Bearingless motor system, compressor, and refrigeration apparatus

A bearingless motor system, comprising:

• a rotary shaft;
• a bearingless motor including
• a rotor provided on the rotary shaft, and
• a stator provided radially outside the rotor and including a shaft support winding and a motor winding;
• a first inverter configured to supply electric power to the shaft support winding to generate a shaft support force in order to support the rotary shaft in a non-contact manner;
• a second inverter configured to supply electric power to the motor winding to generate a rotational torque in the rotary shaft;
• and
• a control unit configured to control the first inverter and the second inverter,
• the control unit being configured to command at least one of the first inverter and the second inverter to output a voltage or a current on which a harmonic is superimposed in order to reduce a fluctuation in the shaft support force, the harmonic being obtained by multiplication of a rotational frequency of the bearingless motor by a natural number of two or more.