Refrigeration device intended to extract heat from at least one member by heat exchange with a working fluid circulating in the working circuit comprising in series: a fluid compression mechanism a fluid cooling mechanism, preferably isobaric or substantially isobaric, a fluid expansion mechanism, and a fluid heating mechanism, in which device the compression mechanism is of the centrifugal compression type and consists of two compression stages arranged in series in the circuit, the device comprising two respective electric drive motors driving the two compression stages, the expansion mechanism consisting of a turbine coupled to the motor of one of the compression stages, the turbine of the expansion mechanism being coupled to the drive motor of the first compression stage.

A method for controlling a heat pump system. The heat pump system includes a compressor for compressing a working fluid of the heat pump system and an electric motor for providing an output torque for driving the compressor. The method includes the steps of recovering heat emitted from the electric motor by heating the working fluid, providing a first control mode and a second control mode for the electric motor, and controlling the electrical motor in a way creating higher heat losses of the electric motor for a given output torque of the electric motor in the second control mode than in the first control mode.

A photovoltaic air conditioner control method and apparatus and a photovoltaic air conditioner. The method includes: detecting in real time the grid-connected side inverter module temperature and the grid-connected side current of a photovoltaic air conditioner; determining the interval in which the grid-connected inverter module temperature is located and the interval in which the grid-connected side current is located; and, on the basis of the determining results, performing frequency-limiting and frequency-reduction control of the photovoltaic air conditioner.

An engine system including: an engine configured to output shaft power by burning fuel, and a system main portion configured to operate using the shaft power of the engine. The engine system further includes: an operation controlling unit, and a power source unit configured to convert commercial power to operating power and supply the operating power to the operation controlling unit. The power source unit includes: a system main portion-side power source unit configured to supply operating power for controlling the operation of the system main portion, and an engine-side power source unit configured to supply operating power for controlling the operation of the engine. The system main portion-side power source unit and the engine-side power source unit are provided individually and separately from each other.

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.

A refrigerant compressor according to an exemplary aspect of the present disclosure includes, among other things, a first stage and a second stage downstream of the first stage, and a cooling line configured to cool power electronics. The cooling line is configured to be switched between a first mode and a second mode. The first mode is configured to dump refrigerant between the first stage and the second stage, and the second mode is configured to dump refrigerant upstream of the first stage.

A motor-driven compressor includes a compression portion, an electric motor, an inverter, and a metal housing. The inverter includes three-phase switching elements and a plastic holder that retains the three-phase switching elements. The housing includes a thermal radiation surface. The holder includes a metal spring. The holder is fixed to the housing using two fasteners. The three-phase switching elements are laid out between the two fasteners. The switching elements at opposite ends of the three-phase switching elements are pressed toward the thermal radiation surface by only the holder. The switching element at the middle of the three-phase switching elements is pressed toward the thermal radiation surface by the holder and the spring.

The motor-driven compressor includes an electric motor, a housing, a compression portion, and an inverter device. The inverter device includes an inverter circuit, a current sensor, a coordinate converter, a speed controller, a current controller, a PWM controller, and a rotation angle estimator. The speed controller generates a d-axis current command value and a q-axis current command value such that a necessary torque to drive the electric motor occurs. The inverter device includes a heat-generating current command section that increases a temperature of the electric motor by changing the d-axis current command value and the q-axis current command value. The heat-generating current command section changes the d-axis current command value and the q-axis current command value so as to shift them in a direction in which a d-axis current value increases along a constant torque curve in a d-q coordinate system.

Methods are directed towards dynamically determining refrigerant film thickness at the rolling-element bearing and for dynamically controlling refrigerant film thickness at the rolling-element bearing. Further, an oil free chiller system is configured for dynamically determining refrigerant film thickness at the rolling-element bearing of the oil free chiller system, wherein the oil free chiller system is also configured for dynamically controlling refrigerant film thickness at the rolling-element bearing of the oil free chiller system.

A refrigerator includes a controller that is configured to perform operations including driving a refrigerator compartment compressor, determining whether a sensed temperature in the refrigerator compartment satisfies a first temperature, driving, based on the sensed temperature in the refrigerator compartment satisfying the first temperature, a freezer compartment compressor, stopping the refrigerator compartment compressor, maintaining, after stopping the refrigerator compartment compressor, operation of the freezer compartment compressor, restarting the refrigerator compartment compressor, and varying a driving frequency of the refrigerator compartment compressor.