To detect-capacitor deterioration by grasping capacity reduction of online capacitor without influence by a DC ripple voltage that varies greatly by load current and rotary frequency of an AC motor.
A power converter system comprises a converter 1 that generates a variable DC power supply from a commercial power supply 10, an inverter 2 that generates a variable frequency power from a variable DC power supply, and supplies the power to a motor 11, and a capacitor 3 connected to the variable DC power supply. Further a filter method 4 that inputs a carrier frequency component 22 of an inverter 2 and voltage between both capacitor- terminals and detects ripple voltage synchronized with a carrier frequency component 22, and a setting method 6 to set a value corresponding to a motor load current are installed. When peak-hold value 25 of the ripple voltage becomes more than value that set value 26 by a specified value, it is judged that capacitor capacity is deteriorated.
SUGIYAMA SHIGERU
AZUSAZAWA NOBORU
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