More VFD questions (was Re: VFD recommendations for Bridgeport...)

As long as there has been a lot of VFD questions lately... the last thing
I need to do to make my series II Bridgeport useable is get the 3 phase
motor situation under control. I have a home made rotary converter, but
it's not well assembled (yet). I also have a brand new Baldor BDI1100
220VAC in single phase 2 HP VFD, and a 4 HP motor on my Bridgeport. What
would be the problem with using it to run my 4 HP? It has an over current
fault output (a similar manual but only says 1 HP is located here:
http://www.baldor.com/pdf/manuals/71100-1296.pdf). Would the 4 HP motor
have too low of an inductance for the 2 HP VFD? If so, what if I wired up
the 4 HP motor for 440 VAC (the 3 pairs of windings in series rather than
in parallel) and only ran the frequency to 40 or so Hz for 220VAC
out? This should have 4 times the inductance then when wound in parallel
for 220VAC, and keep the volts/hz ratio about correct.. O.K., now here's
the biggest question: can I run my 4 HP motor in "half winding" mode (think
8 wire steppers)? I believe this will have the same inductance of a 2 HP
motor, and would put 220VAC across the half winding, just like it would
expect to see. The only problem I can see is what if the two half windings
per phase were located at different positions, rather than
overlapping. Any thoughts? If I get some free time to play in the garage,
I'll try this out on a 1.5HP motor I have kicking around. Just have to
wire in some 220VAC outlets in the garage...

Thanks for your time,

- Steven Ciciora


At 09:43 PM 3/12/2004 +0000, you wrote:

>I'm looking at the inverters from WWW.DRIVESWAREHOUSE.COM.
>Unfortenetly, thier tech department cannot help too much....
>
>the machine is an older Bridgeport Series 1 with a Boss 3 controller.
>I just ordered 3 Gecko 201s yesterday for the machine with hopes of
>using as much of the existing Boss 3 controller and powersupplies as
>possible.
>
>for the VFD, about all I know to look for is 230v single phase IN and
>230v 3 phase OUT and I'm guessing 2hp....would it hurt to spec a
>slightly higher hp VFD such as 5hp for my mill??
>
>thanks,