Abstract: A drive system (1) drives a multi-phase AC motor (2) having a plurality of windings. The drive system (1) includes a first power converter (3U), a second power converter (3V), a first conversion controller (20U), and a second conversion controller (20V). The first power converter (3U) causes a current to flow through a winding of a first phase of the multi-phase AC motor (2). The second power converter (3V) causes a current to flow through a winding of a second phase of the multi-phase AC motor (2). The first conversion controller (20U) decides on either a three-level phase voltage waveform or a five-level phase voltage waveform on the basis of setting information for designating a type of phase voltage waveform and controls the first power converter (3U) so that the decided phase voltage waveform is output from the first power converter (3U).

Abstract: Power conversion equipment which can detect a short circuit failure of series connected smoothing capacitors is provided. The equipment includes a capacitor failure detecting circuit having switch units, exciting resistors, contact resistors, and diodes. A switch unit is provided with an exciting circuit and a contact circuit, and when a predetermined current flows through the exciting circuit, the contact circuit is closed. The exciting circuit and an exciting resistor are alternately connected in series, and the contact circuit and a contact resistor are alternately connected in series. These serially-connected circuits are connected in parallel with each capacitor. When excitation of a switch circuit having a lowest potential is turned OFF, it is judged that one or more of the series connected capacitors has failed via a short circuit.

Abstract: To provide a power conversion equipment which can detect short circuit failure of series connected capacitors of a smoothing capacitor circuit 4. A capacitor failure detecting circuit is composed of the combination of switch units 7SW, exciting resistors 8R, contact resistors 9R, and diodes 10D. The switch unit 7SW is provided with an exciting circuit and a contact circuit, and when a predetermined current flows through the exciting circuit the contact circuit is closed. The exciting circuit of the switch unit 7SW and the exciting resistor 8R are alternately connected in series, and the contact circuit and the contact resistor 9R are alternately connected in series, corresponding to the number of the series connected capacitors, and these series circuits are connected in parallel with the capacitors.

Abstract: A signal pattern is generated to produce a current for driving a GCT thyristor. The current is produced by the use of a down converter. Also, a current limiter having an FET is used for protecting the down converter from being damaged by a negative voltage appearing at the gate of GCT when the GCT thyristor receives a reverse direction load current.

Abstract: A predetermined signal pattern is generated to produce current for driving the GCT thyristor. The current is produced by the use of a down converter. Also, a current limiter having an FET is used for protecting the down converter from being damaged by a negative voltage appearing at the gate of GCT when the GCT thyristor receives reverse direction load current.