Patent ID: 7224171

Claim:
An inverter output current detection method for an inverter, the inverter having an LC filter made up of a reactor and a capacitor at an output side of an inverter circuit and supplying a load with a terminal voltage of the capacitor as an output voltage vo, the detection method detecting as an output current a current io obtained by subtracting a capacitor current ic flowing through the capacitor from a reactor current iL flowing through the reactor, comprising the steps of: detecting the output voltage vo for obtaining its effective value or average value V; obtaining cosine wave digital data (cos WaveData) by advancing by 90 degrees a phase of an inverter sine wave data used to obtain the output voltage vo; and digitally calculating a current ic′ equivalent to the capacitor current ic by an expression shown below ic′=V×ω 0 ×C× [cos WaveData]× K where the ω0 is an angular frequency of the output voltage, the C is a capacitance of the capacitor, and the K is a value obtained by multiplying a detection ratio for detecting the output voltage vo, a conversion ratio for converting an analog value to a digital value and a conversion ratio for converting the effective value or average value V into a maximum value; using the current ic′ equivalent in place of the capacitor curent ic to determine the output current; and outputting the inverter output current.