> In recent years, motors have started to be designed for the non sinusoidal waveforms that come out of chopper power supplies.
From what i remember, square waves are better for a motor.
Thinking about it i see no benefit of it being sine (*with many poles, that is, as a square would shake the mechanical parts too much otherwise).
Depends on the windings. Synchronous motors have had windings designed for sq. wave drive for many years now, prominently for stepper, servo and BLDC motors. These still use some filtering to reduce the insulation stresses.
From what i remember, square waves are better for a motor. Thinking about it i see no benefit of it being sine (*with many poles, that is, as a square would shake the mechanical parts too much otherwise).
The trams here have 3-phase engines.