Motor control apparatus and method of controlling motor

Claim 1

In a synchronous motor that rotates a rotor through an interaction between a magnetic field occurring when multi-phase alternating currents are flown through windings and a magnetic field produced by permanent magnets, said multi-phase alternating current being generated by switching on and off a plurality of switching elements that are arranged in pairs for a plurality of phases and connected to a source and a drain of a power source, a motor control apparatus that controls operation of said synchronous motor by taking advantage of an electrical angle that defines position of said rotor, said motor control apparatus comprising: a voltage application unit including said plurality of switching elements, said switching elements switch on and off with a delay of a dead time, based on an estimated electrical angle, so as to apply a predetermined voltage to said windings; a controller that sends signals to said voltage application unit for providing the switching operation and applying a predetermined voltage corresponding to a torque command value, which is to be output by said synchronous motor, to said windings, said predetermined voltage includes the voltage which enables a significant electric current to flow through said windings, irrespective of magnitude of the voltage applied by said voltage application unit when the torque command value is substantially equal to zero; and an electrical angle correction unit that corrects the estimated electrical angle according to a predetermined arithmetic operation and specifies the corrected electrical angle as an estimated electrical angle at a next timing, said predetermined arithmetic operation using voltages corrected to eliminate an effect of the dead time, electric currents flowing through said windings in response to the voltages applied by said voltage application unit, and inductances specified according to characteristics of said synchronous motor.