Abstract: An air conditioner has a power conversion device including: a reactor having a first end and a second end, the first end being connected to an AC power supply; a rectifier circuit that is connected to the second end of the reactor and includes a diode and at least one or more switching elements, the rectifier circuit converting an AC voltage outputted from the AC power supply into a DC voltage; and a detection unit detecting a physical quantity indicating an operation state of the rectifier circuit. Switching is made between control for a current from the AC power supply to be applied to the diode or control for the current to be applied to the switching element in accordance with an operating mode of the air conditioner.

Abstract: An air conditioner includes a compressor to compress a refrigerant used in a refrigeration cycle, a converter to generate DC voltage, an inverter to generate three-phase AC voltage from the DC voltage, a motor to generate driving force to drive the compressor by using a plurality of coils to which the three-phase AC voltage is applied, a connection switching unit to switch connection states of the plurality of coils, and an outdoor control device to control the connection switching unit. The outdoor control device restricts the switching of the connection states when a switching count of the connection states exceeds a count threshold value.

Abstract: An outdoor unit includes a housing that includes a front panel having an outlet for an airflow, a back panel facing the front panel, a left side panel, a right side panel facing the left side panel, a bottom panel, and a top panel facing the bottom panel. The outdoor unit further includes a control substrate that is provided in the housing and provided with an electric component, an electric component box in which the control substrate is provided, and a heat dissipator that is provided between the top panel and the electric component box and dissipates heat generated by the electric component. A second region surrounded by the heat dissipator, the back panel, the front panel, the electric component box, and the top panel is formed on a windward side of the heat dissipator.

Abstract: A direct-current power supply device includes a reactor, a bridge circuit that converts alternating-current voltage output from an alternating-current power supply, which is connected to the reactor, into direct-current voltage, a capacitor that smoothes the output voltage of the bridge circuit, a current detector that detects a first current flowing as an alternating current between the alternating-current power supply and the bridge circuit, a current detector that detects a second current flowing as a direct current between the bridge circuit and the capacitor, an overcurrent determination unit that determines on the basis of a detected first current value whether or not the first current is an overcurrent, and an overcurrent determination unit that determines on the basis of a detected second current value whether or not the second current is an overcurrent.

Abstract: A motor driving device that is a device for driving a motor including stator windings, includes: a connection switching unit that includes relays as mechanical switches connected to the stator windings and excitation coils opening or closing the relays by being energized or non-energized with excitation current and switches connection condition of the stator windings to either of first connection condition (star connection) and second connection condition (delta connection) different from the first connection condition by opening or closing the relays; and an inverter that supplies AC drive voltages to the stator windings.

Abstract: A power converter includes: a converter that includes switching elements to convert alternating current (AC) power output from an AC power source into direct current (DC) power; a reactor disposed between the AC power source and the converter; a smoothing capacitor connected to both ends of a DC terminal of the converter; and detectors that detect a physical quantity representing an operational state of the converter. A bus voltage command value is issued that has zones respectively having different change rates during boost operation of the converter, where the change rates each represent how a bus voltage included in the physical quantity changes with a change in a magnitude of the load obtained from the physical quantity.

Abstract: A converter device includes: a power conversion circuit including a reactor and a switching element, rectifying a voltage of alternating-current power supplied from an alternating-current power supply to a direct-current voltage, and boosting and outputting the direct-current voltage; a current detector detecting a current flowing in the reactor; a filter circuit filtering a first signal detected by the current detector; and a control unit generating a control signal on the basis of a carrier and a second signal generated by the filter circuit and controlling, on the basis of the control signal and with a first period, the switching element, the first period being a period of the carrier. The filter circuit cuts off a repetition frequency component in the first period and passes a repetition frequency component in a second period, the second period being longer than the first period.

Abstract: A power converter is configured to convert, into an AC voltage, a DC voltage supplied from a DC power supply connected between a first power supply wiring and a first ground wiring. A control device is connected between a second power supply wiring and a second ground wiring. The second power supply wiring is configured to supply a second power supply voltage lower than the first power supply voltage. The control device is configured to control the power converter. A separation device is configured to separate the first ground wiring and the second ground wiring from each other. The first ground wiring and the second ground wiring are electrically connected to each other at a single node.

Abstract: A power supply includes: a converter circuit including boost circuits, the converter circuit boosting a voltage output from a power source; a current detector that detects a first current flowing between the power source and the converter circuit; current detectors that each detect a second current, the second current being a sum current of currents flowing in switching elements of the boost circuits; and overcurrent determiners that determine whether the second currents are overcurrent on the basis of detection values of the second currents. When a result of the determination made by corresponding one of the overcurrent determiners indicates overcurrent, the boost circuits stop operating.

Abstract: A motor driving device that drives a motor with an alternating-current power converted from a direct-current power supply, includes an inverter that receives a pulse-width modulation signal and supplies the alternating-current power to the motor, and an inverter control unit that generates the pulse-width modulation signal and supplies the pulse-width modulation signal to the inverter. The inverter control unit reduces the number of pulses of the pulse-width modulation signal generated during a first period within one period of a mechanical angle of the motor to be lower than the number of pulses of the pulse-width modulation signal generated during a second period within the one period of the mechanical angle of the motor. The first period is a period during which a load torque is lower than a load torque during the second period.

Abstract: A direct-current power supply device includes a reactor, a bridge circuit that converts alternating-current voltage output from an alternating-current power supply, which is connected to the reactor, into direct-current voltage, a capacitor that smoothes the output voltage of the bridge circuit, a current detector that detects a first current flowing as an alternating current between the alternating-current power supply and the bridge circuit, a current detector that detects a second current flowing as a direct current between the bridge circuit and the capacitor, an overcurrent determination unit that determines on the basis of a detected first current value whether or not the first current is an overcurrent, and an overcurrent determination unit that determines on the basis of a detected second current value whether or not the second current is an overcurrent.

Abstract: An outdoor unit includes a housing that includes a front panel having an outlet for an airflow, a back panel facing the front panel, a left side panel, a right side panel facing the left side panel, a bottom panel, and a top panel facing the bottom panel. The outdoor unit further includes a control substrate that is provided in the housing and provided with an electric component, an electric component box in which the control substrate is provided, and a heat dissipator that is provided between the top panel and the electric component box and dissipates heat generated by the electric component. A second region surrounded by the heat dissipator, the back panel, the front panel, the electric component box, and the top panel is formed on a windward side of the heat dissipator.

Abstract: An outdoor unit includes: a housing; a compressor placed in the housing; a heat exchanger placed in the housing; and a blower placed in the housing, the blower admitting air from outside the housing and passing the air through the heat exchanger. Furthermore, the outdoor unit includes: a partition plate partitioning the housing into a compressor chamber and a blower chamber; a board on which an electronic component is mounted; a heat dissipator placed in the blower chamber and adjacent to the partition plate, the heat dissipator including a base and a plurality of fins, the base having a fin formation surface, the fins projecting from the fin formation surface, the heat dissipator dissipating heat of the electronic component; and a duct covering the heat dissipator. When the fins are viewed from the fin formation surface side, the fins extend toward the blower side from the partition plate side.

Abstract: A direct-current power supply apparatus includes: a reactor having one end connected to an alternating-current power supply; a bridge circuit, connected to an opposite end of the reactor, converting an alternating-current first voltage output from the alternating-current power supply into a direct-current voltage; and a current detector detecting an alternating current flowing between the alternating-current power supply and the bridge circuit. The reactor reduces an inductance in accordance with an increase of the alternating current and, when the alternating current exceeds a first current, has an inductance lower than one third of an inductance at which a current does not flow in the reactor. The bridge circuit performs an active operation when the detection value of the alternating current is larger than or equal to the first current and performs a passive operation when the detection value of the alternating current is lower than the first current.

Abstract: An outdoor unit includes a housing, a heat exchanger, an electric component box, a substrate, and a heat dissipator including multiple fins. The fins each have a first end situated in a windward side of an air passage formed between adjacent ones of the fins, and the first end faces the electric component box. When the heat dissipator and the electric component box are viewed from above, a first clearance gap having a first width and a second clearance gap having a second width greater than the first width are formed between the first end and the electric component box. The second clearance gap is situated closer to a back panel than the first clearance gap.

Abstract: A motor drive device includes a reactor, a converter circuit, a capacitor, an inverter circuit, and overcurrent determination units. The converter circuit converts a first AC voltage output from an AC power supply into a DC voltage. The capacitor smooths a second voltage on the DC side of the converter circuit. The inverter circuit converts DC power stored in the capacitor into AC power. One of the overcurrent determination units determines overcurrent based on a detected value of the first AC current, flowing between the AC power supply and the converter circuit. Another overcurrent determination unit determines overcurrent based on a detected value of the second DC current, flowing between the converter circuit and the capacitor. The converter and inverter circuits stop operating when the determination result of one of the overcurrent determination units indicates an overcurrent.

Abstract: A motor driver includes an inverter used for driving a motor and configured to apply an alternating-current voltage to the motor. The inverter drives, during start operation, a switching element of the inverter with a first PWM signal that is PWM modulated with a carrier frequency that is a first integer multiple of a frequency of the alternating-current voltage, and thereafter drives the switching element with a second PWM signal that is PWM modulated with a carrier frequency that is a second integer multiple of the frequency of the alternating-current voltage. The second integer is smaller than the first integer.

Abstract: A speed estimation apparatus for an AC motor includes a model deviation calculation unit, first and second angular velocity estimation units, and an adder. The deviation calculation unit calculates a model deviation based on a voltage, a current, and an estimated angular velocity of the motor. The first angular velocity estimation unit calculates a first estimated angular velocity as a low-frequency component including a DC component of a real angular velocity based on the model deviation. The second angular velocity estimation unit calculates a second estimated angular velocity as a high-frequency component of a real angular velocity based on a specific high-frequency component of the model deviation. The adder adds the first and second estimated angular velocities together. An addition value of the first and second estimated angular velocities is fed back as the estimated angular velocity to the deviation calculation unit.

Abstract: A power converting apparatus includes: a reactor that includes a first terminal and a second terminal, the first terminal being connected to an alternating-current power supply; a bridge circuit that is connected to the second terminal of the reactor, includes at least one or more switching elements, and converts an alternating-current voltage output from the alternating-current power supply into a direct-current voltage; a power-supply current detecting unit that detects a current from the alternating-current power supply; and a control unit that controls ON and OFF of the switching elements depending on a current value detected by the power-supply current detecting unit, in which two or more current thresholds for controlling ON and OFF of the switching elements are included.

Abstract: There are provided a booster to boost a voltage from a power supply, the booster including multiple stages connected in parallel; and a smoothing device to smooth the boosted voltage. Each of the multiple stages includes: an energy storage to receive current from the power supply and store energy; a switch to switch between connection and disconnection of a path for short-circuiting current from the energy storage; and a backflow preventer to prevent backflow from the smoothing device. At least one of the multiple stages is provided with a characteristic adjuster for adjusting switching characteristics of the switch.