Replies

1. 
   JohnWW | Dec 21, 2004 09:14pm | #1

   Alan,

   State of the art these days for lathes is to install a three phase motor and an inverter to control it.  The black box electronics in the inverter will take single phase power and tranform it into three phase with all sorts of options for speed control, braking, and torque regulation.  The price of inverters is steadily dropping, they are under $500 for units rated for 1 HP. 

   Although they make three phase motors designed for use with inverters, a standard motor will work fine unless you work it exceptionally hard.  Used three phase motors can often be found at a good price.

   John W.

2. 
   RickL | Dec 21, 2004 11:44pm | #2

   My local motor shop carries a Baldor inverter rated for a 1 hp motor for $250. You can program a lot of variations such as soft start and more than you could possibly imagine. It will actually double the rated rpm of the motor and the other unusual feature of the 1 hp rated unit is it will run a three phase 240 volt motor on 120 volt single phase.

3. 
   TKanzler | Dec 22, 2004 12:40am | #3

   Be advised also that a lathe is essentially a constant-horsepower load in the sense that the power at the tool tip can be about the same whether you're cutting a large bowl (high torque, low rpm) or a smallish spindle (low torque, high rpm).  Using a VFD to slow the spindle speed won't necessarily reduce the power requirement.  In fact, most turners seem to feel that more power is needed for large diameter work.  That translates to high torque requirements from the motor, but with reduced cooling capability due to it's lower speed. 

   That's why lathes with electronic speed control generally use oversized motors, as well as at least a couple of belt-drive speed ranges (to get into the general neighborhood via mechanical means).  The motor is sized for the torque requirement and it's ability to cool itself at the lower motor speeds, with untapped power reserves at higher speeds.

   Be seeing you...

1. 
   AlanMikkelsen | Dec 22, 2004 03:18am | #4

   Thanks all for the information.  There's also a letter with info in it in FWW that I received in the mail today. Alan & Lynette Mikkelsen, Mountain View Farm, est. 1934,  Gardens & Fine Woodworking, St. Ignatius, MT