A motor drive device includes an inverter to apply power to a motor, and a plurality of relays to switch a connection state of the motor by each switching its state between a first state and a second state. A timing at which at least one of the plurality of relays switches from the first state to the second state is different from a timing at which the other relays switch from the first state to the second state.

A driving device includes a connection switching unit to switch a connection state of coils between a first connection state and a second connection state in which a line voltage is lower than in the first connection state, a controller to control a motor and the connection switching unit, and a rotation speed detector to detect a rotation speed of the motor. When the connection state of the coils is the first connection state and the rotation speed detected by the rotation speed detector becomes higher than or equal to a first rotation speed, the controller causes the motor to rotate at a second rotation speed higher than the first rotation speed, and then causes the connection switching unit to switch the connection state of the coils from the first connection state to the second connection state.

A drive apparatus for an electric motor includes an inverter, an inverter substrate, a wire connection switching unit, a control unit, and an alternating-current wire electrically connected at one end to the inverter and at the other end to one end of the windings of an electric motor. The drive apparatus for an electric motor includes an alternating-current wire electrically connected at one end to the alternating-current wires and electrically connected at the other end to one end of the wire connection switching unit, and an alternating-current wire electrically connected at one end to the other end of the wire connection switching unit and electrically connected at the other end to the other end of the windings of the electric motor. The drive apparatus for an electric motor includes a noise suppression unit provided at least on the alternating-current wires to suppress noise that occurs in the alternating-current wire.

An emergency power supply system for providing hydraulic power and electric power in an aircraft includes a fuel cell having an electric outlet for providing electric power, a conversion unit couplable with at least one of an AC bus and a DC bus and the electric outlet, and at least one hydraulic pump having a reconfigurable electric motor and a motor control unit and being couplable with a hydraulic system for providing hydraulic power. The conversion unit is adapted for converting a supply voltage of the electrical outlet to at least one of an AC voltage matching a predetermined voltage at the AC bus and a DC voltage matching a predetermined voltage at the DC bus. The reconfigurable electric motor is couplable with the fuel cell and the AC bus and is adapted for being operated by the supply of electric power either from the fuel cell or the AC bus.

A driving device includes a connection switching unit that switches connection condition of a coil between Y connection and delta connection, an inverter, and a control device that controls a carrier frequency of the inverter. The carrier frequency is set at a first carrier frequency when the connection condition of the coil is the Y connection. The carrier frequency is set at a second carrier frequency when the connection condition of the coil is the delta connection.

An air-conditioning apparatus including a compressor incorporating an electric motor; a temperature sensor configured to detect indoor temperature; a drive circuit configured to drive the electric motor; a connection switching device configured to switch connection of stator windings of the electric motor between a first connection state and a second connection state higher in line-to-line voltage than the first connection state; and a controller configured to enter thermo-off when the indoor temperature reaches a target temperature or a correction temperature set based on the target temperature and cause the connection switching device to switch connection, the thermo-off being entered by stopping the compressor via the drive circuit. When a thermo-off count reaches a reference count with the electric motor being in the first connection state, the controller causes the connection switching device to switch connection from the first connection state to the second connection state.

A motor drive system can detect a misconnection. A motor drive system for driving a motor including a plurality of stator windings includes: an inverter that converts a DC voltage supplied from a DC voltage source into an AC voltage and applies the AC voltage to the motor; a connection switching device that is disposed between the inverter and the motor and can switch a connection state of the stator windings; and a controller that performs abnormality determination on a connection state of the connection switching device on the basis of a current value of a current flowing in each of the stator windings.

An electric-motor driving device includes an inverter connected to terminals connected to windings of an electric motor including the windings, the inverter applying an alternating-current voltage to the electric motor, a switching unit connected to the terminals and capable of switching a connection state between the terminals, a detecting unit that detects at least one of a voltage and an electric current of the inverter, and a control unit that determines on the basis of a detection value detected by the detecting unit that an abnormality occurs in the switching unit and controls the inverter to short-circuit at least two of the terminals.

A driving device includes an inverter to output a voltage to coils, a connection switching unit to switch a connection state of the coils between a Y connection and a delta connection, and a controller. The controller causes the inverter to stop outputting, when the connection state of the coils is the Y connection and a current value of the inverter reaches a first threshold A, or when the connection state of the coils is the delta connection and the current value of the inverter reaches a second threshold B. The first threshold A and the second threshold B satisfy B<3A.

A vehicle includes an electric machine having independently selectable delta and wye windings. The electric machine has a lower torque producing limit with one of the windings than an other of the windings at a given speed. The vehicle includes a controller configured to select the other of the windings such that torque of the electric machine increases without increasing the given speed. The selection is responsive to operating with the one of the windings and a torque demand greater than the lower torque producing limit.