Method and apparatus for operating a field-oriented rotating-field

Abstract

In the field-oriented control of an asynchronous machine, the flux angle of which is calculated by a flux computer from the current and the voltage as the integral of the EMF, the correct flux vector must be available already at the start-up of the machine. For this purpose, one axis (M.phi.1) of a model coordinate system as well as the components (iO*, iM*=0), referred to the model coordinate system, of a vector parallel to this axis is determined at an input device (E1, E2) by a constant, given starting angle (.phi.MO*). This vector is transformed by means of the field angle (.phi.s) calculated by the flux computer for forming the converter control variables into the stator coordinate system while the machine is excited but standing still. The angle deviation (.phi.MO*-.phi.s) of the calculated field angle from the starting angle is used by a controller (CR) for correcting the calculated field angle. Before the setting device switches to the operationally provided reference value transmitter (RV), the calculated filed angle (.phi.s) therefore assumes the starting angle (.phi.MO*) and the control device forces via the converter a stator current and machine flux parallel thereto. At the same time, also the parameter of the stator resistance used for calculating the flux can be adjusted.