Patent ID: 9146166
Filing Date: 2015-09-29
Classification: G01L,H02P

Abstract:
1. A method for determining an electrical torque of an electrical machine having a rotor and a stator in a first high-rotation-speed range and in a second low-rotation-speed range, comprising: in the first high-rotation-speed range, measuring stator phase currents and stator phase voltages to determine therefrom a stator power and a stator frequency and computing with a defined number of pole pairs of the electrical machine a first electrical torque in the first high-rotation-speed range with a first algorithm; in the second low-rotation-speed range, determining an electrical rotor position angle from the defined number of pole pairs of the electrical machine and a mechanical rotor angle and computing stator flux components from the stator phase currents and the electrical rotor position angle, computing from the stator flux components a second electrical torque in the second low-rotation-speed range with a second algorithm which differs from the first algorithm, wherein an upper limit of the second low-rotation-speed range is slightly higher than a lower limit of the first high-rotation-speed range, defining a safe torque limiting function which limits a maximum permitted torque generated by the electrical machine in the second low-rotation-speed range, and reducing the torque in the second low-rotation-speed range so that the second electrical torque is smaller than the maximum permitted torque.