METHOD OF CONTROL OF THREE-PHASE VOLTAGE INVERTER FROM BUSBARS AND DEVICE REQUIRED TO REALIZE IT Russian patent published in 1997 - IPC

FIELD: electrical engineering. SUBSTANCE: inputs 30 and 31 of speed controller 8 are supplied with signals proportional to preset torque on shaft of induction motor 3 and to its rotor rotational speed, respectively. Sinusoidal sequences proportional to preset values of phase currents of motor 3 are formed at outputs 32 and 33 of controller 8, and phase pulse signals a,b,c of the same frequency are generated at outputs 46,47,48 of controller 8. Error amplifiers 9,10, 11 compare preset and actual values of phase currents of motor 3, and comparators 12, 13, 14 determine sign of difference between preset and actual values of currents. Signals Xa, Xb, Xc which control thyristor 24-29 of inverter 1 are formed in permanent storage 45 by the given algorithm from combination of signals a, b, c and ya, yb, yc which determine the sign of difference between preset and actual currents. This makes it possible to follow current form in each phase of motor at 1/6 part of period, twice per period and thus to improve efficiency of inverter. EFFECT: reduced losses of inverter, minimized effect of restriction by minimum realized phase current and consequently by minimum torque; this can be obtained by decreasing the frequency of change-over of rectifier valves. 2 cl, 5 dwg