To provide a power converter which performs stable control though the total capacity of smoothing capacitor changes, depending upon the state of operation such as opening, etc., of a DC power source for plural units of inverters which differ in the capacity of smoothing capacitors as loads.

This device has a plurality of inverters 5 which are connected via switches 6 provided on the output side of converters 2 to these converters 2 for converting AC from an AC power source 1 into DC and convert the DC outputted from the converter 2 into AC having arbitrary frequency so as to drive an AC motor 8, a plurality of capacitors 4 and 7 which are provided between the converter 2 and the plural inverters 5 and within the inverters 5, respectively, and capacity measuring means of a capacitor 14 which measures the total capacity of the plural smoothing capacitors 4 and 7 by the current signals flowing in the smoothing capacitors 4 and 7, when the voltage is increaged to the specified value at a certain rate when preliminarily charging the smoothing capacitors 4 and 7 from the converter 2.