초록 ▼

A first PWM inverter for converting the ac voltage of an ac power source to a dc voltage is connected through a dc circuit with a second PWM inverter for driving an ac motor. A smoothing capacitor is provided in the dc circuit. The firing angles of the first inverter are so controlled that the volta

A first PWM inverter for converting the ac voltage of an ac power source to a dc voltage is connected through a dc circuit with a second PWM inverter for driving an ac motor. A smoothing capacitor is provided in the dc circuit. The firing angles of the first inverter are so controlled that the voltage in the dc circuit may be kept at a predetermined value and the second inverter is controlled in accordance with the speed instruction signal for the ac motor, whereby the ac motor can operate a regenerative operation without inducing higher harmonic components.

대표청구항 ▼

An apparatus for controlling an ac motor, comprising: (a) a first PWM inverter for converting an ac voltage from an ac power supply to a dc voltage; (b) a second PWM inverter for inverting the dc voltage output of said first inverter to an ac voltage which is variable in amplitude and frequency; (c)

An apparatus for controlling an ac motor, comprising: (a) a first PWM inverter for converting an ac voltage from an ac power supply to a dc voltage; (b) a second PWM inverter for inverting the dc voltage output of said first inverter to an ac voltage which is variable in amplitude and frequency; (c) an ac motor driven by said second inverter; (d) a capacitor connected between dc circuits connecting said first inverter to said second inverter; (e) frequency control means for controlling the ignition of said second inverter in accordance with a frequency instruction signal; (f) power detector means for detecting an available power and a reactive power from said ac power supply; (g) means for setting an amplitude of the reactive power at a point of detecting a power output from said ac power supply to a predetermined value; (h) means for setting an amplitude of the voltage output of said dc circuits to a predetermined value; (i) means for detecting the voltage output of said dc circuts; (j) power control means for executing the ignition control of said first inverter, said ignition control including the steps of adjusting an input ac voltage component of said first inverter, which has a phase difference of 90°with respect to that of the output voltage of said ac power in accordance with a deviation between an instruction value and an actual value of said available power which correspond to a set value and an actual value of said dc circuit voltage, and also adjusting the input ac voltage component of said first inverter, which has the same phase as that of the output voltage of said ac power supply in accordance with a deviation between a set value and an actual value of said reactive power.