Patent ID: 7423395
Filing Date: 2008-09-09
Classification: H02P

Abstract:
1. A sensorless vector control method for an alternating-current motor, the sensorless vector control method employing: a power converter, for outputting arbitrary power to the alternating-current motor, a current detection circuit, for detecting a current supplied to the alternating-current motor, a coordinate conversion circuit, for converting the current supplied to the alternating-current motor into an exciting current detection value and a torque current detection value and for outputting thereof, an exciting current control circuit, for controlling an exciting current directional voltage so as to match the exciting current instruction value with the exciting current detection value, a torque current control circuit, for controlling a torque current directional voltage so as to match the toque current instruction value with the torque current detection value, a V/f conversion circuit, for calculating an induction voltage for the alternating-current motor based on a given output frequency instruction, a phase angle operation circuit, for obtaining a phase angle by integrating the given output frequency instruction, and an output voltage operation circuit, for calculating a level and a phase for an output voltage based on voltage instructions that are output by the exciting current control circuit, the torque current control circuit and the V/f conversion circuit, wherein a velocity detector and a voltage detector are not provided, a phase angle, output by the phase angle operation circuit, is added to the level and the phase output by the output voltage operation circuit in order to regulate the switching of the power converter, the sensorless vector control method comprising the steps of: applying a direct current or a direct-current voltage to the alternating-current motor in a free running state before the alternating-current motor is started, estimating a rotational direction and a velocity for the alternating-current motor based on a secondary current that flows at the application time, setting a frequency that corresponds to the rotational direction and the velocity for a frequency adjustment circuit to activate the alternating-current motor, matching the frequency adjustment circuit an output frequency with the velocity of the alternating-current motor, and estimating, based on the level of a current flowing in the alternating-current motor, that the rotational direction and the frequency designated for the frequency adjustment circuit deviate from the actual rotational direction and the actual velocity of the alternating-current motor.