According to william_b_noble :

"JB" wrote in message
...
Hi Guys,

Once again I am here with my hat in hand humbly requesting your
assistance. As some of you know, I am in the process of purchasing a
Colchester Circa 1960's MK 1 1/2 lathe. It has a two speed 5hp 3 phase
motor. Will I be able to run it successfully on a static phase converter?

you may find that a VFD costs about the same as a static converter (unless
you happen to have the parts and plan on building it yourself) - look for a
used one

Hmm ... a VFD is not likely to work well with a two-speed
three-phase motor -- unless you do all speed switching with the VFD.
You're not supposed to put the switch between the VFD and the motor, as
the voltage spikes from the switching can zap the output transistors of
the VFD.

Here is a place where I feel that a rotary converter
(build-it-yourself) would be the better choice. Or -- you could limit
yourself to one set of windings on the motor, and do all speed changing
with the VFD. For extreme cases (where you *really* need the higher
torque of the low speed, or the higher speed of the high speed), you can
stop the motor entirely (using the VFD's controls), switch to the other
speed at the lathe's switches, and then start the motor back up with the
VFD.

Good Luck,
DoN.

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