Method and apparatus for transducerless position and velocity estimation in drives for AC machines

The motor drive system comprising:

• (a) an induction motor including a stator with a plurality of stator windings thereon, and a squirrel cage rotor mounted for rotation within the stator, the rotor including means for providing impedance as seen by the stator windings which varies as a function of the rotational position of the rotor comprising a rotor body with a plurality of conductive bars extending through the body at spaced positions about the periphery of the rotor, and wherein slots are formed in the rotor body above each conductive bar, and wherein the slot above selected conductive bars are at least partially filled at regularly spaced positions around the rotor, with the slots above the conductive bars between such filled slots having lesser or no filling of the slots to thereby provide leakage inductance which varies as a function of rotational position of the rotor;
• (b) drives means, connected to the stator windings, for providing AC drive power to the stator windings at a fundamental drive frequency of the motor and for also providing power to the stator windings at a signal frequency which is substantially higher than the drive frequency;
• and
• (c) means for measuring the response of the stator windings to the signal frequency power to determine the variation of the response as a function of time during operation of the motor whereby the angular position or the speed of the rotor or both can be determined.

The motor drive system comprising:

• (a) an induction motor including a stator with a plurality of stator windings thereon, and a squirrel cage rotor mounted for rotation within the stator, the rotor including means for providing impedance as seen by the stator windings which varies as a function of the rotational position of the rotor comprising a rotor body with a plurality of conductive bars extending through the rotor body at spaced positions about the periphery of the rotor, and wherein the conductive bars change in cross-section from bar to bar, decreasing from a maximum cross-section bar to a minimum cross-section bar and increasing back to a maximum cross-section bar in a pattern repeating around the periphery of the rotor, to thereby provide rotor resistance which varies as a function of rotational position of the rotor;
• (b) drives means, connected to the stator windings, for providing AC drive power to the stator windings at a fundamental drive frequency of the motor and for also providing power to the stator windings at a signal frequency which is substantially higher than the drive frequency;
• and
• (c) means for measuring the response of the stator windings to the signal frequency power to determine the variation of the response as a function of time during operation of the motor whereby the angular position or the speed of the rotor or both can be determined.

The motor drive system comprising:

• (a) an induction motor including a stator with a plurality of stator windings thereon, and a squirrel cage rotor mounted for rotation within the stator, the rotor including means for providing impedance as seen by the stator windings which varies as a function of the rotational position of the rotor comprising a rotor body and a plurality of conductive bars extending through the body at spaced positions around the periphery of the rotor, wherein slots are formed in the rotor body above selected ones of the bars at spaced positions about the periphery of the rotor with no slots formed above the bars between the bars having slots thereover, to thereby provide leakage inductance which varies as a function of the rotational position of the rotor;
• (b) drives means, connected to the stator windings, for providing AC drive power to the stator windings at a fundamental drive frequency of the motor and for also providing power to the stator windings at a signal frequency which is substantially higher than the drive frequency;
• and
• (c) means for measuring the response of the stator windings to the signal frequency power to determine the variation of the response as a function of time during operation of the motor whereby the angular position or the speed of the rotor or both can be determined.

The motor drive system comprising:

• (a) an induction motor including a stator with a plurality of stator windings thereon, and a squirrel cage rotor mounted for rotation within the stator, the rotor including means for providing impedance as seen by the stator windings which varies as a function of the rotational position of the rotor comprising a rotor body and a plurality of conductive bars extending therethrough at spaced positions about the periphery of the rotor, wherein a slot is formed in the rotor body above each bar, wherein the depth of each slot varies around the periphery of the rotor, to thereby provide leakage inductance which varies as a function of the rotational position of the rotor;
• (b) drives means, connected to the stator windings, for providing AC drive power to the stator windings at a fundamental drive frequency of the motor and for also providing power to the stator windings at a signal frequency which is substantially higher than the drive frequency;
• and
• (c) means for measuring the response of the stator windings to the signal frequency power to determine the variation of the response as a function of time during operation of the motor whereby the angular position or the speed of the rotor or both can be determined.