A heat pump device includes a compressor compressing refrigerant; a motor driving the compressor; an inverter applying alternating-current voltage to the motor; and an inverter control unit generating a control signal for controlling the inverter. The inverter control unit executes control by using a first switching pattern in which all of three switching elements on a positive or negative voltage side of the inverter are changed to an ON state, then executes control by using a second switching pattern in which two switching elements to which electric current flows in the same direction when controlled by using the first switching pattern are changed to an OFF state, and then executes control by using a third switching pattern in which two switching elements on a reverse voltage side of the two switching elements changed to an OFF state by using the second switching pattern are changed to an ON state.

A multi-stage compression refrigeration cycle device includes a controller that controls rotational speeds of a low-stage side compression mechanism and a high-stage side compression mechanism, and a physical quantity sensor that detects a physical quantity correlated with a pressure of a low-pressure refrigerant. The controller is configured to increase a rotational speed ratio of the rotational speed of the low-stage side compression mechanism to the rotational speed of the high-stage side compression mechanism as the pressure of the low-pressure refrigerant becomes higher, based on the physical amount detected by the physical quantity sensor.

The present disclosure relates to an adaptive logic board that includes a signal sensing circuit configured to receive an input signal as an electrical current. The signal sensing circuit includes a plurality of resistors and a plurality of switches configured to electrically couple or electrically decouple the plurality of resistors from the signal sensing circuit, in which each switch of the plurality of switches corresponds to a corresponding resistor of the plurality of resistors. The adaptive logic board also includes a sensing unit that is configured to measure a voltage drop of the input signal across an active resistor of the plurality of resistors.

CPU of an air conditioner reads out a heat exchanger outlet temperature stored in time series into a memory part to check whether the current heat exchanger outlet temperature is a second threshold temperature or lower or not, whether the drop rate of the heat exchanger outlet temperature calculated using the latest heat exchanger outlet temperature and the second-to-the-latest heat exchanger outlet temperature is a specific drop rate or higher or not, and whether the number of indoor units in operation of indoor units has increased or not during calculation of the drop rate of the heat exchanger outlet temperature. And, when the second frost forming condition is satisfied, CPU switches a four-way valve to set a refrigerant circuit into a cooling cycle to thereby execute a defrosting operation preparation processing and, on completing the defrosting operation preparation processing, resumes a compressor to start a defrosting operation.

A compressor includes: a motor that includes a rotor including opposed magnets; a compression unit that compresses a refrigerant; and a crankshaft that is connected to the motor and the compression unit and is configured to transmit rotational driving of the motor to the compression unit, wherein the magnets are arranged such that the difference in magnetic force between the opposed magnets eliminates a force that deflects the crankshaft when the motor is rotationally driven.

An air-conditioning apparatus including a refrigeration cycle configured by connecting one or more load-side units including a load-side heat exchanger and a load-side expansion device with a heat-source-side unit including a heat-source-side heat exchanger and a compressor and by causing refrigerant to circulate through a refrigerant circuit including the load-side heat exchanger, the load-side expansion device, the heat-source-side heat exchanger, and the compressor, controls, during a heating operation, the opening degree of the load-side expansion device, based on the discharge pressure of the compressor, so that the pressure of refrigerant at the outlet of the compressor becomes equal to a target pressure, in the case where the operation capacity of the compressor is approximately at the maximum value of the operation capacity of the compressor.

A power converter including a compressor as a load includes a compensation current output (80) allowing compensation current (Ic), which compensates for leakage current (Ia), to flow. A controller (50) receives a detection signal from a rotational speed sensor (55) which senses the rotational speed of the compressor (CM). When the rotational speed has increased to a set rotational speed at which the leakage current (Ia) is lower than or equal to its limiting value (Lmax) (e.g., the limiting value specified under the Electrical Appliances and Materials Safety Act or by the IEC) in a state where the compensation current output (80) is off, the compensation current output (80) is switched from an on state to an off state. This may reduce the leakage current from the compressor with low power loss.

An air-conditioning apparatus can suppress occurrence of disproportionation (an autolytic reaction) when HFO1123 refrigerant or a refrigerant mixture containing HFO1123 is applied. The air-conditioning apparatus includes a controller controlling at least one of an operation frequency of a compressor, an opening degree of an expansion valve, and an air amount of a fan sending air to a heat-source-side heat exchanger so that a temperature and a pressure of the refrigerant discharged from the compressor do not exceed threshold values.

A simple inverter-controlled refrigerator includes temperature detector (17), constant speed main body control unit (12) whose power is turned on/off by temperature detector (17), and that can drive a constant speed compressor, inverter control unit (14) that is connected to constant speed main body control unit (12), and that is operated, based on a power on/off signal of constant speed main body control unit (12). And variable speed compressor (8) that is connected to inverter control unit (14), and that is controlled, based on an output from inverter control unit (14). Inverter control unit (14) has rotation speed setting unit (23) which is operated, based on the power on/off signal of constant speed main body control unit (12), and which is configured to set a rotation speed of variable speed compressor (8), and inverter drive circuit unit (24) which drives variable speed compressor (8) at the rotation speed set by rotation speed setting unit (23).

An inverter control device includes an inverter main circuit, a current detector, a voltage detector that detects a DC voltage between DC bus lines, and an inverter control unit that generates PWM signals to perform on/off control of a plurality of semiconductor switching elements respectively with a DC current and a DC voltage. The unit sets a carrier period of PWM signals to be 1/N times a calculation period in which the PWM signals are generated, performs detection of a DC current detected by the current detector in a 1/2 calculation period immediately before a calculation start timing for generating PWM signals, calculates an output voltage vector based on the detected DC current, and reflects PWM signals generated from the output voltage vector in one calculation period from a 1/2 calculation period after the calculation start timing to 3/2 control calculation periods after the same.