| Abstract |
Torque and flux measurements in ac motor are often a complicated matter.
For flux measurement, a coil or a field sensor must be inserted inside stator windings causing relevant
costs especially for big machines. Anyway, measurement has not great accuracy since calibration is
not easy. For torque measurement, a telemetry system can be installed on rotor axle but, especially for
notable accuracy, this system has high costs. Sometimes is not possible to install a telemetry directly
on rotor axle and a gear box must be interposed, losing every chance to obtain a precise measurement.
Cost and measurement uncertainties increase with machine size so that, for high power (more than 500
kW), this is about an insoluble matter.
In this paper, a method based on a state observer is proposed, that overcomes all disadvantages of
other methods because only voltages and current measurement is needed. For more accuracy, only
rotor speed measurement is needed in addition. |
