Voltage-controlled field-oriented induction motor control system

Claim 1

In an induction motor drive control system associated with an AC power supply applying to the induction motor a controlled AC voltage power supply as a function of a motor torque demand; the combination of: first means for providing a motor shaft position representative signal; second means responsive to a predetermined torque demand signal for providing a slip frequency representative signal; third means responsive to said first and second means for providing a reference frame rotation angle representative signal for said motor; means responsive to said motor shaft position representative signal and to said slip frequency representative signal for providing a direct and a quadrature voltage signal defined by reference to said reference frame; means responsive to said reference frame rotation angle representative signal and to said direct and quadrature voltage signals for generating AC voltage representative signals for said AC power supply; with said direct and quadrature voltage signals providing means providing a direct voltage signal v ds , where: v.sub.ds =1-(ω.sub.m +ω.sub.s)ω.sub.s T.sub.1 T.sub.2 σ and a quadrature voltage signal v qs , where: v.sub.qs =(ω.sub.m +ω.sub.s)T.sub.1 +ω.sub.s T.sub.2 +T.sub.1 T.sub.2 σdω.sub.s /dt; and where: ω=electrical angular velocity of the reference frame; ω m =electrical angular velocity of motor shaft; R 1 =stator resistance per phase; R 2 =rotor resistance per phase; L 1 =three-phase stator self-inductance; L 2 =three-phase rotor self-inductance; M=three-phase stator/rotor mutual inductance; ω s =slip frequency; σ=(1-M 2 /L 1 L 2 ); T 2 =L 2 /R 2 ; T 1 =L 1 /R 1 ; n=pole pair number of the machine; and p·=d/dt; with means for imposing a maximum on the rate of change of said predetermined torque demand signal being interposed between said predetermined torue demand signal and said second means; with said AC voltage power supply being controlled by said AC voltage representative signals, thereby to dynamically generate a torque proportional to said predetermined torque demand signal when said predetermined torque demand signal changing, while not exceeding said maximum rate of change.