Abstract: A power conversion apparatus includes a rectifier circuit, an inverse conversion circuit, and a capacitor. The rectifier circuit rectifies alternating current power of the alternating current power supply. The inverse conversion circuit inversely converts a voltage Vdc rectified by the rectifier circuit into an alternating current voltage having a certain frequency and applies the alternating current voltage to a motor whose maximum power consumption Pmax is 2 kW or larger. The capacitor is provided between the rectifier circuit and the inverse conversion circuit and has a capacitance C that satisfies a condition of a following expression in relation to an alternating current voltage Vac of the alternating current power supply and the maximum power consumption Pmax. C ? 350 × 10 - 6 ? P ? ? max Vac 2 .

Abstract: A power conversion apparatus includes a rectifier circuit, an inverse conversion circuit, and a capacitor. The rectifier circuit rectifies alternating current power of the alternating current power supply. The inverse conversion circuit inversely converts a voltage Vdc rectified by the rectifier circuit into an alternating current voltage having a certain frequency and applies the alternating current voltage to a motor whose maximum power consumption Pmax is 2 kW or larger. The capacitor is provided between the rectifier circuit and the inverse conversion circuit and has a capacitance C that satisfies a condition of a following expression in relation to an alternating current voltage Vac of the alternating current power supply and the maximum power consumption Pmax. C ? 350 × 10 - 6 ? P ? ? max Vac 2 .

Abstract: An air conditioning system includes a microcomputer unit that controls a utilization-side unit and a heat source-side unit of an air conditioner and a thermostat connected to the air conditioner. The thermostat switches between an ON state in which the thermostat inputs a control signal to the microcomputer unit and an OFF state in which the thermostat does not input the control signal to the microcomputer unit. The system further includes a relay that switches to a feed state in which power is fed to the microcomputer unit or a non-feed state in which power is not fed to the microcomputer unit, and a power-on circuit within or externally attached to the air conditioner. The power-on circuit switches the relay from the power non-feed state to the power feed state using a voltage of the control signal inputted to the microcomputer unit.

Abstract: A device for controlling an air conditioner has a remote controller which receives an alternating current voltage from a secondary side of a first transformer, a full-wave rectifier connected to a secondary side of a second transformer, and a processor which receives a current rectified by the full-wave rectifier. One of output nodes of the full-wave rectifier is connected to one terminal of the secondary side of the first transformer. The remote controller has a switch connected to the secondary side of the first transformer, and transmits information that indicates a state of the switch to the processor as the amplitude of an AC voltage on a signal line connecting the remote controller and the processor together.

Abstract: An air conditioning system includes a microcomputer unit that controls a utilization-side unit and a heat source-side unit of an air conditioner and a thermostat connected to the air conditioner. The thermostat switches between an ON state in which the thermostat inputs a control signal to the microcomputer unit and an OFF state in which the thermostat does not input the control signal to the microcomputer unit. The system further includes a relay that switches to a feed state in which power is fed to the microcomputer unit or a non-feed state in which power is not fed to the microcomputer unit, and a power-on circuit within or externally attached to the air conditioner. The power-on circuit switches the relay from the power non-feed state to the power feed state using a voltage of the control signal inputted to the microcomputer unit.

Abstract: A device for controlling an air conditioner has a remote controller which receives an alternating current voltage from a secondary side of a first transformer, a full-wave rectifier connected to a secondary side of a second transformer, and a processor which receives a current rectified by the full-wave rectifier. One of output nodes of the full-wave rectifier is connected to one terminal of the secondary side of the first transformer. The remote controller has a switch connected to the secondary side of the first transformer, and transmits information that indicates a state of the switch to the processor as the amplitude of an AC voltage on a signal line connecting the remote controller and the processor together.