Inverter apparatus

An inverter apparatus comprising:

• an inverter that converts a direct-current voltage input via a direct-current bus into three phase alternating voltages and outputs the three phase alternating voltages to a motor;
• an inverter control unit that controls the inverter;
• and
• a current detection unit that detects the direct current flowing in the direct-current bus,
• wherein the inverter control unit includes a first current calculation section that holds, in advance, a γ-axis current arithmetic expression including the direct current as a parameter, and calculates a γ-axis current using the direct current detected by the current detection unit for the γ-axis current arithmetic expression,
• wherein the inverter control unit comprises a second current calculation section that calculates three phase alternating currents from the direct current detected by the current detection unit and calculates a δ-axis current from the three phase alternating currents,
• wherein the inverter control unit comprises a V/f control section to which the γ-axis current calculated by the first current calculation section and the δ-axis current calculated by the second current calculation section are input;
• and
• wherein the V/f control section comprises
• a power supply frequency command calculation section that calculates a power supply frequency command using the γ-axis current and a speed command for the motor,
• a γ-axis voltage command calculation section that calculates a γ-axis voltage command using an arithmetic expression including an integral term of the δ-axis current and the power supply frequency command as parameters, and
• a δ-axis voltage command calculation section that calculates a δ-axis voltage command using a linear function of the δ-axis current.