PROCESS CONTROLLING FREQUENCY ASYNCHRONOUS ELECTRIC DRIVE AND DEVICE FOR ITS IMPLEMENTATION Russian patent published in 1997 - IPC

FIELD: frequency-controlled electric drives of hoisting and ship mechanisms, pumps of various assignment. SUBSTANCE: controlling voltages of basic sequence with shift 2T₂/3, where T₂ is period of output voltage, controlling voltages of inverse sequence with indicated shift are formed in agreement with process controlling frequency asynchronous electric drive within frequency range from 0 up to f_net/2 of output voltage of eighteen-thyristor frequency converter with direct coupling. They are compared in each unipolar half-period of controlling voltage. In case of their equality one group of thyristors of frequency converter is rendered conducting under rectifier mode. In case of other polarity of half-period - under inverter mode within frequency range from f_net/2 to (f_net-f_rateds). With frequency f_net/2/2 shape of controlling voltages is changed to rectangular one, they are synchronized in phase with phases of angles of ON state of thyristors, frequency of controlling voltages is reduced to f_rateds, phases of asynchronous motor are connected to network cyclically with direct alternation of phases and with value of frequency of obtained voltages equal to f_rateds correspondence of network phases to phases of asynchronous motor is registered. EFFECT: increased stability of mechanical characteristics of motor which improves its electromechanical indices while f_net is network frequency and f_rateds is frequency of rated slip. 2 cl, 3 dwg