To realize an accurate measurement of load by detecting effective power consumption of an AC three-phase asynchronous motor based on the measurements of current and voltage and then comparing the effective power consumption with a reference output from an AC three-phase asynchronous motor for driving the nominal load of a carrying means determined by a computer.
The AC three-phase asynchronous motor 1 is connected through the phase leads 2a, 2b and 2c of the motor with AC three-phase networks L1, L2 and L3. An evaluation unit 5 measures effective power consumption of the motor 1 based on the measurements of voltage and current. Effective power consumption thus determined is reduced by an offset value determined by taking account of the idling loss of a litter comprising the magnetic hysteresis loss and the frictional loss of the rotor in the motor 1 and then corrected by the component of current heat loss of the stator winding of the motor. The evaluation unit 5 determines the instantaneous relative load of the litter based on a reference output and calculates the difference or the ratio between the measured effective power consumption and the reference output.
MUENZEBROCK ANTON DIPL ING
SCHROEDER EBERHARD DIPL ING
