| Abstract |
A.C. machines in traction applications are normally saturated during voltage controlled operation. Some calculations, which are based on a simple model describing the saturated a.c. machine, indicate possibilities to calculate the stator flux without speed measurement even at stator frequency zero. The new method detects changes of the differential inductances estimated from stator voltages and stator currents. These changes of the differential inductances result from saturation effects. The saturation effects and the stator flux space vector are linked. Therefore a signal processor may be used to calculate the stator flux space vector based on measured quantities of stator voltages and stator currents without any speed measuring device, even at stator frequency zero. Knowing the stator flux and stator current space vectors is sufficient for a fast-response control of torque and flux even of high-performance a.c. drives at all stator frequencies. |
