Phase converter

[Lloydthumper]

I was wondering if I could run a band saw off of a static phase converter or would I need to build a roll phase converter I can get a 3phase motor for free can chose from many different sizes to build a roll converter but I have never built one. I don't think it would be to hard but If I could just buy a static coverter for $100 and it work fine I would do that. The band saw has a 3hp 208/230 motor on it. I can buy another motor but that I think will cost more than I want to spend on a single phase motor for it. Any advice would be appreciated.

 

[toadjammer]

You can probably build a rotary for less than $100 if the motor is free and you shop around. The nice thing about a rotary is you can instantaneous reverse machines which is nice for lathes and mills if you decide to expand in the future. Also the static convertors are generally speaking just motor starters and after the motor is started either the third phase drops out or is run off of a capacitor. They are not that hard to build either.

 

[sneezer41]

Yeah, a rotary phase converter will serve you for years, all you need is a little single phase motor[usually free for the taking] and the bigger 3 phase, coupler, switches

 

[swampymarsh]

Do a search on phase converters on the www. You should be able to find resources on how to build static phase converters and save you some cash.

Dave

 

[tigmusky]

Lloydthumper, I just went thought the samething.need 3ph got some motors for free....... anyway i found this guy in az. for $125.00 he sent me a box . all you have to do is run two hots in and three wires out to your idler then from the idler to your bandsaw or what ever.. easy and pretty cheap...If you like more info pm me and i will get his number. I would post the guy name and number (to help him out.. throw him a bone) but this guy is slower than the 2nd comeing of jesus. daye

 

[W-Cummins]

Here is a link to one of the best sites about making phase convertors. You can make one for under a dollar if you have an extra 3 phase motor (using a rope to pull start the convertor! Of course it's not an elegant solution but it works)
There are directions there to make self starting and other styles of rotary converters. Plus information about building static converters too.

William....

 

[Lloydthumper]

Thanks Guys I haven't had time to read through everything yet which I may find my next answer is do I need a motor equal to the driven motor or do I need one larger to compensate for start up. Lloyd

 

[W-Cummins]

Thanks Guys I haven't had time to read through everything yet which I may find my next answer is do I need a motor equal to the driven motor or do I need one larger to compensate for start up. Lloyd

I would look for a 5hp 1725 rpm motor to make your converter. Probably a little larger than you would need just to start the BS, but more useful, as it would be able to start your band saw and other tools that you will get now that you can run them!

William...

 

[OldCarGuy]

There is another solution to running a three-phase motor off of single phase service. And a rotary phase converter may not be the best solution for your particular situation of running a single piece of equipment in your garage.

Although a rotary phase converter works best for me. I have 12 pieces of equipment with a total of 24 motors that run on three-phase in my garage that can run from a single rotary phase converter. However do you want to bother starting up and the added cost of running an idler motor anytime you want to run your band saw? I would suggest a dedicated Variable Frequency Drive (VFD) that would cost a few hundred dollars. The other advantage of a VFD would give you the ability to run the saw at different rates at a turn of a dial.

 

[Lloydthumper]

The bandsaw is a 3hp delta rockwell verticle bandsaw. I always look for the most economical but best way of doing something. I figuared with the motor being free I could buld the converter for very little. Although I do like the idea of a varible frequency drive and being able to adjust the speed and I have installed a hundered of them at work on various machines If I was going to spend a couple hundered dollars on a frequency drive It would be best to go ahead and buy a single phase motor.

I guess I am not sure how the VFD would work as well for a phase converter with it being a 3 phase drive can you elaberate on that some old car guy. Maybe a drawing or a drive type or drive # I have delt a lot with seimens drives and aeg and keb drives. Thanks Lloyd

 

[OldCarGuy]

A VFD that I speak of is a type of phase converter that you can power the present three-phase motor that you have in your band saw.

http://www.driveswarehouse.com/Drives/AC+Drives/Phase+Converter+VFD/

 

[Steve in Mi]

A 3 HP single phase motor @ $150.00 plus S&H

http://cgi.ebay.com/3-HP-motor-sing...ZWD1VQQ_trksidZp1638.m118.l1247QQcmdZViewItem

A rotary converter is basically a static converter with the addition of an idler motor. I've not messed with static converters non would I as the rotary converter is a much better/more efficient way to get 3 phase power IMO. I have built some rotary converters of 5 HP and less and didn't bother to match legs (voltage wise) as some do. I found the higher RPM idler motors to be close enough. Today I use VFD's not only because they are very efficient converters of single phase power to clean 3 phase (matched legs) power but they offer variable speed and with the proper breaking resistor can give plug reversing (important to lathe threading, taping operations and safety stops). A VFD can allow you to transform a wood cutting bandsaw into a metal cutting bandsaw. Back and forth with the twist of a knob and possibly a blade change.

Disclaimers: Not all vfd's allow for single phase input. Most vfd's after ~1998 can be wired for single phase input but require some derating of output. Some vfd's can output a higher voltage than input voltage (120 volt 1ph in and 220 volt 3ph out, 220v 1ph in and 440v 3ph out). There are some other oddities one can find and learn about if interested.

This vfd at $275. + S&H would be matched to your saw providing the saw is 220 volt and full load amps is less than 10.

http://cgi.ebay.com/3-HP-VFD-VARIAB...ryZ71393QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Have fun.

 

[W-Cummins]

Some vfd's can output a higher voltage than input voltage (120 volt 1ph in and 220 volt 3ph out, 220v 1ph in and 440v 3ph out). There are some other oddities one can find and learn about if interested.

I have seen the 120 to 240 volt models but I have never seen the 480v models do you have a link for one

William...

 

[qship510]

A VFD that I speak of is a type of phase converter that you can power the present three-phase motor that you have in your band saw.

http://www.driveswarehouse.com/Drives/AC+Drives/Phase+Converter+VFD/

OCG, my simple brain tells me to build a rotary converter at least 10HP so I can run 3 phase machines to my heart's content, but I saw a seller mention that his rotary converter was too big for his application. Can a rotary converter be too big?

 

[Steve in Mi]

OCG, my simple brain tells me to build a rotary converter at least 10HP so I can run 3 phase machines to my heart's content, but I saw a seller mention that his rotary converter was too big for his application. Can a rotary converter be too big?

Yes I heard the same comment many times that a converter can be too big and judging by those particular complainers I believe it. Also have it on good authority that a 5 hp rotary can run a combined load of as much as 20 hp if started individually and in the proper sequence. But your mileage may vary.

 

[Steve in Mi]

I have seen the 120 to 240 volt models but I have never seen the 480v models do you have a link for one

William...

And I recall you didn't see one of these either but I have them in my shop;

WTB 3 Phase, 115 Volt motor, ~1740 RPM, 1 HP or less

<HR style="COLOR: #999999" SIZE=1><!-- / icon and title --><!-- message -->Good luck, I have never seen one. 115V is NOT a normal 3 phase voltage. I also have never seen a transformer setup to convert to that voltage either.

I don't have a link but I think most vfd manufacturing companies could set you up with one. I have seen a few on ebay. If you go to the Practical Machinist site and search the VFD archives (~ 5 years back) under Steve Stube you will find a discussion about them and learn that Chris offered to modify at a reasonable fee some brands of VFD's to output 440 with 220 v input.

 

[Lloydthumper]

I also found this on ebay and I am intreigued to say the least. He has 576 positive feedback and the video's are cheesy but cool at the same time Just wondering if any one has tried or knows someone who has tried this method.
http://www.unique3phase.com/index.htm

 

[OldCarGuy]

My Power Distribution Center in my Garage Shop,,, 240 Volt 200 Amp single phase main load center. And a 100 Amp 240 Volt three phase load center fed by 1 5 HP and 10 HP Rotary Phase Converters. They are set up to run either one at a time or both in tandem for maximum three-phase output. The center top box encloses the switching relays so that I don‘t get any feedback to one of the RFC that is not running while I‘m running the other.

I now have a total 22 motors on 12 machines that can run off them. Ranging from 1/ 4 HP to 7.5 HP. I was told that my 7.5 HP lathe would require a 15 HP rotary inverter to run. But was told I could run the two inverter to achieve that rating. The fact is it will start up and run all day without any problems on the 10 HP inverter. In fact I neglected to switch over to the bigger inverter one time. And started and ran the 7.5 HP lathe for hours on the 5 HP RFC. Which I wouldn’t recommend. But it never caused any problems.

I also checked out your other concern about over sizing a RFC. Though I do know the answer because I do it all the time. I turned on both my rotary converters (15 HP total). And I went around my garage shop and ran one at a time 1/4 HP, 1/2 HP, 1.5 HP, 2 HP, 3 HP, 5 HP, and 7.5 HP motors. No problem. Then all running at a time,, runs fine. For the fun of it I had a total of 12 motors going at a time… still no problems. And the lights didn’t even dim!

I understand that sizing a three phase converter only applies to static converters and VFD….

 

[kvom]

I presume that most of the draw on the inverter occurs when a motor starts up. Once it's running it needs a lot less energy.

 

[W-Cummins]

And I recall you didn't see one of these either but I have them in my shop;

No, I had not, and I still have not. Did you ever purchase another one, so you don't have an orphan? I never said that some one didn't have a short run of weird stuff, if you have enough $$ and time some one will build you almost any thing!



BTW This guy had not seen any either and he works for a rather large motor manufacture

I will have to put my foot in my mouth here, I did some further digging and these motors are not 3Ø, but rather single, they are classified wrong in our web-xreference system. When I entered 3ph 115V into the search system, the motors came up, but if you go to the catalog page, they are actually single phase (I looking into our engineering system to verify). Sorry about that.

A related question, what controller do you have access to? I'd be surprised if its a 115V unit.

Also what brand/model is the motor you have on your lathe now? I checked a couple competitive sites and do not see that spec either.

Jake

I don't have a link but I think most vfd manufacturing companies could set you up with one.

I'm sure for enough money "some one" could and probably would make you some, if you purchased enough of them, to make their time worth it. I'm sure that if you called any of the big manufactures ( A&B, Hitachi, Semens, Baldor, etc. ) and asked them to make you ONE, they would get a good yuck out of it before they told you NO

I have seen a few on ebay. If you go to the Practical Machinist site and search the VFD archives (~ 5 years back) under Steve Stube you will find a discussion about them and learn that Chris offered to modify at a reasonable fee some brands of VFD's to output 440 with 220 v input.

SO... I need to search a 5 year old archive on some form, and find a guy named Chris to make me one??

I guess I'm not likely to ever see one of those either


William....

 

[Steve in Mi]

William, you're right.

 

[OldCarGuy]

I presume that most of the draw on the inverter occurs when a motor starts up. Once it's running it needs a lot less energy.

That is correct, a motor draws far more current on startup than when it’s running and not under a load. And the more motors that run a time the better and seem to balance out the phases. When starting a motor with a HP rating near the RPC's idler motor rating you can hear it strain. It will strain less with more motors running.

 

[W-Cummins]

William, you're right.

Quitter ....

Anyway I went and looked up the posting about the conversion on the drives, and it's an interesting idea, but beyond the "Normal" DIY project. The 2 speed motor application is one that might warrant the conversion (be sure to shut off the power from the VFD BEFORE you switch the speeds on the motor ). I think that for most the boost of a 240v to 480v transformer would be more practical though. Then you could use an off the shelf VFD ( as long as it didn't freak about the loss of a phase and shut down). I'm using a VFD drive in the reverse mode 480V to 208V and it works great for that and frees me of having to run a 3 phase 35kva transformer 24X7. I'm also probably going to run another one when I get a cold saw as most of them are 240v not 480v

William...