VFD by Hitachi courtesy of Drives Warehouse
For my UK friends: UK VFD's
Motor by Leeson
Sundries by MSC, a great company!
Contactors and assorted power-handling goodies by eBay
5 Bears Home


The prime mover and motor-vator, a Hitachi L100 VFD. Compact, intelligent, and packed with features that are a lot of fun to program and generally mess with. Cost, as of 2004, U.S. $300 at Drives Warehouse.
VFD Conversion!

I'd venture that roughly 1/2 of the visitors to this page are wondering "O.K. Neat. Now, what's a VFD?" A Variable Frequency Drive is used to control the speed of a 3-phase induction motor. It is FAR more than a fancy rheostat... controlling the speed of a 3-phase motor requires one to control the frequency of the voltage delivered to the motor, and this is not a trivial feat.

Goals: Initially, I was going to rather quickly slap this device onto an aluminum bracket and use it to feed the 1.5HP motor which powers my vertical mill. As I researched the technology, I realized that to do this correctly would require a bit more effort. On this web site, I was not going to do more than mention it in passing, perhaps post a picture or two, but I realized that it could become a "mini-project" in its own right, as there is quite a bit of interesting theory involved, as well as some mechanical and electrical work which might help others interested in such a conversion for their own machine.

Here then, are the goals at the outset:

  • Remove the original 1.5HP Chinese motor from my mill.
  • Replace it with an inverter-duty 2HP Leeson motor. (C6T17FC9F) Horsepower upgrade!
  • Engineer a remote console, to take advantage of all the cool VFD uProcessor magic.
  • Install a true electrical box for the mill to contain the wiring rat's-nest.
  • Replace my current shop 3-phase fused safety switch with a proper magnetic contactor.