Abstract: In a refrigeration cycle apparatus according to the present disclosure, the circulation direction of refrigerant is switched between a first circulation direction and a second circulation direction opposite to the first circulation direction. The first circulation direction is a circulation direction in order of a compressor, a first heat exchanger, a first expansion valve, a third heat exchanger, a fourth heat exchanger, a second expansion valve, and a second heat exchanger. When a circulation direction of the refrigerant is the first circulation direction, the refrigerant from the third heat exchanger exchanges heat with the refrigerant from the second heat exchanger in the fourth heat exchanger. When a circulation direction of the refrigerant is the second circulation direction, the refrigerant from the fourth heat exchanger exchanges heat with the refrigerant from the first heat exchanger in the third heat exchanger.

Abstract: An adder adds a phase ?plus, which is n times a size of 60 degrees, to a phase output from a phase switching unit and outputs the phase as a voltage command phase ?. A voltage generation unit generates voltage command value based on the voltage command phase output by the adder and outputs the command value. A drive-signal generation unit, based on an output from the voltage generation unit generates drive signals corresponding to respective switching elements of an inverter, and outputs respective generated drive signals to the corresponding switching elements of the inverter, and generates a high-frequency AC voltage in the inverter.

Abstract: A selection unit switches between a phase ?p and a phase ?n different from the phase ?p substantially by 180 degrees, and outputs one of them in synchronization with a carrier signal. A voltage-command generation unit generates and outputs three-phase voltage command values Vu*, Vv* and Vw* based on the phase outputted by the selection unit. A PWM-signal generation unit generates three-phase voltage command values Vu*?, Vv*? and Vw*? by correcting the three-phase voltage command values Vu*, Vv* and Vw* outputted by the voltage-command generation unit according to a predetermined method, and generates six drive signals corresponding to switching elements of the inverter based on the three-phase voltage command values Vu*?, Vv*? and Vw*? and the carrier signal. The PWM-signal generation unit outputs the generated drive signals to the corresponding switching elements of the three-phase inverter, to cause the inverter to generate a high-frequency AC voltage.

Abstract: An air-conditioning apparatus, including a refrigerant circuit connecting a compressor, a heat source side heat exchanger, an expansion valve, and a use side heat exchanger in order with a refrigerant piping. A compressor heater is provided for heating the compressor when the compressor is not in operation. A compressor temperature sensor is provided for detecting a compressor temperature. A refrigerant temperature detection sensor is provided for detecting a refrigerant temperature in the compressor. A controller is configured to estimate an amount of liquid refrigerant in the compressor by integrating the temperature difference between the compressor temperature and the refrigerant temperature during a period in which the compressor temperature becomes lower than the refrigerant temperature, and control the heating operation, which is carried out by the compressor heater, on the basis of the estimated liquid refrigerant amount when the compressor is not in operation.

Abstract: While a compressor is stopped, a change rate of a refrigerant temperature per predetermined time is calculated on the basis of a value detected by a refrigerant temperature sensor, and a heating amount from a compressor heating unit to the compressor is made proportional to the change rate of the refrigerant temperature.

Abstract: When a compressor is in a stopped state and an outside air temperature change rate Tah exceeds zero, a first heating operation is started, and a heating capacity of a compressor heating portion is set in a range not more than a heating capacity upper limit Pmax based on the outside air temperature change rate Tah. A remaining refrigerant liquid amount Ms condensed in the compressor that had not been evaporated is acquired based on the outside air temperature change rate Tah and the heating capacity. If the outside air temperature change rate Tah is zero or below and the remaining refrigerant liquid amount Ms exceeds zero while the compressor is in a stopped state, a second heating operation is started, the compressor heating portion 10 is controlled based on the remaining refrigerant liquid amount Ms, and the refrigerant condensed in the compressor 1 is evaporated.

Abstract: A control device that controls a plurality of air conditioners includes a data memory section for storing performance model data representing the relationship between air conditioning capability and power consumption for each of the plurality of air conditioners. An overall air conditioning load calculating section calculates an overall load that is the sum of air conditioning loads of the plurality of air-conditioning apparatuses. An air conditioning capability allocation calculating section an air conditioning capability for each of the plurality of air conditioners on the basis of the performance model data and the overall load so that the sum of the air conditioning capability of the plurality of air conditioners is the overall load and the sum of the power consumption of the plurality of air conditioners is minimum. A control signal section sends a control signal related to the air conditioning capability to each of the plurality of air conditioners.

Abstract: While a compressor is stopped, a change rate of a refrigerant temperature per predetermined time is calculated on the basis of a value detected by a refrigerant temperature sensor, and a heating amount from a compressor heating unit to the compressor is made proportional to the change rate of the refrigerant temperature.

Abstract: A selection unit switches between a phase ?p and a phase ?n different from the phase ?p substantially by 180 degrees, and outputs one of them in synchronization with a carrier signal. A voltage-command generation unit generates and outputs three-phase voltage command values Vu*, Vv* and Vw* based on the phase outputted by the selection unit. A PWM-signal generation unit generates three-phase voltage command values Vu*?, Vv*? and Vw*? by correcting the three-phase voltage command values Vu*, Vv* and Vw* outputted by the voltage-command generation unit according to a predetermined method, and generates six drive signals corresponding to switching elements of the inverter based on the three-phase voltage command values Vu*?, Vv*? and Vw*? and the carrier signal. The PWM-signal generation unit outputs the generated drive signals to the corresponding switching elements of the three-phase inverter, to cause the inverter to generate a high-frequency AC voltage.

Abstract: An adder adds a phase ?plus, which is n times a size of 60 degrees, to a phase output from a phase switching unit and outputs the phase as a voltage command phase ?. A voltage generation unit generates voltage command value based on the voltage command phase output by the adder and outputs the command value. A drive-signal generation unit, based on an output from the voltage generation unit generates drive signals corresponding to respective switching elements of an inverter, and outputs respective generated drive signals to the corresponding switching elements of the inverter, and generates a high-frequency AC voltage in the inverter.

Abstract: To obtain an air-conditioning apparatus that appropriately determines the state of stagnating refrigerant in a compressor, and suppresses power consumption while the air-conditioning apparatus is not in operation. When a compressor temperature change rate is determined to be higher than a refrigerant temperature change rate, a controller identifies that liquid refrigerant in a lubricant oil in a compressor has been totally gasified, stops energizing a motor unit, and ends a heating operation of the compressor.

Abstract: When a compressor is in a stopped state and an outside air temperature change rate Tah exceeds zero, a first heating operation is started, and a heating capacity of a compressor heating portion is set in a range not more than a heating capacity upper limit Pmax based on the outside air temperature change rate Tah. A remaining refrigerant liquid amount Ms condensed in the compressor that had not been evaporated is acquired based on the outside air temperature change rate Tah and the heating capacity. If the outside air temperature change rate Tah is zero or below and the remaining refrigerant liquid amount Ms exceeds zero while the compressor is in a stopped state, a second heating operation is started, the compressor heating portion 10 is controlled based on the remaining refrigerant liquid amount Ms, and the refrigerant condensed in the compressor 1 is evaporated.

Abstract: A control device that controls a plurality of air conditioners includes a data memory section for storing performance model data representing the relationship between air conditioning capability and power consumption for each of the plurality of air conditioners. An overall air conditioning load calculating section calculates an overall load that is the sum of air conditioning loads of the plurality of air-conditioning apparatuses. An air conditioning capability allocation calculating section an air conditioning capability for each of the plurality of air conditioners on the basis of the performance model data and the overall load so that the sum of the air conditioning capability of the plurality of air conditioners is the overall load and the sum of the power consumption of the plurality of air conditioners is minimum. A control signal section sends a control signal related to the air conditioning capability to each of the plurality of air conditioners.