Questions for anyone running a LT40 on electric rotary converter

[Kelvin]

Howdy all,
I visted a guy who had a dedicated slabber saw on a rotary phase converter.  He said it would "overload and start running on single phase power, thereby loosing power"  for whatever that means.  His rotary phase converter was big enough and professionally installed.  He said it wouldn't work for the load on the saw (big 6' long chainsaw slabber with electric drive motor)  I'm thinking of getting a 15hp LT40 and only have a converter to run off from.  No option for real 3 phase.  Does anyone have any experience with doing this?  I know its not as powerful as real 3 phase, but does it work?  I will be needing every horse out of my mill as i'm trading in a 25hp gas, so i've heard a 15hp elec. has similar torque to something like a 25hp gas motor.  Hate to loose any speed as that saw was slow enough.  Any thoughts?
Thanks
kelvin

[Bibbyman]

A lot of people are running 3ph motors on phase converters.  We have a 25hp LT40 Super,  a 10hp edger, 7.5 hp pump unit,  and 10 hp jump saw running on a 50 hp phase converter.

Here is a link to something I put in the Knowlege Base that tells about everything about our setup.

https://forestryforum.com/tips/tips.cgi?display:1048263552-19768.txt

A rotay phase converter is not perfect but if done right, works well.

[Dave Shepard]

I have run a '94 LT40 with an Onan 24HP, and a '92 LT40 with the 15HP three-phase. These mills are absolutely identical, and will produce the same amount of wood. You won't be loosing anything by going to the 15HP three-phase. I'm actually running the electric on 208volts, so it isn't putting out full power, so it would be even better with full voltage.

As far as the phase converter, I'll let Bibbyman fill you in better on them. As far as I know, you shouldn't have any reduced output from your three-phase motor. The inefficiency is in the converter. It takes more electricity to make the motor run through the RPC, than if it it was hooked directly to the grid, however it's a small price to pay for three-phase power. ;)


Bibbyman beat me to the post. :D

[Kelvin]

Thanks guys, its good to know that it works.  I assume the guy i met just had too big a load for his motor.  he blamed the converter, but i wasn't certain about that.  I'll read bibbyman's converter info and see about how big to build mine.  I have two motors, one is 40hp and one is 20 hp, so i've got to figure which might be a better setup, and give me future power as well.
Thanks
kelvin

[logwalker]

Kelvin, I am running a 1994 off a well designed 20 hp unit. It works perfectly with plenty of power. I put my speedo unit on the idler and never see it slow more than 2% from no-load to full-load. Don't hesitate to try it. Joe

[schmism]

if your phase converter is properly sized you will see no difference between it and grid supplied 3phase. (other than total Kwh usage)

[Bibbyman]

Thanks guys, its good to know that it works.  I assume the guy i met just had too big a load for his motor.  he blamed the converter, but i wasn't certain about that.  I'll read bibbyman's converter info and see about how big to build mine.  I have two motors, one is 40hp and one is 20 hp, so i've got to figure which might be a better setup, and give me future power as well.
Thanks
kelvin

Now I know nothing about home built units.  I went store bought.  Between Wood-Mizer, Ronk and the local utility,  they got me set up.  Almost 7 years and 3600 hours on the mill and all I've had to do with the phase converter is give it a squirt of grease once a year. 

[logwalker]

"Almost 7 years and 3600 hours on the mill and all I've had to do with the phase converter is give it a squirt of grease once a year.  "


And a small one at that.... ;)

[scrout]

Just saw this today on my local Craigslist:

http://portland.craigslist.org/yam/tls/913408890.html

You might check out Surplus Center.
You can get a 40hp 3 phase for $999 and build your own.....

[bandmiller2]

Kelvin,I'd believe the bibster and joe.Possibly the guy you know has something hooked up wrong.Many licensed electricians don't really know that much about motors,let alone phase converters.Outher than running two motors to use one they work well ,been running a milling machine for years with a simple one I made.Frank C.

[Larry]

Thought I would mention you can get in serious trouble with your power company if you cause a voltage drop which causes other customers lights to dim.  That's pretty easy to do.  They don't have to upgrade there facilities to meet your needs...they just disconnect you (which they can legally do).  When I was in north Missouri I melted down a 25kva transformer which only served me but the power company replaced it with a 35kva...no questions asked.  In Arkansas  I had to sign a statement saying I would not run a motor with more than 5 horsepower before they would give me juice.

A conversation with your local power company would be a good place to start...just don't volunteer to much information.  If you see fit to proceed a properly engineered RPC...think soft start on higher horsepower motors, could eliminate problems down the road.