On Sun, 04 Dec 2005 00:26:06 +0000, wrote:

On Thu, 01 Dec 2005 08:37:32 -0800, Eric R Snow
wrote:

Just wondering. I'm not gonna try it out. No sense in it. But here it
is: Three 240 volt single phase motors are wired together in delta,
the shafts are connected together in line, and the starting windings
are disconnected. If connected to a VFD, or any three phase source for
that matter, will they spin up? Will they maybe need to be rotated at
assembly 120 degrees to each other? I think it will work. Just idle
curiosity. We all know how dangerous that is.
Thanks,
Eric

It should work. The shafts would have to be rigidly joined
together so that there was no relative movement and the stators
lined up 120 electrical degrees apart (i.e 60 mechanical degrees
if it's a four pole motor).

A single phase single winding motor will not self start
because it is equally likely to rotate in either direction.
Without a starting winding to provide directional assymetry it
will just alternate about a stationary position.

With three coupled rotors with sequential three phase
oriented stators, the sequential torques will all add in the
phase rotation direction and provide the necessary starting
torque.

Once up to speed each motor will behave as a normal
single phase motor with the usual 100/120 hz vibration
transmitted to the stator. However if the the stators are rigidly
coupled the three sets of vibrations will cancel each other and
the complete assembly will have the same uniformity of torque and
freedom from vibration as normal three phase motor.

Jim


That's what I think too Jim. I guess I'm gonna have to see if I can
find three 220 volt motors ant try it out.
ERS