A compressor fault diagnostic apparatus including a current sensing unit to sense a current flowing through a motor of the compressor, a fault diagnostic unit to determine whether or not the motor performs a reverse rotation based on the current flowing through the motor, and a cut-off unit to remove power based on a determination of the fault diagnostic unit.

Provided is an air-conditioning apparatus configured so that a decrease in a refrigeration capacity can be suppressed without increasing the amount of refrigerant with which a refrigerant circuit is filled and that refrigerant can be suitably stored during a pump down operation. The air-conditioning apparatus includes a first on-off valve provided at a pipe between an expansion valve and a use side heat exchanger, a bypass branching from a pipe between the expansion valve and the first on-off valve and connected to a pipe at a suction-side of a compressor, and a refrigerant storage unit configured to store the refrigerant having passed through the bypass. In a pump down operation in which the compressor operates with the first on-off valve being in a closed state, the refrigerant having flowed out from the heat source side heat exchanger flows into the bypass, and then, is stored in the refrigerant storage unit.

An air conditioner is provided that reduces user discomfort due to vibrations and noises at a compressor, piping, and the like such as of an air conditioner. To achieve this, an air conditioner includes: a compressor (10) that has a motor (12) and a compression mechanism (14) driven by the motor (12); a speed detector (43) that detects a rotation speed of the motor (12); a drive mode controller (48) that controls a drive mode of the motor (12); and refrigerant piping that is connected to the compression mechanism (14) and allows a refrigerant to flow therethrough, wherein the drive mode controller (48), for stopping the motor (12), decelerates the motor (12) to a rotation speed equal to or lower than a resonance frequency between the compression mechanism (14) and the refrigerant piping.

A refrigeration cycle apparatus includes a refrigeration cycle circuit, a liquid receiver, a first valve and a second valve. The refrigeration cycle circuit includes a compressor, an outdoor heat exchanger and an indoor heat exchanger. The liquid receiver is provided in a second section located in the refrigeration cycle circuit. The second section is a section extending between the outdoor heat exchanger and the indoor heat exchanger without extending through the compressor. The first valve is provided in a first section in the refrigeration cycle circuit, and is a solenoid valve or a motor valve. The first section is a section extending between the outdoor heat exchanger and the indoor heat exchanger through the compressor. The second valve is provided in the second section and between the liquid receiver and the indoor heat exchanger, and is an electronic expansion valve, a solenoid valve or a motor valve.

An air conditioner is provided that reduces user discomfort due to vibrations and noises at a compressor, piping, and the like such as of an air conditioner. To achieve this, an air conditioner includes: a compressor (10) that has a motor (12) and a compression mechanism (14) driven by the motor (12); a speed detector (43) that detects a rotation speed of the motor (12); a drive mode controller (48) that controls a drive mode of the motor (12); and refrigerant piping that is connected to the compression mechanism (14) and allows a refrigerant to flow therethrough, wherein the drive mode controller (48), for stopping the motor (12), decelerates the motor (12) to a rotation speed equal to or lower than a resonance frequency between the compression mechanism (14) and the refrigerant piping.

In a method for operating a compressor (22) having an inlet (26) and an outlet (28), the method includes: running the compressor to compress a fluid; shutting down (422) the compressor; determining (420) a condition-dependent threshold restart pressure difference (threshold) across the compressor; relieving the pressure-difference to reach the threshold; and, after the threshold is reached, restarting (434) the compressor.

A climate-control system may include a compressor and a control module. The compressor includes a motor driving a compression mechanism to compress a working fluid. The control module is in communication with the motor and may be configured to determine a balance speed of the motor at which a forward-rotational inertial force of the compression mechanism is equal to a backward-rotational gas force on the compression mechanism. The control module may be configured to adjust a running speed of the motor to the balance speed after receipt of a compressor-shutdown-command and before shutting down the compressor.

Systems and methods of operating a refrigeration system including initiating a compressor shutdown operation (302), recording shutdown conditions (304), calculating one or more restart characteristics based on the recorded shutdown conditions (306), comparing the calculated restart characteristics with one or more compressor restart safety limits (308), when the calculated restart characteristics do not satisfy the restart safety limits, performing a temperature modulation pump down operation (310), and when the calculated restart characteristics satisfy the restart safety limits, completing the compressor shutdown operation (312).

Provided is an air-conditioning apparatus configured so that a decrease in a refrigeration capacity can be suppressed without increasing the amount of refrigerant with which a refrigerant circuit is filled and that refrigerant can be suitably stored during a pump down operation. The air-conditioning apparatus includes a first on-off valve provided at a pipe between an expansion valve and a use side heat exchanger, a bypass branching from a pipe between the expansion valve and the first on-off valve and connected to a pipe at a suction-side of a compressor, and a refrigerant storage unit configured to store the refrigerant having passed through the bypass. In a pump down operation in which the compressor operates with the first on-off valve being in a closed state, the refrigerant having flowed out from the heat source side heat exchanger flows into the bypass, and then, is stored in the refrigerant storage unit.

A refrigerant circuit of a refrigeration cycle apparatus has a compressor, a cooling-heating switching mechanism, a condenser, a refrigerant expansion mechanism, and an evaporator. During operation of the compressor, the refrigerant expansion mechanism opens the refrigerant circuit, a first three-way valve connects an outlet of the compressor to the condenser, and a second three-way valve connects an inlet of the compressor to the evaporator. During stop of the compressor, the refrigerant expansion mechanism closes the refrigerant circuit, the first three-way valve connects the outlet of the compressor to the evaporator, and the second three-way valve connects the inlet of the compressor to the evaporator.