Driving system of permanent magnet synchronous motor

摘要

When applying a high frequency voltage which alternates on positive and negative sides to a permanent magnet synchronous motor (103), a driving system of synchronous motor switches the applied voltage phase by 120 degrees successively and applies resultant voltages to three phases. A pulsating current generated by applying a high frequency voltage is detected at timing of elapse of a predetermined time At since an output voltage of at least one phase has changed from a state in which all output voltages of the three phases of a power converter are positive or negative. Current detection is conducted by using a DC resistor or a phase current sensor provided on a DC bus. A magnetic pole estimation unit (114) calculates the rotor magnetic pole position of the permanent magnet synchronous motor on the basis of differences between positive side and negative side change quantities in three-phase currents obtained from detected current values.