Optimum efficiency rotary machine having synchronous operation at a selectable speed

In a three-or-more phase machine with a stator having a plurality of windings thereon, each stator winding producing a magnetic field when voltage is applied thereto, a rotor rotatably mounted with respect to said stator, said rotor having a magnetic field therein fixedly oriented with respect to said rotor, the rotor field being operative to induce a voltage in the stator windings when the rotor is rotating, and a power circuit for applying positive and negative voltage to the stator windings, switching transients beng produced when voltage is applied to and removed from a stator winding, a rotor position sensing circuit, comprising:

• a voltage detector connected across a stator winding, said voltage detector being operative only when the voltage across the connected stator winding is more positive than the amplitude of a negative voltage following the turn off of a positive voltage applied to said stator winding, said voltage detector producing a polarity signal when voltage across the connected stator winding is more positive than the amplitude of said negative voltage;
• a delay means responsive to said polarity signal to produce a delay polarity signal, said delay being at least as long as the time required for negative going switching transients across said connected stator winding to pass through the voltage range between the amplitude of said positive applied voltage and the amplitude of said negative voltage;
• a first gate means responsive to said polarity signal and said delayed polarity signal to produce a transient completed signal;
• a polarity detector connected to said stator winding for producing a sense signal when the voltage across said connected stator winding is negative;
• a slope sensor responsive to the voltage across said connected stator winding for producing an enable signal when said voltage across said connected stator winding is decreasing;
• and
• a second gate means responsive to said transient completed signal, said sense signal, and said enable signal to produce a reference position signal indicating that the rotor has a known positional relationship with respect to the stator.