An air conditioner unit includes a refrigeration loop including a condenser and an evaporator, a compressor for circulating refrigerant, and an electronic expansion valve. A controller monitors an operating superheat of the refrigerant across the evaporator, identifies a superheat fault condition based on at least one of the operating superheat, a target valve position of the electronic expansion valve, or a compressor speed, stops the compressor in response to identifying the superheat fault condition, and initiates a calibration process of the electronic expansion valve.

Embodiments of the present invention provide a method for controlling compressor braking, a frequency converter and a variable speed compressor. The method includes steps of: determining to brake a compressor, wherein a brake circuit includes three switching units and the three switching units are respectively electrically connected to three phases of windings of a motor of the compressor; actuating two of the three switching units to short-circuit two phases of windings of the motor. The two phases of windings of the motor are short-circuited by controlling the three switching units to generate braking torque, such that the compressor is braked without introducing a DC voltage, and thus the braking energy consumption is reduced. Besides, by turning on only two switches at a time, the switching abrasion is reduced, and the overall service life of the three switching units is effectively improved.

Operating a vapor compression system including determining a total heat delivered by the vapor compression system, determining a total electrical energy consumed by the vapor compression system while delivering heat, maintaining a total electrical energy consumed by the vapor compression system during a defrosting cycle, determining a cumulative coefficient of performance of the vapor compression system based on the total heat delivered, the total electrical energy consumed by the vapor compression system while delivering heat, and the total electrical energy consumed by the vapor compression system during the defrosting cycle, and initiating a defrosting cycle based the cumulative coefficient of performance.

There is disclosed a refrigeration system comprising a refrigeration circuit that includes a compressor, a condenser, an expansion valve and an evaporator. A condenser fan of the refrigeration system is configured to operate, under the control of a controller, at a condenser fan speed that is set based on a current refrigeration demand on the system.

Variable volume ratio compressors may be controlled using a switching parameter based on compressor speed and suction density to improve the matching of compressor volume ratio to desired discharge conditions. Delay periods may be implemented in the determination of when to change volume ratio to control the frequency of changes to the volume ratio. The switching parameter may be a product of the compressor speed and suction density. The volume ratio of the compressor may be controlled by switching valves directing pressure to a piston of a variable volume ratio system of the compressor.

The disclosure describes a compressor housing of a centrifugal compressor. The compressor housing includes a main housing portion and an end housing portion separate from the main housing portion. The main housing portion and the end housing portion are configured to interface at a mating surface of the respective housing portions. The mating surface of the respective housing portions is configured to provide a hermetically sealable surface between the main housing portion and the end housing portion. The main housing portion includes an outlet port configured to discharge compressed vapor refrigerant. The outlet port is configured to receive an adaptor from outside the compressor housing.

A method of determining charge loss of a refrigeration system includes the steps of inputting an ambient temperature, a box temperature, and a compressor speed into an electronic controller of the refrigeration system, and calculating a first air side temperature difference across an evaporator by applying an algorithm having a first T-Map representative of normal operating conditions. The controller may then confirm a detection prerequisite is satisfied. Upon confirmation, the controller calculates a second air side temperature difference across the evaporator by applying the algorithm having a second T-Map representative of a loss of refrigerant charge. An action may then be taken from the controller if the first air side temperature difference is less than the second air side temperature difference.

A current estimating device that estimates a capacitor current of a high-voltage circuit for driving a motor, wherein the current estimating device calculates a voltage utilization rate using the input voltage of an inverter included in the high-voltage circuit and the speed of the motor, calculates a first constant by applying the voltage utilization rate to a predetermined first arithmetic expression, and calculates the capacitor current of an electrical condenser included in the high-voltage circuit by multiplying the first constant by a motor current effective value.

An air conditioner and a method for controlling the same are disclosed. The air conditioner implements a multistage expansion scheme by implementing serial connection between electronic expansion valves including in the R410A refrigerant-based air conditioner, and thus guarantees an optimum compression ratio in all cooling/heating load regions. Therefore, although cycle characteristics are changed by changing R410A refrigerant to R32 refrigerant, the air conditioner optimizes the cycle simply by controlling a degree of opening of electronic expansion valves, respectively. As described above, since the cycle optimization is implemented using the multistage expansion scheme in which legacy electronic expansion valves are coupled in series, the design modification is minimized without design modification of requisite constituent elements such as a heat exchanger, system implementation is facilitated, resulting in high efficiency in cost and productivity. Cooling/heating performance improvement and reliability guarantee are achieved under all load conditions, resulting in increased system efficiency.

There is disclosed a vehicle air-conditioning device in which a refrigerant subcool degree in a radiator is appropriately controlled, so that comfortable and efficient vehicle interior air conditioning is achievable. The vehicle air-conditioning device executes a heating mode in which a controller lets a refrigerant discharged from a compressor 2 radiate heat in a radiator 4, decompresses the refrigerant by which heat has been radiated by an outdoor expansion valve 6, and then lets the refrigerant absorb heat in an outdoor heat exchanger 7. In the heating mode, the vehicle air-conditioning device controls a refrigerant subcool degree SC of the radiator 4 by the outdoor expansion valve 6. On a basis of a radiator inlet air temperature THin that is a temperature of the air flowing into the radiator 4, the controller corrects a target subcool degree TGSC that is a target value of the refrigerant subcool degree SC in the radiator 4 in a lowering direction, as the radiator inlet air temperature THin rises.