Abstract: A three-level power conversion apparatus can suppress fluctuation in a neutral point voltage even when operated as a reactive power regulator. The three-level power conversion apparatus is composed of first and second three-level converters connected to an AC power supply, positive side and negative side DC capacitors, a three-level inverter to drive an AC motor, and converter control unit for controlling the three-level converters. The converter control unit has first and second reactive current controllers for controlling so that reactive portions of input currents of each three-level converter become a prescribed reactive current reference, first and second neutral point voltage fluctuation suppressing units for controlling a PWM controller, to make a voltage difference of two DC capacitors zero, and an active current controller for supplying a prescribed circulating active current from one three-level converter to other three-level converter.

Abstract: To provide a three-level power conversion apparatus which can suppress fluctuation in a neutral point voltage even when operated as a reactive power regulator. The three-level power conversion apparatus is composed of first and second three-level converters 2A, 2B connected to an AC power supply system, positive side and negative side DC capacitors 3P, 3N, a three-level inverter 4 to drive an AC motor 5, and converter control means 10 for controlling the three-level converters 2A, 2B.

Abstract: There is provided a driving apparatus of an electric motor for a reduction roll that can improve maximization of rolling performance and a speed decrease amount by making maximal use of torque that various electric motors can generate during material entry.

Abstract: There is provided a driving apparatus of an electric motor for a reduction roll that can improve maximization of rolling performance and a speed decrease amount by making maximal use of torque that various electric motors can generate during material entry.