Jim Stewart wrote:
Jon Elson wrote:



Jim Stewart wrote:

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




I'm going to go against the grain here and say
that they might run.

You'd want them all to have similar or preferably
identical pole structures and you'd have to
"time" them by making sure that all of their rotor-
to-field relationships were the same after they
were coupled together (*not* 120 degrees out of
phase).



No, it won't work. The reason a 3-phase motor can start without a
start winding is because all three phases are applied to ONE ROTOR.

"Timing" the motors won't work. Induction motors don't have
any pre-defined poles on them until the rotor is excited magnetically
by the stator.


I'm still not convinced.

You may be right but I'm still not convinced.



So, prove it to yourself. (If these motors don't have a centrifugal
start switch and start windings, then they would start by shaded pole
design, which could be confusing.) But, 3 single-phase motors tied
together on a shaft are not one three-phase motor.

Jon