Abstract: A power converter comprises: a rectifier composed of a plurality of bridge-connected diodes; reactors each connected in series in each power line of the rectifier; a chopper circuit having two switching elements connected in series between two DC output terminals of the rectifier; star connection capacitors, each of one end thereof being connected to the power source side of each reactor and each of the other end thereof being connected in common to a mutual connection point of the two switching elements of the chopper circuit; a smoothing capacitor for smoothing an output voltage of the rectifier; and ring connection capacitors each connected between two power lines and further between the AC power source and each of the reactors.

Abstract: It is possible to accurately and easily detect an abnormality in an electronic expansion valve without cutting or separating an electronic expansion valve from a cooling medium circuit. When an excitation pulse current from a drive circuit is output, a magnet rotor of an electronic expansion valve rotates. A hall element detects the position change of the magnet rotor at this time as detection pulses. The number of the detection pulses at this time is sent to a first up-down counter via an amplifier and a rectifier and is counted. The number of excitation pulses is also counted by a second up-down counter. The abnormality detection element judges that there is normal operation when the two count numbers of the first and second counters are in agreement, and that there is an abnormality when the two are not in agreement.

Abstract: In a communication control system for transmission of a serial signal between a receiver controller with a microcomputer and a transmitter controller with a microcomputer, if an abnormal condition such as overrun of the receiver microcomputer occurs, or when necessary, a unit within the transmitter controller prevents transmission of control data signals for a predetermined period, and a unit within the receiver controller resets the receiver microcomputer after it has detected that control data signals from the transmitter controller have not been received for a predetermined period.

Abstract: A refrigeration cycle is a closed cycle constituted by a variable power compressor, a four-way valve, an indoor heat exchanger, an expansion valve and an outdoor heat exchanger. Air-conditioned air is supplied from the refrigeration cycle to a plurality of rooms to be subjected to air conditioning through a supply duct at a portion near a supply opening for supplying the air-conditioned air to a corresponding one of the rooms and controls a flow amount of the air-conditioned air supplied from the supply opening. Air is returned from each room to the refrigeration cycle through a return duct. The indoor heat exchanger of the refrigeration cycle has a temperature sensor for detecting the temperature of the indoor heat exchanger. A system controller controls a drive frequency of the variable power compressor of the refrigeration cycle in accordance with a difference between the temperature of the indoor heat exchanger detected by the temperature sensor and a preset temperature of the indoor heat exchanger.

Abstract: In a serial signal transmission system for transmitting data signals in a serial manner from a transmitting part to a receiving part of the system, both supplied power from a common power source, are provided a signal line extended between the two parts, a device for detecting the polarity of the power source voltage, a device for generating binary pulses in response to the output of the polarity detecting device, and a control element provided in the signal line. The control element is made conductive in accordance with the binary pulses constituting the data signals.

Abstract: An air conditioning system comprising an outdoor unit in which a compressor is driven by the power supplied from a variable-frequency power supply and a plurality of indoor units operatively connected to the outdoor unit. Each indoor unit has a circuit for generating a frequency signal to be applied to the variable frequency power supply of the outdoor unit in response to a set room temperature and a temperature detected. In response to the frequency signals transmitted from the indoor units, the control unit of the outdoor unit detects a maximum frequency, a minimum frequency and the number of operating indoor units and determines the operating frequency of the variable frequency power supply in response to the maximum and minimum frequencies and the number of operating indoor units.