voltage in the machine has a waveform which approximates a sinusoidal waveform; and an angle ?? whose sides are radii of the rotor passing through opposite circumferential ends of a surface of each permanent magnet facing the stator satisfies one of the expressions: θ≈n???τs +α, θ≈n???τs +β; θ≈n???τs +γ where n is a natural number, ??