Drive system for electric motor

A drive system for an electric motor, the system controlling drive of a rotating electric machine having windings for a plurality of phases, comprising:

• a first inverter that includes first switching elements and is connected to one end of each of the windings and a first voltage source;
• a second inverter that includes second switching elements and is connected to the other end of each of the windings and a second voltage source that is provided separately from the first voltage source;
• and
• a control unit that includes a first inverter control calculation section controlling an on-off operation of each of the first switching elements based on a first carrier wave and a first modulation wave and a second inverter control calculation section controlling an on-off operation of each of the second switching elements based on a second carrier wave and a second modulation wave,
• wherein when a sum of a voltage of the first voltage source and a voltage of the second voltage source is more than a voltage determination threshold, and torque of the rotating electric machine is smaller than a torque determination threshold, the control unit controls a modulation factor of the first modulation wave and a modulation factor of the second modulation wave to be different from each other.

A drive system for an electric motor, the system controlling drive of a rotating electric machine having windings for a plurality of phases, comprising:

• a first inverter that includes first switching elements and is connected to one end of each of the windings and a first voltage source;
• a second inverter that includes second switching elements and is connected to the other end of each of the windings and a second voltage source that is provided separately from the first voltage source;
• and
• a control unit that includes a first inverter control calculation section controlling an on-off operation of each of the first switching elements based on a first carrier wave and a first modulation wave and a second inverter control calculation section controlling an on-off operation of each of the second switching elements based on a second carrier wave and a second modulation wave,
• wherein when a sum of a voltage of the first voltage source and a voltage of the second voltage source is more than a voltage determination threshold, and torque of the rotating electric machine is smaller than a torque determination threshold, the control unit controls at least one of a frequency of the first carrier wave and a frequency of the second carrier wave to be smaller than in an ordinary time.