| Abstract |
A digital torque-computer, which calculates the shaft torque of current-source-inverter fed squirrel-cage induction motors, is presented, By using the method of power balance only the measurement of electrical quantities is required. Compared to commonly used techniques based on mechanical principles the digital method provides the advantages of simple installing, high reliability and negligible costs of maintenance. The induction power, which determines the electromagnetic torque is evaluated from the d.c.-link power using machine and d.c./a.c.-converter characteristics available from the manufacturer. In order to achieve high accuracy additional losses, which are only known exactly in its structure, are modeled with respect to the stator current. The unknown frequency-depending parameter-functions are determined by automatical calibration. |
