Patent ID: 9172322
Filing Date: 2015-10-27
Classification: H02P

Abstract:
1. A control apparatus for an AC motor comprising: an inverter for driving a three-phase AC motor; a current sensor for detecting a current flowing in a sensor phase in only one of three phases of the AC motor; and a controller for controlling energization of the AC motor by switching turn-on/off of a plurality of switching elements of the inverter, the controller further switching a control scheme between a current feedback control scheme and a torque feedback control scheme in controlling energization of the AC motor, the current feedback control scheme feeding a current detection value in the sensor phase detected by the current sensor and a current estimation value based on the current detection value back to a current command value, and the torque feedback control scheme feeding a torque estimation value pertaining to driving of the AC motor back to a torque command value, wherein: the controller has a current estimating section for estimating a d-axis current estimation. value and a q-axis current estimation value based on the current detection value in the sensor phase, and calculates the torque estimation value based on the d-axis current estimation value and the q-axis current estimation value calculated by the current estimating section when the torque feedback control scheme is applied; the current estimation section calculates a sensor phase reference current phase as a current phase relative to the sensor phase based on an α-axis current and a β-axis current in a fixed coordinate system formed of an α-axis agreeing with the sensor phase and a β-axis orthogonal to the α-axis, calculates the current estimation value in a phase other than the sensor phase based on the sensor phase reference current phase and the current detection value in the sensor phase, and dq-converts the current detection value in the sensor phase and the current estimation value in the phase other than the sensor phase to estimate the d-axis current estimation value and the q-axis current estimation value; and the current estimation section calculates, with respect to calculation of the α-axis current and the β-axis current, the α-axis current based on the current detection value in the sensor phase and, at least when the torque feedback control scheme is applied, calculates the β-axis current based on a differential value of the α-axis current.