch was wired as a control input to the VFD and the VFD controlled the cycling.

[Tom Cornish]

. They can can be operated with single phase input but must be derated accordingly. Therefore you need a 230v 7.5 to 10hp to get you what you need. If you watch fleabay you can find a used one for 350 to 450. This may be possible depending on the particular unit in question, but comes with some risk. I just looked and FactoryMation doesn't seem to have a 5HP 1 phase in 3 phase out model, but here's one from another source:
http://www.driveswarehouse.com/Drives/AC+Drives/Phase+Converter+VFD/PC1-50.html?osCsid=b527606cf949207e69ba3c752bcb6967

[Ryan Hellmer]

Rotary phase converters can be built relatively simply. A quick google search will yeild lots of suggestions. I built my own by purchasing a control panel with start capacitors and run capacitors to help balance the legs. At least several folks I know have built there own using a single phase (say 1/2 HP) pony motor to bring the 3 phase motor up to speed, then apply power to the "idler" motor and bam, there's three phase.

My RPC is push button start and located on a rolling cart with about 20 feet of cord (to plug into my 220v single phase receptacle). This obviously requires that I only plug in one machine at a time. The noise from my RPC is neglegible, I usually start it, perform whatever operations are required and then shut it down. No sense having it running full time if I'm going to use it. Keep in mind this is in a one man hobby shop.

As David pointed out, if you even intend on more than one machine, an RPC makes sense. I bought a VFD for about $200 for my first three phase machine thinking it was all I needed. Then I got a three phase drill press, well I could just re-program... Long story short, I now have 7 three phase machines which, with an RPC, has my per-machine conversion cost pretty low. Don't be penny wise and pound foolish.

Ryan

[David Kumm]

I am running about 6 or 8 different brands of used vfd's and none of them are listed as single phase in but all work that way. Most of them address that in the instructions. My Hitachi j300 is the only exeption and all I had to do there was jump two of the input terminals. As to blowing up a vfd with a switch I understand not taking chances but again all my vfds are wired with plugs as I sometimes use the machines right off the RPC. If you leave a manual switch in the on position the vfd will not know the difference. I have had occasion to hit the switch in an emergency. One of my vfd's hits an error code and I need to reset, all others don't know the difference and think the motor is still on. I am not recommending that but I prefer to take a chance on the vfd rather than on me. Again, it is only that I am preserving the ability to run my machines either way that I go that route. Most factory support people are pretty good to deal with, even if your vfd is used. They will tell you if you can use a 3 phase input with single phase if you call and ask- before you buy. Dave

[Tom Cornish]

If you leave a manual switch in the on position the vfd will not know the difference. I have had occasion to hit the switch in an emergency. Why not just re-wire the switch into the VFD as a control input? There is no downside that I can see - machine operates as designed, and arguably it's safer than using the tool's switch inline with the motor, since the VFD can do electric braking which will slow the tool down faster than just freewheeling which would happen with your method.

[Alan Schaffter]

Why not just re-wire the switch into the VFD as a control input? There is no downside that I can see - machine operates as designed, and arguably it's safer than using the tool's switch inline with the motor, since the VFD can do electric braking which will slow the tool down faster than just freewheeling which would happen with your method.

I kept the original switch on my DP, but it only powers the VFD. The small toggle switch below the speed pot starts and stops the motor via a low voltage circuit to the VFD. Some VFD's can be set to start the motor (usually with a delay) on power up without the additional switch, but then you may or may not get the breaking. (the tach is a totally separate component)

The problem with a VFD on a compressor is the pressure switch. You'd need to leave the VFD on all the time and control the motor via the VFD with the pressure switch.

http://www.ncwoodworker.net/pp/data/500/DP-7.JPG

[David Kumm]

Tom, I hear what you are saying and agree. However, I like to be able to run stuff on the RPC when it is going. Has to do with the amounts of available amps in my shop. I run the RPC when I need to and then plug stuff into the system bypassing the vfd. When I don't need the big RPC I plug stuff into the vfd and use it. Still get electronic braking etc. My converter has voltage spikes in the manufactured leg until motors start running so it isn't practical to use the vfd with 3 phase input as the leg gets fried. I still use the vfd as on-off- the manual is only for emergency and also provides additional overload protection. I don't need to reprogram the vfd for overload if I move it because the switch has me covered. I should but you know how it goes when you only need something for a minute. Dave

[Don Buck]

For my 2 cents worth - I acquired a similar BS - a Delta 20" 3 phase out of a closed high school shop. I went with an American Rotary 5 hp rotary converter, purchased a used 3 phase distribution box and used disconnect from a company I discovered on eBay (less than $125 for both) and had it up and running for less than $800. I've since purchased a nice 3 phase radial arm saw that is running off the same converter. Only a one man shop but I could run both as long as they started in succession. As far as noise, the sound from the converter is just a low level hum. I've no connections with American Rotary but they were great in getting me on the right tract for the right sized converter and helped me trouble shoot my saw when it went down a few months later. With their help I was able to determine that the converter was working fine and was isolate the problem to a loose wire in the switch of the saw.

[Tom Cornish]

Here's my Bridgeport with TECO VFD

192157

I used the Bridgeport to cut a square hole in an aluminum project box for the remote control panel for the VFD, and rewired the switch to operate the on/off and direction controls of the motor. I use the "real" Bridgeport switch to turn the machine on and off, and occasionally use the VFD to adjust motor speed, but since my Bridgeport is already variable speed, I generally adjust the Reeves drive.

192158
The VFD, braking resistor, disconnect switch, circuit breaker, and convenience outlets for the readout and future power feeds are in the enclosure. The total cost was about $500. I could have done it cheaper, but wanted to do a nice job.

For a Bridgeport or lathe, or any machine where variable speed is desirable, it's hard to beat a VFD. For saws, shapers, and other things where variable speed isn't a plus, for non-single-motor machines, or a shop with a bunch of 3-phase machines, a rotary converter with 3-phase distribution is the better route.

[Chip Lindley]

I'm with Ryan. I vote for an RPC! I have successfully used an ARCO Model A, 5hp unit, and now a Model R, 7.5hp unit for over 20 years. It is wired up to a magnetic starter with remote capability. I push the button on my keychain remote to turn it on and off, right at the machine I am using.

There are many bargains on used RPCs out there now as users replace RPCs with solid-state solutions. Just beware that some suspect "5hp" units will not start a 5hp motor. Read the fine print. Reputable, commercial brands are rated to start a certain Hp. motor, and will run up to two other motors of the same Hp. when started separately.

Once installed, a decent RPC will run ANY machine up to the rated horsepower of your unit. Unlike VFDs which must be wired separately each time you install one, wire up your RPC once and you are Done! Go for a 7.5hp or 10hp-rated unit now and you will never have to trade up again--UNLESS you luck into a heavy bargain on a wide belt sander.

[Tom Cornish]

I kept the original switch on my DP, but it only powers the VFD. The small toggle switch below the speed pot starts and stops the motor via a low voltage circuit to the VFD. Some VFD's can be set to start the motor (usually with a delay) on power up without the additional switch, but then you may or may not get the breaking. (the tach is a totally separate component)

The problem with a VFD on a compressor is the pressure switch. You'd need to leave the VFD on all the time and control the motor via the VFD with the pressure switch.

http://www.ncwoodworker.net/pp/data/500/DP-7.JPG

That's a really nice integration into the machine.

[Carroll Courtney]

Tom your right I change my wording, editing my post.Tom your correct about the drives for HVAC industry,thats what I do for a living.VFD's run AHU's,pumps,cooling tower motors,etc.Its the start up amps that a compressor needs to get it going with air in the tank,even if the air compressor has an unloader.The startup amps for AHU's etc is small using VFD's cause there is no load,even pumps that cir.water starts up w/no load.
I figure that if there was a benefit or possible using a drive for air compressors,I would have seen it by now since alot of the schools still use air compressors for the controls.All of my post(this subject or others) is just my opinion and I don't claim to know it all---Carroll

[Tom Cornish]

I think that a lot of the reason you don't see VFDs on air compressors in commercial settings is that there isn't really any benefit to slowing them down. HVAC motors and pumps can often be run at less than 60Hz, saving energy. Air compressors run until charged, then shut off - generally speaking it's desirable to have this happen as quickly as possible. Once charged, the compressor draws no power at all until needed again, so it's a pretty efficient system.

I still don't see any reason that a properly sized VFD couldn't start a compressor - you might have to oversize the VFD so that the starting current doesn't overload the VFD, but VFDs are made all the way from small fractions of a HP to multi-thousand HP diesel electric locomotive sizes.

[Brian Brightwell]

I agree with Chip. I built my RPC from scratch for not much money. My first 3 phase tool was a 10HP wide belt sander. Then I added a 5HP radial arm saw. Last week I bought a "drawer sander" and a 1Hp pump sander, all 3 phase. The drawer sander has 15inch by 15foot belt is powered by two 5hp motors and weights 1600lbs. The asking price was $1395 I got it for $350. I got it started today and runs great. I didn't even have to track the belt.
I think single phase is the way to go for air compressor and dust collection which leaves the RPC for the good old iron which you only run one at a time anyway.

[Rick Lizek]

This may be possible depending on the particular unit in question, but comes with some risk. I just looked and FactoryMation doesn't seem to have a 5HP 1 phase in 3 phase out model, but here's one from another source:
http://www.driveswarehouse.com/Drives/AC+Drives/Phase+Converter+VFD/PC1-50.html?osCsid=b527606cf949207e69ba3c752bcb6967

Dave is correct about "Derating"!!! I've had this conversation with techs at factorymation about this topic many times. Too many folks just jump on a site and expect to find all the answers in two seconds. They do have the appropriate VFD but haven't derated them all for the novice. I see more bad electrical info than good on forums.

[Tom Cornish]

This may be possible depending on the particular unit in question, but comes with some risk. I just looked and FactoryMation doesn't seem to have a 5HP 1 phase in 3 phase out model, but here's one from another source:
http://www.driveswarehouse.com/Drive...ba3c752bcb6967 (http://www.driveswarehouse.com/Drives/AC+Drives/Phase+Converter+VFD/PC1-50.html?osCsid=b527606cf949207e69ba3c752bcb6967)



Dave is correct about "Derating"!!! I've had this conversation with techs at factorymation about this topic many times. Too many folks just jump on a site and expect to find all the answers in two seconds. They do have the appropriate VFD but haven't derated them all for the novice. I see more bad electrical info than good on forums.Oh? You know for certain that it is axiomatic that every VFD built buy every manufacturer can work with the same de-rating schedule, is free of internal fault detection mechanisms that may alarm when one leg is un-fed or if the phase delta between legs is 180 degrees instead of 120, and that the manufacturer's warranty will be unaffected if you use a device in a manner they haven't specified? That there are absolutely no other consequences in any circumstance with any VFD on the planet?

I find it a little strange that you pick my post as your example of all that's wrong with electrical advice on the internet when in essence I'm recommending that the OP use a device specified by the manufacturer for the purpose in question., i.e single-phase in and 3-phase out. Did I pick up the phone and call FactoryMation in this particular case to see if any of their units have unadvertized capabilities? No - you got me there. Did I find a different suitable unit? Yes, in about two seconds.