help on deciding about rotarty phase converter for mill

Kelvin · March 16, 2008, 09:04:49 AM

Howdy all,

Still tossing around the idea of selling the 2003 LT40G25 gas mill and going with an older, cheaper electric to free up some money to pay some of the bills around here. My question is about rotary phase converters. Most woodmizer LT-40s that i'm looking at have a 25hp motor. I have 200 amp service panel in my sawmill shed and i bought a 40hp motor to be my idler motor. I found these electric motor starters on my craigslist, do i need these to help build my converter? I built a 15hp coverter in my barn, and just use a momentary switch to jump it spinning, would i be able to do the same with 40hp, or should i buy one of these starters? Are they just for starting on 3 phase? I noticed that to convert a gas LT40 to electric, woodmizer sells the electric motor and a starter(which is about $1200) Is this needed/helpful for my phase converter?

"Kelvin I Looked at you web site--very nice. I am a woodworker so I can appreciate what you have done. I also help out a friend of mine with his portable sawmill here localy.
To answer your questions- these starters will work great for you, they are off of 40hp A/C compressors. They were scrapping the units and I am like you I like to recycle.
I have three of the Cutler Hammer (white) and 2 of the Furnas and they are all like new. $50ea.
Let me know if you are intrested John "

I know a bunch of you guys have info on working on these things, so any help would be good. I'm trying to do this on the cheap, otherwise i would hook up to the three phase on the line 100' feet from my barn, but the power company wants over $5500 big ones. Dorks. Funny, if you are big they hook you up for no charge, but small and you pay. I guess they figure you will go under and stick them with the equipment, which is possible for me. I wonder if the whole neighborhood will dim out when i start my mill going. I ordered "heavy 200 amp service" and the supply lines looked a lot beefier than standard residential. THe panel on the house is twice as big as well.

THanks guys,
kelvin

Ironwood · March 16, 2008, 09:27:11 AM

You can not simply try to spin it (the slave motor) with a mag starter, you need a bank of capacitors and two swithes to throw the capacitors out of the system once the slave motor is spinning. There are two other options, one you spin it manually with rope to start it (or a smaller single phase motor with "slip belts" pulling tension to get the slave moving) then simply throw the power to it, OR put a adjustable timer inline to throw the capacitors out of the system (this is the most complex) and this is what I currently have.

Ironwood

gharlan · March 16, 2008, 09:34:27 AM

Kelvin, The starters for the motor is usually a device that has the overload protection as well as a low voltage control for the motor. I do not think you can use one to start your add a phase if that is what you are asking. If you want to do the add a phase on the cheap all you need to do is have a way to get your add a phase motor spinning and turn on the single phase to it. If the motor spins easy enough you can wrap a pull rope around it and pull it like a lawn mower to get it spinning. Once it is running you use the unused three phase leg from the motor to add your third leg for your mill. I also do not think you will have any trouble running the 25 hp on a 200 amp service. I have the same and run several thirty's at the same time with out any problem. Good luck Kelvin Gary

fencerowphil (Phil L.) · March 16, 2008, 04:58:15 PM

During the last thirty to forty days:

Two different customers said they would be bringing me logs to saw
at my site. They would have totalled about $700 worth of sawing.
Neither one ever showed.

I had the opportunity to saw at three portable sites where I did not
have to worry about my own clean up. At those three sites
I have done about $5500 dollars worth of work , either
just staight out sawing, or in sawing for logs that I,
in turn, sawed and sold to four other customers.
The saw is still set up at the third of these three sites. The
farming family has about eighty logs and wants primarily big
lumber: 22ft. long 2X8s and 1X8s. My pallet wood customer
is due now to move his trailer to that site (45 miles from his
shop!) so that I can sell even more wood that I am cutting at
someone else's site and which they will clean up!

Gosh I wish I was electric, so that I could not have gone for these jobs!

Phil L.

Ironwood · March 16, 2008, 06:20:22 PM

GOOD POINT PHIL.

Ironwood

kelLOGg · March 16, 2008, 08:34:35 PM

Kelvin,
I have a little experience in making a phase converter for a 5 HP planer using a 7.5 HP idler. I read a great deal on it from this forum and cited web references and found the pros (cheap) and cons (inefficient) of a DIY system. The idler motor does not operate with no cost - it (mine) warms up considerably which is $ lost and does not provide balanced voltage for all 3 phases (more lost $) . The imbalance probably gets worse as the load changes. Since I am only a serious :D hobbiest I figured this would not matter too much since I would not be using it daily. If I was in milling for my living and running a mill most of the day I would want the most efficient I could get which would be a commercial unit that provides balanced voltages as the load changes. That's probably the next best thing to the utility. Wow! $5500 for 100 feet!

Bob

Woodchuck53 · April 08, 2008, 06:04:02 AM

Morning Kelvin, that cost sounds about right here in la, also. I wanted to go to 3 phase. 1 extra pole and 125' plus the asst. panels well I couldn't do it.7000.00 is alot of money. Ended up buying a rotary phase from comm. 7.5 only drive a engine lathe and air comp. The cost was in my range 425.00 and the idle motor doesn't run the cost to high on extra electric. Am anxious to read more on this subject. Have a good one. Chuck

Ironwood · April 08, 2008, 08:34:50 AM

You know the one thing you guys haven't talked about is the HUGE increase in electric cost IF you go full three phase from the "pole". Here in western Pa. it will cost you $300 per month minimum, and then you are on a DEMAND METER$$$$$$$$. and we have relatively cheap prices. SO, keep that in mind when considering how ineffiecent and "wasteful" that idler is. There is only what I call "bad math" when going away from creating your own 3 phase.

Ironwood

oakiemac · April 08, 2008, 04:56:58 PM

For what it's worth, I run two pieces of equipment off a 25hp phase convertor. I run a rip saw with a 15hp motor and a 5 hp feed motor and I run (not at same time) run a moulder with a 10hp, 5hp and 1.5hp motor. My service is a 200amp main panel.

So Kelvin I think you will have no problems with the 200 amp service but you will need motor starters to start any motors including the phase covertor. You will also want protection in case you loose a phase which will cause your motor to run at much higher current and possibly burn up.