Patent ID: 8035330
Filing Date: 2011-10-11
Classification: H02P

Abstract:
1. A synchronous motor drive apparatus comprising: a three-phase inverter that supplies three-phase AC power to a synchronous motor, the voltage and frequency of the AC power being variable; at least one position sensor that outputs a position sensor signal related to a voltage induced in each of the windings of the synchronous motor; a current phase detection unit that detects the phase of the current flowing through a winding of the synchronous motor; a motor speed calculation unit that calculates a rotational speed of the synchronous motor; a speed control unit that outputs a first voltage adjusting component to cause the rotational speed of the motor to approach a speed command value for the motor; a phase control unit that outputs a second voltage adjusting component to cause the phase difference between the phase of the position sensor signal and the phase of the current flowing through the winding of the synchronous motor to approach a phase difference target value; and a voltage determination unit that determines an amplitude and a phase of the output voltage of the three-phase inverter depending on the first and second voltage adjusting components, wherein the three-phase inverter is so controlled as to generate the output voltage having amplitude and phase determined by the voltage determination unit; wherein the current phase detection unit further includes a current polarity detection circuit that detects a polarity of the current of the winding, and that outputs a current polarity signal indicating the polarity of the current of the winding; and wherein the phase control unit further includes a phase difference target value setting section that sets a phase difference target value, and performs a control operation such that the phase difference between the current polarity signal and the position sensor signal approaches the phase difference target value.