OK, is it true that when you only have a single phase motor, that when turning at high speeds that there is a just barely perceptible modulation of the workpiece as it turns, caused by the 50 Hz excitation?
I was told this some years ago, but being somewhat of a cautious person, I've never run the lathe at its top speed.
All motors including 3 phase ones, will exhibit that to an extent. 3 phase obviously reduces the problem, but so does the inertia of pulleys, spindles, lathe chucks etc acting as a flywheel to average out the motion.
Andrew
I didn't do any heavy machine stuff at Uni (all light current electronics) but I thought that the idea of 3-phase was constant power delivery?
But nothing is perfect - the motor construction and wire winding won't be absolutely symmetrical.
Andrew
With a single phase motor that had no run capacitor or shaded pole, the torque would drop to zero 100 times per second. With a run capacitor or a shaded pole, the fluctuation is a lot less, but still substantial.
With a three phase motor the deviation is only a few percent.
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