COMANDO DI UN INVERTITORE A SEQUENZA DI FASE PER UN MOTORE ASINCRONO ALIMENTATO CON CONVERTITORE DI FREQUENZA

In a circuit arrangement for controlling the frequency (f1) of a phase-sequence invertor (3), connected to an asynchronous machine (4), inside a converter having a DC intermediate circuit, the control frequency (f1) is formed in a summing element (14) by addition of a variable which is proportional to the rotation frequency (frot) and a variable which is proportional to the slip frequency (f2). The slip frequency (f2) is set via a voltage control loop. The latter consists of a first characteristic transmitter (20), which determines the basic value of the slip frequency as a function of the motor current and whose output variable is corrected by a voltage regulator (13). The reference variable (wE) for the voltage regulator (13) is produced by multiplication of a flux reference variable (w phi ) by the stator frequency (f1) of the asynchronous machine (4). The flux reference variable (w' phi ) is provided below the rated load point of the asynchronous machine (4) by a second characteristic transmitter (12), as a function of the machine current. Above the rated load point, this value is reduced by means of a field suppression circuit (22, 23, 24). The control variable (xE) for the voltage regulator (13) is provided by a computing circuit (10) which is connected downstream from measurement transducers (7, 8) for the terminal current and the terminal voltage. The circuit arrangement allows the frequency of the phase-sequence invertor (3) to be controlled in a simple manner for use of the asynchronous machine (4) ... Original abstract incomplete.