Hi Earthshaker, Hi Exo,
Thank you both for your replies.
Earthshaker, you are of course quite correct, you can directly
apply motion to the shaft, and a three phase motor will then
'spin up' to speed with a single phase applied.
I do not need the motor to do any more than to spin up with no
load applied, but i do not want to physically start it turning.
Exo, yes a capacitor is a solution, by feeding a winding via a
capacitor, a phase shift is introduced which will impart a
turning force to the rotor, enough to spin it up.
Why don't i want to use one ?
Well, i may have to.
But i am toying with other possible ways of introducing a phase
shift between windings.
I was thinking of putting two of the three windings in series
across the AC supply,
and putting the remaining winding across the AC supply.
I feel the inductance of the two in series would be different
to the inductance of the single winding.
This might produce a phase shift sufficient to impart a turning
motion to the rotor, and get it to spin up.
Then again it might not.
Or there might be other ways.
Or i may have to get a suitable capacitor.
If it can be made to spin up somehow, without any extra parts
i would be interested to find out.
Regards, John