Control device of ac motor

A control device of a three-phase alternate current motor comprising:

• an inverter having a plurality of switching elements for driving the alternate current motor;
• at least one current sensor, which senses a current flowing in a respective phase among three phases of the alternate current motor at a given sampling timing;
• and
• a control means that switches on and off each switching element by feeding back a plurality of dq axis current calculated values, which are obtained by dq transforming a plurality of phase current sensed values in two or more phases sensed by a plurality of current sensors, or obtained by dq transforming a phase current sensed value of one phase and a current estimated value of other phase estimated from the phase current sensed value of the one phase, to a plurality of dq axis current command values, or by feeding back a torque estimated value, which is estimated based on the dq axis current calculated values, to a torque command value, so that the control means controls the current passing through the alternate current motor,
• wherein the control means includes at least one first order current operation part that:
• expands a phase current sensed value of one phase in Fourier series as a function of an electric angle;
• extracts a first order component of the Fourier series;
• and operates a first order current operated value of the one phase,
• wherein the at least one first order current operation part integrates a calculated value based on the phase current sensed value of the one phase at an integral angle for k periods of the electric angle so that Fourier coefficients are calculated,
• wherein the integral angle is set by dividing the k periods of the electric angle by N, and
• wherein k represents a natural number, and N represents another natural number.