Abstract: In a power converting apparatus including a capacitor connected in series which serves to divide a DC voltage, and a PWM inverter bridge for converting the DC voltage into an AC phase voltage having three electric potentials of a positive voltage, a negative voltage and an intermediate voltage in a plurality of phases, a zero voltage period generator (11) is switched by signal switching devices (5 to 10) when a load current reaches a first overcurrent level based on the detection of an overcurrent detector (12), and there is provided a zero voltage period having an intermediate voltage in which output phase voltages having all phases of the power converting apparatus become the intermediate voltages, thereby carrying out a current limitation. With an inexpensive structure, consequently, a rapidly increased current in an inverter can be instantaneously suppressed at time of the detection of an overcurrent.

Abstract: A D.C. reactor has a core structure having two opposed cores separated by a magnetic gap, to form a closed magnetic circuit. A coil is wound on one or both of the cores. A pair of permanent magnets for biasing are disposed on the core structure. The bias flux generated by the permanent magnets and the flux generated by the coil to flow in opposite directions. Bypass means for causing the bias flux generated by the permanent magnets to bypass the magnetic gap are provided. In an embodiment the core structure comprises an E-shape core and an I-shaped core, the magnetic gap is defined between a center leg of the E-shaped core and the I-shaped core, the coil is wound on the center leg of the E-shaped core, and each permanent magnet is shaped as a rectangle and disposed on both side surfaces of the center leg of the E-shaped core.

Abstract: An inverter driving method for has an arrangement polyphase induction motor, for altering a plurality of winding connections of the motor and a storage arrangement for a plurality of motor control constant groups preset corresponding to the respective winding connections so as to perform optimal vector control. When the classification of the winding connection is selected, one set of motor control constant groups corresponding to the winding connection is read out of the storage arrangement and applied to a control unit of the induction motor as control constants.