Abstract: The invention provides a multi-level inverter control device that is capable of reducing loss of a switching element of a maximum current phase that occurs in an extremely low speed region or at zero frequency. The control device has a maximum current phase selector 52 configured to select a maximum current phase whose current amplitude is a maximum on the basis of current detected values or current command values of a three-phase N-level inverter (N is odd number of three or more); a subtractor 54U, 54V, 54W configured to subtract a voltage command value of a selected maximum current phase from each of the voltage command values of the three phases of the inverter; and a switching signal generator 55 configured to compare each of subtracted voltage command values of the three phases with the (N?1) carrier signals and generate a switching signal of each switching element of the inverter.

Abstract: The invention provides a multi-level inverter control device that is capable of reducing loss of a switching element of a maximum current phase that occurs in an extremely low speed region or at zero frequency. The control device has a maximum current phase selector 52 configured to select a maximum current phase whose current amplitude is a maximum on the basis of current detected values or current command values of a three-phase N-level inverter (N is odd number of three or more); a subtractor 54U, 54V, 54W configured to subtract a voltage command value of a selected maximum current phase from each of the voltage command values of the three phases of the inverter; and a switching signal generator 55 configured to compare each of subtracted voltage command values of the three phases with the (N?1) carrier signals and generate a switching signal of each switching element of the inverter.

Abstract: In an elevator speed control circuit that has a proportional and integral speed amp 3 responsive to the deviation between a speed command .omega.* and actual motor speed .omega..sub.M, there is provided a car motion feedback circuit that amplifies the difference between a speed command .omega.* and actual car speed .omega..sub.car (or acceleration command and actual acceleration) with amp 12, extracts car vibration characteristics through band-pass filter 14, and changes these vibration components to the optimal phase in a phase correction filter 16 for feeding back. A load torque predictor 21 estimates load torque from signals from circuits 2-19 and from actual motor speed .omega..sub.M to improve speed feedback characteristics and the effectiveness of external disturbance suppression in elevator speed control. A variety of variable circuit elements are disclosed.

Abstract: An inertia lowering control apparatus for a two-mass inertia system, the two-mass inertia system having a motor (induction motor), a load of the motor, and a flexible drive shaft having a low rigidity interconnected between the motor and load, is used to suppress an axially torsional vibration occurring on the flexible shaft in the two-mass inertia system. For example, the first-order lag filter having a transfer function as 1/(1+ST.sub.F) is added at an output portion of the Simulator Following Control section which serves as a disturbance suppression circuit together with a shaft torque estimating observer to estimate a shaft applied torque .tau..sub.S. A simulation of the above-described example indicated that even if the observer gain of the shaft torque estimating observer was relatively small, the effect of suppressing the axially torsional vibration was remarkable.