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#128477 - 03/29/03 06:53 PM using old motor to transform 240v to 460v ??
Hillbillysawmiller Offline
Junior Member

Registered: 03/29/03
Posts: 6
Hello, I am new to this list and am not an electrical contracter or electrician. I have a sawmill and lumber business in the Missouri Ozarks. I have only single phase power with a 200 amp service at the end of a line. The area I am in is very rural with no electrical codes that I know of and no electrical inspections or inspectors. With my 200 amp single phase service I run a 40 hp on my sawmill, a 20 hp on my band resaw a 10 hp on my dust blower, Two 5hp and a 7.5hp on my molder, 5hp on my planer and a 5hp on my blower which pulls the shavings from around the molding and planing heads. All of these motors are 3 phase. To make the 3rd leg (manufactured leg) I use a 25hp 3 phase motor. I ran the 2 lines from the power company to my main disconnect and from there I used them as L1 and L2 when I wired them to my 25hp. For L3 I ran a wire from the 25 hp back into my main as if it were coming from the outside. From there I wired up all of my 3 phase motors as they would normally be wired. I use a small single phase motor to get the 25hp up to its running RPM. Once the 25hp is up to rpm I turn on the 25 hp motors disconnect. The 25hp will run at rpm from the 2 outside lines and while doing so will generate the 3rd leg. Now, The 40hp on my sawmill is to big to start by itself so I use a 10hp 3ph motor to get it up to rpm, then I shut down the 10hp, from that point I can start all of the rest of the motors on their own, even the 20hp on my resaw without dimming my neighbors lights. I do utilize several run capacitors. I had to set this system up this way for several reasons. #1 I cannot get 3 phase power out here. #2 I knew I could not use a regular rotophase as a friend of mine had tried to use one a couple of miles from here to start and run a 15hp motor on his band sawmill and it dimmed everyone's lights for a mile or two around every time he started the thing and so the power co op shut him down. That is the problem with bigger rotophases. Were ever you need them in rural areas you can't run them because they pull to much current when they and the motors that are connected to them start. Thus, I knew I needed a system with no start capacitors. What is neat is that this system works much better than I had thought that it would. For each motor I bring on line everything becomes more balanced and efficient (it costs approx $9.00 per day to run everything). The 40 hp on my sawmill has plenty of power does not bog down and does its job very well. What is really amazing is that my resaw has a computerized electronic controller that runs a small 3 phase motor that powers the variable belt feed. This device is supposed to be very sensitive. Yet I have never had a problem with it. In fact I have been running my operation with this set up for 5 years now and have had no problems at all, which is truly amazing since I bought several of the motors, disconnects and magnetic switches used. Now here is my dilemma. Back five years ago after I put this thing together the power company had qualms about hooking me up. In fact the engineer said that it would not work (not much of an engineer huh.) Anyway, I knew a guy in Arkansas that was running 3 times as much stuff as me with the same kind of set up at the end of a line on three 200 amp services. In fact he generated the 3rd leg for the entire thing through a 20hp delta Y motor ( I have to say though that when I leaned over to look at this motor a bead of sweet fell from my brow onto the motors case and it went psst and evaporated.) What is really wild is that once he brought several motors on line he could actually start a 50hp on this system without dimming his neighbors lights. He was very good friends with the guy who runs the electric coop down their. So, to make a long story short he had his electric co op guy talk to my electric co op guy and my electric co op guy reluctantly agreed to hook me up. The hook up was conditional though. The conditions were that I would be disconnected at the first sign of a problem and that I was to never ask for any more amps. Well I am at the point were I want to replace my existing saw mill with a scragg mill that runs from two 50 hp motors. I would also like to change out the 25 hp motor that I use to generate my 3rd leg with the 40hp that I have on my present saw mill. I believe there is a way to do this without getting another 200 amp service. I remember when I was a kid there was a sawmiller were I grew up who used an old 3 ph motor body to convert 220 3 ph to 460 3 phase. The thing, is I do not know how he had it wired up. I do remember that it was not running and he said it did not pull any juice. In fact I think the rotor had been removed. I can't be sure I was just a kid and the memory is fuzzy. Essentially I think he was using the stator as a transformer to convert the 220v to 460v so that he could run more horse power on less amps. If I could do what he did I could wire all of my motors 460 volt which would give me the ability to add the motors that I need to add and run them from my existing 200 amp service. I can not find any info on this anywhere on the internet or otherwise (I guess the guys who write the NEC haven't heard about it yet ;o). In fact I cannot find anything about the set up that I have and I have seen several half assed Mountain and farm boys use this kind of thing for different purposes. If any of you guys have seen this transformer thing maybe you could tell me how it is done. Or maybe someone knows of a device I could purchase to turn the 240v to 460v. It would save me the time of experimenting with a small 3ph motor until I do figure it out on my own. I apologize for this very looong post but I just wanted to put all the info in here so that you guys would know the whole background. Thank you for any help you might be able to give. I hope I have not made you guys cringe to much.
Hillbillysawmiller

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#128478 - 03/29/03 08:21 PM Re: using old motor to transform 240v to 460v ??
wolfdog Offline
Member

Registered: 10/24/01
Posts: 135
Loc: Dallas,TX
Sorry but going to 460 will not decrease your total load. Volts and amps are inversely proportional. Your motor will pull less amps at a higher voltage, but the load is the same.

Look at the label on one of your motors.
It will be listed as dual voltage - 230/460.
The amps go down when the voltage goes up. But it is the same size motor.

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#128479 - 03/29/03 08:28 PM Re: using old motor to transform 240v to 460v ??
zapped208 Offline
Member

Registered: 02/18/03
Posts: 201
Loc: Somewhere in USA
Hillbilly,- I have wired 2 new sawmills in my time, and also repairs in a number of other mills, all had 3 phase though. I would love to see your setup if I could ! Have you looked into getting a diesel genset for 3 phase? Your probably pushing the 200 A service pretty hard now. Thanks for the nice story!
_________________________
Shoot first, apologize later.....maybe

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#128480 - 03/29/03 09:30 PM Re: using old motor to transform 240v to 460v ??
resqcapt19 Offline
Member

Registered: 11/10/00
Posts: 2209
Loc: IL
The Table 430.150 FLA of all of the motors that he has running at the same time totals 238 amps already.
_________________________
Don(resqcapt19)

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#128481 - 03/29/03 09:46 PM Re: using old motor to transform 240v to 460v ??
Hillbillysawmiller Offline
Junior Member

Registered: 03/29/03
Posts: 6
Wolfdog,
I don't want to decrease my total load. I want to add two 50hp motors, remove a 40hp motor and change it out with the 25hp that I am using to create my third leg. At 230 volts all of these motors would pull to many amps. At 460 volts they would not. I know about the inverse relationship between amps and volts. I also know that volts X amps = watts. So if I can transform the 230v to 460v and add the other motors I would be using around the same # of amps but about twice as many watts. Does the 200 amp service or transformer limit the # of watts I can use in an hour, and if so would using twice as many as I am now exceed that limit?
Hillbilly

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#128482 - 03/29/03 10:20 PM Re: using old motor to transform 240v to 460v ??
Hillbillysawmiller Offline
Junior Member

Registered: 03/29/03
Posts: 6
zapped208
Thanks,
You are welcome to come see my set up anytime. I have thought about a generator but figured it would cost me allot more in the long run. I am not really sure how hard I am pushing the 200 amp service. I do not normally run everything all at once. Even when I do the motors are not under a very heavy load. The feed on my mill is not that fast and due to the accuracy of the band resaw we do not have to remove very much during planning and molding operations. If I were to get the scragg I would probably be running it by itself only one day a week. The scragg would have 5 times more production capability than the mill I am currently running. Do you know of any way to convert the 230v to 460v?
Hillbilly

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#128483 - 03/30/03 12:01 AM Re: using old motor to transform 240v to 460v ??
stamcon Offline
Member

Registered: 03/24/01
Posts: 322
Loc: So San Francisco CA
Hillbilly, how far away from you is the power company's transformer, that drops your service down to 220V? Are there any other users between the transformer and your mill?

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#128484 - 03/30/03 05:49 AM Re: using old motor to transform 240v to 460v ??
maintenanceguy Offline
Member

Registered: 12/02/01
Posts: 303
Loc: Southern NJ, USA
Stepping the voltage up after the poco's meter won't reduce the current draw before the meter.

I saw a similar set up in a shop in Lancaster PA several years ago many miles from any town. I didn't understand a bit of how it worked when I saw it but did some reading afterwards. It was pretty cool.

This was a machine shop with some pretty big lathes and shapers but not as big as your mill. I know that to start some of the bigger stuff, the shop owner first started several other pieces of equipment and then was able to start the big motors. Once the big motors were started, he shut everything else down and it worked fine.

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#128485 - 03/30/03 06:53 AM Re: using old motor to transform 240v to 460v ??
Hillbillysawmiller Offline
Junior Member

Registered: 03/29/03
Posts: 6
Stamcon,
The closest 3 phase that I know of is about 8 miles from my mill. There are probably around 40 houses between my mill and there including my own house which has a separate 200 amp service from the mill. I am not sure of the whereabouts of the transformer that drops the voltage from 460 to 230. Wouldn't that transformer be were the 3 phase ends? I am at the end of the power line about 1 mile from my closest neighbor. behind my place is 3,080 acres of private land on the other side of that is around 25,000 acres of national forest.
Hillbilly

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#128486 - 03/30/03 07:10 AM Re: using old motor to transform 240v to 460v ??
wolfdog Offline
Member

Registered: 10/24/01
Posts: 135
Loc: Dallas,TX
Think about your reply to me,

...twice as many watts....

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