Abstract: A decogging feedback control for current source inverter motor drives uses a change of instantaneous torque feedback signal with no dc component that is a function of only the instantaneous pulsating component of measured torque. The change of torque signal modulates the voltage applied to the dc link and therefore the dc link current to materially reduce the detrimental cogging torque pulsations and stabilize the motor, and can be switched out at a low frequency above which it is not needed so that the motor can respond properly to rapid variations in torque.

Abstract: A method and circuit for calculating the instantaneous pulsating component of torque for use as a cogging feedback signal to stabilize ac motors at low frequencies. An air gap flux signal is generated by integrating the instantaneous voltage across a stator phase winding during the interval the current in that winding is zero. Pulsating torque is the product of the high pass filtered flux signal and the inverter input or dc link current.

Abstract: For use with an adjustable speed a-c electric motor having a stator adapted to be coupled to a source of variable frequency excitation and a rotor in which torque is developed when the motor is excited, the strength of said torque being dependent on interacting current and flux in the motor, a scheme is provided that comprises means for deriving an angle feedback signal representative of the actual phase angle between the aforesaid current and flux and means responsive to said angle feedback signal for controlling the source of variable frequency excitation so as to control the frequency of stator excitation as a function of the angle feedback signal.

Abstract: Improved stable four-quadrant operation of an induction motor supplied with variable amplitude and frequency stator line current by a motor controller with a constant current source converter is achieved by using several feedback control loops to control the slip frequency as well as the stator line current amplitude and frequency. Speed feedback is employed with optional control of rotor speed. Motor performance is optimized by indirectly regulating air gap flux to its rated value by controlling slip frequency as a function of sensed stator current. Thus, torque is approximately linear with stator current.

Abstract: A motor control circuit and method for regulating the torque of an ac induction motor operated at a variable frequency utilizes as a controlled variable the modified in-phase component of stator current which is compensated for the voltage drop across the stator resistance. Both positive and negative torque are approximately linear assuming the slip frequency is changed linearly, and only the per phase line current and voltage are sensed. A traction application is described.