Motor driving apparatus and air conditioner

A motor driving apparatus comprising:

• an inverter to drive a first synchronous motor and a second synchronous motor each including a rotor;
• and
• a controller to control the inverter,
• wherein
• the controller pulls in the rotor of the first synchronous motor and the rotor of the second synchronous motor to a designated position by performing direct-current excitation prior to starting of the first synchronous motor and the second synchronous motor, and
• in performing the direct-current excitation, the controller
• determines, for each of the first and second synchronous motors, a d-axis current and a q-axis current corresponding to three-phase currents flowing through the synchronous motor,
• selects one of the d-axis currents of the first and second synchronous motors that is larger in absolute value than the other of the d-axis currents,
• selects one of the q-axis currents of the first and second synchronous motors that is larger in absolute value than the other of the q-axis currents,
• determines a d-axis voltage command value for making the selected d-axis current equal to a d-axis current command value,
• determines a q-axis voltage command value for making the selected q-axis current equal to a q-axis current command value,
• converts the d-axis voltage command value and the q-axis voltage command value to three-phase voltage command values, and
• controls the inverter to make output voltages of the inverter equal to the three-phase voltage command values.