Advice on converting bandsaw 3phase-1 phase

[PurdueSD]

Hey guys... Supposed I was to happen upon one of these:

http://www.doallsawing.com/band_saws_details.aspx?mod_sku=CMI290166&cat_id=6#

How would you go about converting it to run on 1 phase power...

The motor in the one i am speaking of is q 470V 3 phase 60Hz 2HP baldor. It says its 1425 RPM which i have never heard of. My thinking is- purchasing a new 2 HP 240V motor and swapping it out would be much easier than a phase converter. The only thing that scared me is the motor controls... It has a small cabinet with start/ stop switches and what look to be a couple relays... Did i mention i hate control wiring. I do have some friends to call though...


Let me know what you think...and yeah i know- i ****!

 

[LoneGunman]

Swapping in a single phase motor is the way to go, it's going to be cheaper than a phase convertor. I bought my 7.5 HP Baldor on Ebay from the link below, great sellers and the best price I could find on quality motors, Nissan Crawler got a motor from these guys also.

http://stores.ebay.com/WECO-GROUP

 

[John Timmins]

Without a whole lot of electrical theory...not using the phase converter is the way to go. It will not make 3 phase power that is the same as what would come down your power pole if it is even available on your street.

A phase converter will ultimately make your machinery useable but at a cost that is less efficient and less that perfect electricity being available to run the machniery. I would change the motor. Some shops have used and repaired motors.

The control box and relays is simply put a bigger on-off switch being operated by smaller on-off push buttons. The relays are no big deal once they are installed.

A way to describe what's happening is to use your car as an example. To start your car you turn the key which completes a circuit. It closes the starter relay (big switch) that connects the big fat wires from your battery to the starter.

If this is still confusing I can write more but I'm trying to make a real short simple answer.

 

[PurdueSD]

^Thanks for the advice guys!

Here she is...

Here is the control wiring... (anyone care to make sense of it for me) I assume the mini transformer was meant to convert the 480 to 120 for the light. Will i need to change any of the relay wiring when converting to 220V single phase? I assume the transformer will need to be replaced unless i dont use the light.

 

[Uncle Buck]

I think you should answer a few other questions before simply swapping motors.

1) Is there any chance you might add used 3ph equipment such as a metal lathe, a milling machine etc. Most of which have 3ph in the future?

2) If so do you want to buy a new motor at great expense for each piece of equipment every time?

3) You should PM OldCarGuy, I think he will tell you that all of that equipment in his shop has been phase converted.

4) You might also ask this same question on the Practical Machinist Message Board. I think you will find most home shops that have larger equipment such as your saw generally opt for phase converting instead of motor swapping.

5) Once you get a phase converter of sufficient size you are set for any future purchases of 3ph equipment you add in the future whereas if you choose to swap motors there will be extensive additional costs each time you add a new machine.

 

[nissan_crawler]

He's right, it depends on future plans. If this is realistically the only 3 phase piece of equipment you'll own, just chuck a new motor on it. You can get that rpm easily. i have a 5hp of that rpm, cost me $280 I think.

If you're going to have 2-3 3 phase items...then a converter starts looking attractive.

 

[Uncle Buck]

He's right, it depends on future plans. If this is realistically the only 3 phase piece of equipment you'll own, just chuck a new motor on it. You can get that rpm easily. i have a 5hp of that rpm, cost me $280 I think.

If you're going to have 2-3 3 phase items...then a converter starts looking attractive.

Damn, I knew there was a faster way of gettin that said.........Damn I am windy!

 

[PurdueSD]

Thanks guys... this is the only piece of the 3 phase equipment i plan to have... at least for quite a while. So swapping the motor out wins... now about the wiring...?

 

[swgray]

If the overload on the contactor is a piggyback style(I believe it is) you'd need to get one that matches the amp rating of your new motor. Also eliminate one leg of wiring (L3, T3) from the On/Off switch all the way to the motor.

Also change the wire on the input side of the multi tap transformer to whatever your voltage is or will be. 208v / 220v whichever it may be.

I see from the crank on the front, the variable speed must be using a variable sheave vs. a frequency drive.

 

[tigmusky]

before you swap that motor. make sure you get the right size! 3ph hp is not the same as 1ph hp. I know hp is hp , but its not. I went throught the same thing on a drillpress a few years back. 3 ph has 3 poles no caps. 1ph motors will none ,1,or 2 caps. the caps are for load starting such as air comp. your going to need more then a 2hp 1 ph motor. If you put the 2 hp 1ph on and it start it prolebly won't cut . A staic phase conv. are cheap , like 150.00 and less. this way you mount box run your 220 1ph to it then hook it up to your saw and you 2/3 of the power. a rotory phase conv.are better because it more of a true 3 ph but alot more coin! to make your own 3ph rotory is pretty easy and cheap if you can find and 3 ph motor . i made mine for about 120.00 .
Just remember 3ph tools drillpress lathe mill are cheap, most homeowners don;t have 3ph and are scared of it. Be a pimp go 3 ph!!!

Sorry tobe a buzz kill!!!

Good luck daye

 

[tfi racing]

Check with a local motor rewind shop,they may take your motor as a trade towards the motor you need and should be able to give you the right replacement.Also check with the saw company,I'm sure they make that saw in a single phase voltage and can recommend an HP rating.You may need to change the coil in the contactor,the xformer supplies the control voltage as well as powers the light,it may have to be changed as well.That and a bit of rewiring will get you sawing away.

 

[PurdueSD]

Anybody interested in building me a rotary phase converter?

...this may end up costing about the same as a new motor and could be used for another piece of equipment down the road.

 

[dwilliams35]

rotary phase converters are easy. look on Practical Machinist: they've got several plans. I built mine off of one, and it works great. Meanwhile, you've got a lot of work ahead of you to convert that thing: if it was built for 460v as the picture indicated,, you're going to look at the very least converting, and at the most changing, the control transformer. You've also got to change the motor overload out for the "new" amperage, maybe even change the entire starter wiring to lose the third phase, depends on how things are set up for the control wiring. Then there's the possibility that the wiring can't handle the lower voltage (higher amperage). Sure, it can be done. It's not necessarily an easy one, though.

 

[tigmusky]

Anybody interested in building me a rotary phase converter?

...this may end up costing about the same as a new motor and could be used for another piece of equipment down the road.

sure . pm me and give you # of a guy to call in az. the box will cost about 120.00 you supply a 3 ph motor a little wireing and your good to go. the trick is to find a 3ph motor cheap! I'll try to post some pix of my set up later,I have a hell of a time posting pixs . daye

 

[PurdueSD]

Hey guys, Ive been following the milling machine thread and it has brought up some more questions. I don't technically own the machine...yet. It is borrowed from a friends buisness. The saw had been sitting in cold storage for the last 2-3 years. They have a duplicate in their shop that i have used several times. He said the only way he would need it back, is if something happened to the other one. Based off what i have read about doall equipment, i dont thik this will be a problem.

Anyways I want to get the saw usuable without changing out the motor or controls, in case i have to take it back. So some type of phase conversion is what i need.

I understand the basic concept of Rotary phase converters, but building one is a little over my head.

I read in the other thread about the VFD recomendation. I was unaware VFDs were capable of 1 phase in 3 phase out. I thought they were basically a potentieometer. The saw already has a pretty elaborate speed control, so the added feature of frequency adjustment really doesnt help me out.

Also a friend of a friend recomended an inverter. But i have heard mixed reviews on their use.

Anyone care to recomend one of the above methods over the other. I am trying to make this as cost effective as possible but dont want to burn anything up either.

Please let me know your thoughts.

 

[kvom]

A VFD is still the way to go IMO. It will probably cost you less than an RPC in the long run, and they are compact and easy to hook up. In addition you will be able to use it for any additional 3PH gear you might acquire in the future. I'd get a 3HP model to run the 2HP version, as you must derate them with 1PH input.

If you were to find a suitable 2HP+ 3PH motor cheaply then there's no reason that the RPC would not work as well. In that case however, swapping in that motor to the saw might be the cheapest option (you can save the original motor in case your friend needs it back).

If you go the VFD or RPC route you would want to change the motor wiring to run on 230V rather than 470.

 

[W-Cummins]

looks like you may have to change out a bit of the control stuff to run it under 240v single phase VS the 480V 3 phase. I can't tell for sure from your picture if the transformer is just running the light or if it's powering the contactor coil too. So anyway, the contactor may be too small to be used at 240v 3 phase (2Hp 3phase NEMA 00 @480V VS NEMA 0 @240V) and is most certainly too small for 240V single phase operation. If it has a 480V coil in it you sol with it anyway. So to move forward you need to know the NEMA rating on the contactor and it's coil voltage. The wire used will work ok for either use as it's probably 12 gauge to the motor anyway. So to start you will need to re-connect the motor leads on the motor ( assuming it's a dual voltage motor 230/460V)

Looks to me like it will be cheaper to power this with a VFD as you will bypass the contactor and overloads so they will not be used and you will not have to buy the correct sized ones. Also if you have to return it to its owner at a later time the re-conversion to 480V will be, just hook it back up and reconnect the motor legs.

William....

 

[Torque1st]

Get a phase converter and skip all the control wiring mess, VFD wiring changes, or motor change.

 

[W-Cummins]

Get a phase converter and skip all the control wiring mess,

Please tell me how getting a phase converter is going to allow you to skip this?? Or are you sugesting a phase converter and a 3 phase step up $$transformer$$ ??

William....

 

[PurdueSD]

Thanks for all the advice guys, i like the vfd (inverter) angle. Any ideas on where to purchase and what to look for.

So far I have heard i need a 3HP VFD 220V single phase input/ 240V 3 phase output.

Will i need to purchase anything else? Possibly a transformer? Would additional pitctures help?

 

[Torque1st]

Please tell me how getting a phase converter is going to allow you to skip this?? Or are you sugesting a phase converter and a 3 phase step up $$transformer$$ ??

William....

You don't know????

He has a 3-phase machine built to run on 3-Phase. He will need the appropriate step-up transformers for 460 service. Those transformers can be found at many surplus dealers. If he goes with a VFD or a single phase motor he will have to replace or rewire most of his controls.

People seem to forget that nice shiny cheap 3-phase tool they buy will need power.

 

[dwilliams35]

It's fairly rare to find a machine tool that can't be converted from 460 to 240 or back: Most of the exceptions are either CNC or have a VFD or soft-start already installed: you have to have the right input voltage for the VFD. Most of the ones I've run across are actually set up with wire sizes, etc. for 240 v or 208 v 3-phase power; those wire sizes are overkill when you convert it over to 460. It's generally fairly easy to change it, but I really wouldn't try it if I didn't have a pretty good background in electrical control. It'd be a heck of a lot cheaper than a step-up transformer, one way or another.
Most of the problem with adding a VFD is just with multiple motors: you can't get 3-phase for the whole machine with a single VFD: pump motors, traverse motors, stuff like that still need 3 phase. If it is a single motor, it's generally not that hard: you're only really worried about making sure you get the correct control power; the contactors, etc. will work just as well without a true third phase.

 

[PurdueSD]

Anybody care to weigh in on this?


http://www.grizzly.com/products/Static-Phase-Converter-2-to-5-HP/G5842

 

[dwilliams35]

Anybody care to weigh in on this?


http://www.grizzly.com/products/Static-Phase-Converter-2-to-5-HP/G5842

I'd say no way: Rotary converters are every bit worth the extra money: they come up with something resembling a third phase, at least: a static converter just gets the motor started and then runs on single phase power, with the motor only developing a portion of rated power. They are EASY to build: look on the Practical Machinist site mentioned here: I built mine with a freebie old motor, some used electrical gear I had been pack-ratting, and thirty-five bucks worth of capacitors from Grainger.

 

[Nealcrenshaw]

Man,This stuff is waaayy over my head,I better start reading some books!!

 

[hidollartoys]

Purdue, I will cautiously weigh in. I have been deeply researching this for about 3 months and maybe I can be some help. Static phase converters (spc) are ok if you can stand about a 30 to 40% derating in the horsepower of the motors that you are going to run. You will need multiple spc's if the saw has more than one motor, one for each motor.

As for rotory phase convertors (rpc), they are fine if you dont mind an additional motor running just to run another motor. You MUST start the rotory BEFORE starting the motor doing the work (saw). There are plans and advice about this all over the web, just google. There are several criteria for proper sizing of the pilot motor and tuning capacitors. Your primary power feed to the system depends on the total current of all motors in the system including the pilot motor. Unless you are going to use this saw for production you will be ok with a home built albeit sloppy rpc. Lots of them out there working. It will also be the best route for the money both long and short term. There are limitations to the rpc's relative to multiple motors and max motor hp. At 3 hp you will be ok, but if you want to run a hard start motor such as a compressor then you will need a very large rpc relative to the actual working motor. A single rpc can operate multiple motors within the constrants of the hp size of the rpc. This is probably the best solution for you. Build one dont buy one. Get someone to help you that knows something about electricity and electrical theory.

I would stay away from the VFD because they will be dedicated to the single motor. Multiple motors require multiple VFD's. Also VERY expensive. Same with inverters.

There is another method out there. It is the auto-transformer method. It is an old technology that has gone by the wayside for economic reasons. However a couple of guys have resurrected this method and it might provide a better alternative to the other methods. The only problem is it is not a " plug-and-play " issue. This idea will require a strong understanding of electrical theory and material resourcefulness. If you are interested : unique3phase.com. Doug is a good guy and has good testing to support this method. I am personally building a 20 kva (83 amps@240v)converter now.

 

[Aceman]

This is more trouble than it's worth IMO. Converting 240v single phase to 480 3 phase for a machine that's not even yours doesn't make sense to me.

If I owned it, it'd be getting a single phase motor and most likely a larger starter to handle the higher current. New motors are fairly cheap on Ebay as long as it isn't some weird frame size you can't find.

 

[hidollartoys]

I might add that changing the motor is always a viable alternative but a 2hp 3 phase motor is not ths same size as (smaller than) a 2hp single phase motor regardless of the frame. You will need to determine the frame type and then the physical size of the motor to see if you have room. Usually this is not a problem until you get to 5hp motors. There might also be a fitment issue with the motor shaft/sheave. Most times a conversion will require a larger hp single phase motor than the original 3 phase motor. There is a motor efficiency issue that you should address. Application is a factor in the proper motor choice. You should check with a local motor shop for the best alternative to the 3 phase motor.

 

[PurdueSD]

This is more trouble than it's worth IMO. Converting 240v single phase to 480 3 phase for a machine that's not even yours doesn't make sense to me.

If I owned it, it'd be getting a single phase motor and most likely a larger starter to handle the higher current. New motors are fairly cheap on Ebay as long as it isn't some weird frame size you can't find.

So putting $200 into a piece of equipment that is worth about 7K is stupid...? A harbor freight horizontal band saw cost about as much or more than getting this one up and running should.

- Which would you rather use....And Honestly, chances are I wont ever need to return it.

New motor has been and still is being considered, however its not just as simple as swapping in a motor. And I am not a motor controls guru. ANd building a RPC or buying an inverter are both cheaper options than buying a new motor.

 

[PurdueSD]

I might add that changing the motor is always a viable alternative but a 2hp 3 phase motor is not ths same size as (smaller than) a 2hp single phase motor regardless of the frame. You will need to determine the frame type and then the physical size of the motor to see if you have room. Usually this is not a problem until you get to 5hp motors. There might also be a fitment issue with the motor shaft/sheave. Most times a conversion will require a larger hp single phase motor than the original 3 phase motor. There is a motor efficiency issue that you should address. Application is a factor in the proper motor choice. You should check with a local motor shop for the best alternative to the 3 phase motor.

Good point, space is abundant where the motor resides, but the wiring intimidates me a little. Looks like the transformer converts the 480 to 120V for control wiring.

Thanks for all the advice guys!

 

[Dr. Bolt]

Old thread but here's my $.02
The VFD's are the way to go. Not only can they convert 220 single phase to 230 three phase but they can be programmed as a brake, reversible and to control speeds.

I have a TECO 7300CV on my 2hp Bridgeport and love it. I paid around $150.

 

[nadogail]

.... I don't technically own the machine...yet. It is borrowed from a friends buisness. The saw had been sitting in cold storage for the last 2-3 years. They have a duplicate in their shop that i have used several times. He said the only way he would need it back, is if something happened to the other one. Based off what i have read about doall equipment, i dont thik this will be a problem.

Anyways I want to get the saw usuable without changing out the motor or controls, in case i have to take it back. So some type of phase conversion is what i need....

Please let me know your thoughts.

I assume Purdue will want to be able to return the Band Saw ready to install in his freinds business.

In that case, he will want a reasonably priced solution that will not cause his freind grief if and when the saw is returned.

My suggestion is to reconnect the motor for the lower voltage. The only expense should be labor and maybe a few wire nuts.

Reconnect the control transformer for the new primary voltage. The only expense should be labor. Possibly he might need les than a fathom of wire.

Replace the heaters in the motor starter with ones sized to the new current rating (see the chart in the picture) and keep the old heaters for use when the saw is converted back to the original voltage. An envelope or baggie, properly labled, in the control box will be fine (even though it is technically contrary to the code).

Use a Rotary Phase Converter, they can be assembled from Industrial Salvage Parts for reletively little or purchased. The phase convertor will be seperate from the band saw and can be used for other machines or sold if the loaned bandsaw is returned. You will need a 3 phase motor, a motor starter and some capacitors; all of which should be available from an industrial bone yard. Old lighting fixtures have large capacitors.

P.S. My wife asked if you went to Purdue, she did.

 

[onewaydave]

Last post 7 months ago and I'm still holding my breath as to what PerdueSD did/will do. How about an update?

Me. I run a PM 72 tablesaw 3 ph off a RPC I built. I was given a 35 HP 3 ph motor from an old grain elevator (scrounge the agri and other industrial salvage yards), robbed some capacitors from dead ACs (scrounge the dump), some loose wiring and conectors. I bought a steel cabinet for $75 (out of a demolished feed mill) and a relay thingy (new)for $35. Instructions came from the almost always wrong internet. To run the other 25 HP worth of 3 phase I'd just need to add a 3 ph distribution/cb/service pannel.

 

[PurdueSD]

Honestly, i haven't gotten to it. I know, i know.... sad isn't it. Hopefully soon though...

 

[930dreamer]

I'd look into building a rotary phase converter. The practical machinist forum is a great place to start. I built mine to start an air compressor with two 3hp 3 phase motors.

I had very limited wiring experience, but got it done being very careful. These pictures are the RPC in it's crude form. I bought two spools of #8 wire over the years and several 3phase motors.

I used a pony motor(gas air compressor) to spin the 10 hp idler up to speed then applied 240 V single phase on a 50 amp circuit, this reduces the starting amps on the service. Normally a 1/4 - 3/4 hp single phase electric motor is used as the "pony motor", I didn't have one available at the time. An RPC can be built with a self starting control system also. I just wanted to see if I could make it work, and I did.
This clip shows, spinning the 10 hp idler and listen for the circuit being energized.
<embed width="600" height="361" type="application/x-shockwave-flash" allowFullscreen="true" allowNetworking="all" wmode="transparent" src="http://static.photobucket.com/player.swf?file=http://vid228.photobucket.com/albums/ee137/3CL1/comp5.flv">
Compressors starting. Very crude set up. When the RPC starts so do the compressors. More work to be done

 

[Steve from Socal]

A VFD or rotary converter would be the better choices but, depending on what you are cutting a simple static could be all you need, this is essentially a few run capacitors. I have run my saws main motor 3HP with a static and have had few issues. The issues are if you turn the saw on and off several times in short order and if you were to "need" the full HP to make a cut. My saw has a hydraulic system and the air blower driven off the main motor and even with a much higher parasitic load, the hydraulics, I have not had an issue with blade HP. To run the saw on low voltage 230~240 you would need an overload and fuses for the higher current.

Steve

 

[rwhite692]

I don't technically own the machine...yet. It is borrowed from a friends buisness....

....Anyways I want to get the saw usuable without changing out the motor or controls, in case i have to take it back. So some type of phase conversion is what i need....
.

If I were you, I would pass. Since you can't / shouldn't make any modifications to the saw.

Unless you can get yourself a phase converter setup free or on the cheap, you are going to spend probably at least a few hundred bucks to get setup with a converter to operate this thing, then, if you have to return it, you are stuck with a phase converter you (probably) have no use for.

Unless you have a real need for a monster saw like this, I think you would be better off to put a few hundred bucks into buying a (smaller) bandsaw that runs on 110 or 220, that you can actually own...

 

[PurdueSD]

If I were you, I would pass. Since you can't / shouldn't make any modifications to the saw.

Unless you can get yourself a phase converter setup free or on the cheap, you are going to spend probably at least a few hundred bucks to get setup with a converter to operate this thing, then, if you have to return it, you are stuck with a phase converter you (probably) have no use for.

Unless you have a real need for a monster saw like this, I think you would be better off to put a few hundred bucks into buying a (smaller) bandsaw that runs on 110 or 220, that you can actually own...

I guess i could have mentioned that now the saw is officially mine for good, but thanks for the advice anyhow!

 

[rwhite692]

Congrats, that is one hell of a bandsaw. Definately worth investing in a phase converter, now that it is yours for sure. Good luck and let us know how you decide to proceed!