On 2013-11-17, BobH wrote:
On 11/16/2013 6:50 PM, Ignoramus26083 wrote:
So, I have been buying, selling and scrapping 3 phase motors in the
last couple of years. I even made (and sold) a 15 HP phase converter a
couple of months ago. That worked out great financially.

All of this made me think: what exactly is the difference between a
motor and a generator? Can a circuit of some kind be added to a
regular 3 phase motor so that it converts mechanical energy input into
electrical energy output?

For example, a phase converter is actually a "generator": if two of
its "legs" are excited with single phase input, it "generates" third
phase that is shifted 120 degrees.

This, obviously, does not qualify as a standalone generator, since it
requires snigle phase input on L1-L2.

But can this motor somehow excite itself to generate electricity?

I think that they can, but with some issues. You have to spin them up
with externally supplied power, or at least get it biased up, so it
generates the stator field. The power factor sucks.

You spin a generator with mechanical power, for example a gasoline
engine.

Look up self excited induction generator or self excited squirrel
cage generator. A solar energy place I talked to a few years ago was
planning on using them. In the process of studying for the
interview, it appeared to me that there are several better choices,
but they do work.

I believe that if I excite one leg with DC, it will statr producing
AC. Right?