Abstract: A diagnosing apparatus for diagnosing a dynamic system by detecting a fault of the dynamic system. The diagnosing apparatus comprises: disturbance estimating means for estimating an integrated disturbance vector, which is the sum of external and internal disturbance vectors of the dynamic system, based on an internal state vector of the dynamic system; correlation calculating means for calculating a cross-correlation between the estimated integrated disturbance vector and the internal state vector and for separating from the integrated disturbance a component relating to the internal disturbance; and diagnosing means for specifying a corresponding fault portion of the dynamic system from the separated component relating to the internal disturbance.

Abstract: A method of controlling current of a multi-phase inverter is based on the principle that, when an appropriate switching mode is set, the direction of change of the position of the end of the current deviation vector must converge within a specific range which is determined in accordance with a presently output voltage vector. Accordingly, the direction of change of the position of the end of the current deviation vector and a presently set switching mode are detected during each control period to make a judgement as to whether or not the detected current deviation change direction belongs to a predetermined reference change direction range.

Abstract: An inverter current controlling method wherein output currents of an inverter having a plurality of switching elements and connected to a three-phase load are detected, and the switching elements are ON/OFF controlled so that the waveforms of the output currents are approximated to set output current wave commands, respectively, comprising: maintaining a specific switching element in a specific state so that a specific output terminal of the inverter is fixed to a specific polarity during a period of time when a specific ideal phase voltage of the three-phase load corresponding to the output current wave command is in a predetermined phase; and ON/OFF controlling the switching elements other than the specific switching element during the period of the predetermined phase so that the output current waveforms are approximated to the output current wave commands, respectively. Also disclosed is an inverter current controlling apparatus suitably employed in the above-mentioned method.

Abstract: The multi-level inverter according to the present invention comprises: a group of DC power supplies including three or more DC power supplies which are connected in series with same polarities, a group of terminals including a plurality of terminals for taking desired voltage levels from the opposite end and respective connecting points of group of DC power supplies, a group of switches consisting of switches having open modes and short-circuit modes equal in number to the terminals in the group of the terminals, with respective terminals on the input side being connected to the terminals in the group of terminals and respective terminals on the output side being commonly interconnected, and output terminals connected to the terminals on the output side being commonly interconnected in the group of switches. A contact of a switch connected to a terminal corresponding to desired voltage levels is closed to output voltages at multi-levels to be applied to a load.

Abstract: A method of controlling electromagnetic casting for carrying out the pouring of molten metal is disclosed which utilizes an electromagnetic force generated by a travelling magnetic field. The apparatus for performing the method is constructed so that a single magnet coil for generating a travelling magnetic field is employed and the input current of one phase of the three-phase alternating current to be applied to the magnet coil is subjected to phase control, whereby the electromagnetic force of the travelling magnetic field is controlled so as to automatically effect compensation for the change of the molten metal level due to the decrease of the amount of molten metal remaining to be poured.