To provide a power converter in which a hard structure is not specified, an operating count of individual legs or unit inverters is averaged, heat concentration is eliminated, and a fault is disconnected for allowing a continuous operation at a failure and which has versatility, and a low failure rate.

The power converter comprises a plurality of leg groups 9 in which two more voltage levels can be outputted by on-off of each of a plurality of switching elements SA, SA-, SB and SB-, for converting DC power into polyphase AC powers of variable frequencies and variable voltages so that the leg groups 9 have the switching elements, and disconnecting means (11P, 11N, 12P, 12N and 14) for being disconnected from the groups 9 when an excess current flows to the element.