Replies

1. 
   mlbfreestyle | Dec 03, 2003 04:05am | #1

   I think you mean 3 phase?

   A 3 phase, 480 volt motor is usually more efficient.  They also do not require a centrifigul switch or starting capacitor like single phase motors do.  By running at a higher voltage, current draw for any given power is lower; thus losses due to wire resistance is lower.

   I would not normally think that a bandsaw would be a prime candidate for a 3 phase motor, unless it was a large machine and/or would be subject to long run times.

   The rotary converters you may be talking about introduce some problems of their own that might offset any benefit from using the 3 pahse motor.  Besides, there will be some running losses associated with the converter.

2. 
   triplenet | Dec 03, 2003 06:45am | #2

      I had a large rotary converter to run larger commercial equipment.  Unless I had 3 phase service, I wouldn't do that again.  It seemed a real drag to start it and wait for it before using the tool (I'm talking a few seconds, but it got real irritating).  3 phase on bigger tools is the way to go, but I wouldn't consider a 20" bandsaw a candidate unless it's really cheap because it is 3 phase and most of us can not use it. 

    Last year I bought a new old stock Torrit dust collector with a 3 phase motor.  I bought a Baldor single phase and gave away the new 3 phase.  I did get about $1 for a couple of good 3 phase motors on an auction a few years ago, so knew what I was up against.

3. 
   user-5880422 | Dec 03, 2003 10:04am | #3

   for what it's worth, I have a minimax 20" with the 4.8hp motor. I can't imagine any meaningful benefit from getting the 3 phase option, especially if you don't have 3 phase power available.

4. 
   DavidxDoud | Dec 03, 2003 05:14pm | #4

   the main reason to get 3-phase on smaller home-shop type tools is the fact that you can get the tools used more cheaply than single phase - according to my electrician,  they do cost less to run,  but unless you are running multible tools continously,  you're not going to notice a difference -

   on a separate note,  your thread title mentions '2-phase' - - I was at an auction several years ago and examined a thicknesser whose tag very clearly stated '2-phase' - - I have never found anyone to explain exactly what this meant - - any experts here?

1. 
   numbfinger | Dec 03, 2003 11:30pm | #5

   Thanks guys...

   After doing some more research I think I'm going with the 3 phase machine. It's on a 24" bandsaw with a 4.8 horse motor.

   Since my dust collector is already a 3 phase unit, and since my phase converter would already be running the DC whenever the bandsaw is running - there would be little additional drain on the phase converter to run the bandsaw as well.

   A "professional" electrician specializing in large electric motors indicated that the biggest benefit will show up under heavy load - a single phase motor will tend to bog down more quickly than a similarly sized 3 phase motor.

   For what it's worth :)

2. 
   Elcoholic | Dec 04, 2003 12:14am | #6

   In the old days, 3 and 4 wire 2 phase systems were fairly common for manufacturing.  2 phase motors have 4 windings 90* apart.  For the most part the only system that remains are open delta systems where you use 2 transformers instead of 3 to get 86% of the rating of using 3 transformers.  You see them a lot on rural farm serices where the only thing they need 3 phase for is the water pump.  Saves money for the utility but volatge regulation isn't as good. 

   Another big advantage of 3 ph motors for wood working is they don't have a centifugal starting switch to wear out or arc.  The other stuff about load and overheating is BS.  Any induction motor meeting NEMA standards will deliver n horsepower at it's nominal voltage +/- 10% with no ill effect.  The main advantage of 3 phase systems is economic.  For a given distance and wire size you can carry 172% of the load that 2 wires will carry with the same voltage drop.  That's a great return on the investment for the 3rd wire or 50% more copper.

   Also keep in mind that standard frame motors can be traded in at your local motor shop.  I picked up a 5 hp 240V motor for $100 for my planer/molder.John O'Connell - JKO Handcrafted Woodworking

   Life is tough.  It's tougher if you're stupid - John Wayne

1. 
   mitch | Dec 04, 2003 06:06pm | #7

   you can't hardly give away 3ph motors can you?  i was at a big industrial auction yesterday and they had 150-200 small (1/2hp to a few 5hp) 3phase motors- probably at least half were baldors.  most of them new and unused or close to it.  the entire lot sold for about $700.

   m

2. 
   DavidxDoud | Dec 05, 2003 03:11am | #8

    

   In the old days, 3 and 4 wire 2 phase systems were fairly common for manufacturing.  2 phase motors have 4 windings 90* apart.  For the most part the only system that remains are open delta systems where you use 2 transformers instead of 3 to get 86% of the rating of using 3 transformers.

   thanks, - - what does that translate into in regards to hooking up such a unit? - - do you need 3-phase to run it? -

1. 
   Elcoholic | Dec 05, 2003 07:30pm | #9

   I don't know.  You might have to go to the IBEW retirement home to find an old enough electrician to find out:)  I'm fairly sure that using a second 2 phase motor as a rotating converter like is commonly done with 3 ph would work.  I've attached a reference from Ugly's.  It's a great little pocket reference for common electrical info.  Not sure if they're still in print but I got mine at an electrical wholesale house in '96.John O'Connell - JKO Handcrafted Woodworking

   Life is tough.  It's tougher if you're stupid - John Wayne