Inverter control apparatus and motor drive system

A motor drive system comprising:

• a synchronous motor;
• an inverter main circuit that drives the synchronous motor;
• an electric-current detector that detects an electric current flowing between the inverter main circuit and the synchronous motor;
• a command generator that generates an electric-current command value of an output electric current that is output from the inverter main circuit to the synchronous motor, in accordance with a torque command that is supplied externally;
• and
• an electric-current controller that generates a voltage command value for the inverter main circuit so that the electric-current command value and a detected electric-current value that is detected in the electric-current detector are equal to each other, wherein
• the command generator comprises a limiting unit that sets, when an absolute value of the electric-current command value is smaller than a lower limit value, the absolute value of the electric-current command value to a value which is equal to the lower limit value, and generates the electric-current command value so that a fundamental wave current, an absolute value of an amplitude of which is equal to or greater than the lower limit, is supplied to the synchronous motor to saturate a rotor bridge unit of the synchronous motor magnetically, in driving the inverter main circuit.