Patent ID: 7723945
Filing Date: 2010-05-25
Classification: H02P

Abstract:
1. A control device for a motor drive system including an inverter converting DC voltage into AC voltage for driving an AC motor, comprising: current detection means for detecting motor current supplied to said AC motor; rotational speed detection means for detecting a rotational speed of said AC motor; control method selection means for selectively setting a control method of voltage conversion in said inverter, depending on an operation condition of said AC motor; first motor control means for performing torque control based on said motor current detected by said current detection means, when said control method selection means selects a first control method in which an applied voltage to said AC motor is controlled according to a sinusoidal pulse width modulation method by vector control; second motor control means for performing torque control based on said motor current detected by said current detection means, when said control method selection means selects a second control method in which an application voltage to said AC motor is controlled according to a modulation method of outputting a voltage with a fundamental component larger than said sinusoidal pulse width modulation method; rotational speed change occurrence detection means for detecting that a rotational speed change of a prescribed value or greater occurs in said AC motor, during selection of said second control method, based on an output of said rotational speed detection means; and motor voltage correction means, when occurrence of a rotational speed change of said prescribed value or greater is detected by said rotational speed change occurrence detection means, for correcting the applied voltage to said AC motor by said second motor control means by a correction amount corresponding to a degree of said rotational speed change.