A vapor compression system includes a compressor configured to circulate a refrigerant through a refrigerant loop, a sump configured to receive a mixture of lubricant and the refrigerant from the compressor, and a controller having a memory and a processor. The processor is configured to receive a first signal indicative of a temperature of the mixture within the sump, receive a second signal indicative of a pressure of the mixture within the sump, determine a relative amount of the refrigerant in the mixture based on the first signal and the second signal, and output a control signal in response to the relative amount of the refrigerant in the mixture exceeding a threshold value.

A refrigeration machine control device according to an embodiment of the present invention serves to control a turbo refrigeration machine and is equipped with a pressure reduction rate identification unit for identifying a pressure reduction rate at which foaming does not occur in an oil tank, and a pressure adjustment unit for adjusting the pressure of an evaporator on the basis of the identified pressure reduction rate. The pressure reduction rate identification unit is equipped with: a refrigerant precipitation gas volume calculation unit for calculating the volume of refrigerant gas precipitated from lubricating oil when the pressure is reduced at a prescribed pressure reduction rate; and a determination unit for determining whether or not foaming is permissible on the basis of a comparison between the calculated volume and the volume on the surface of the oil in the oil tank.

In order to reduce the effect on a compressor caused by foaming in an oil tank, a control unit for controlling an oil pump starts the oil pump before a compressor is started (SA1), starts the compressor (SA4) when an oil supply differential pressure P satisfies a compressor startup condition during a reference time Tas from the starting of the oil pump (“Yes” in SA3), and extends the operation of the oil pump for a prescribed time without starting the compressor (Step SA5) when the compressor startup condition is not satisfied (“No” in SA3).

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.

An air compressor includes a tank unit that stores compressed air, a motor unit that generates compressed air to be stored in the tank unit, a pressure detection unit that detects a pressure value in the tank unit, and a control unit that drives the motor unit when a pressure value in the tank unit detected by the pressure detection unit is equal to or less than a motor start pressure value, and stops the motor unit when the pressure value in the tank unit detected by the pressure detection unit is equal to or greater than a motor stop pressure value. The control unit changes at least either of the motor start pressure value or the motor stop pressure value every time when a predetermined time passed.

In order to reduce the effect on a compressor caused by foaming in an oil tank, a control unit for controlling an oil pump starts the oil pump before a compressor is started (SA1), starts the compressor (SA4) when an oil supply differential pressure P satisfies a compressor startup condition during a reference time Tas from the starting of the oil pump (“Yes” in SA3), and extends the operation of the oil pump for a prescribed time without starting the compressor (Step SA5) when the compressor startup condition is not satisfied (“No” in SA3).

A refrigeration machine control device according to an embodiment of the present invention serves to control a turbo refrigeration machine and is equipped with a pressure reduction rate identification unit for identifying a pressure reduction rate at which foaming does not occur in an oil tank, and a pressure adjustment unit for adjusting the pressure of an evaporator on the basis of the identified pressure reduction rate. The pressure reduction rate identification unit is equipped with: a refrigerant precipitation gas volume calculation unit for calculating the volume of refrigerant gas precipitated from lubricating oil when the pressure is reduced at a prescribed pressure reduction rate; and a determination unit for determining whether or not foaming is permissible on the basis of a comparison between the calculated volume and the volume on the surface of the oil in the oil tank.

Systems and methods for a vapor compression system including primary actuators, secondary actuators, primary sensors that provide a primary set of system outputs, and secondary sensors that provide a secondary set of system outputs. A primary controller receives the primary set of system outputs, and produces a primary set of control inputs for the primary actuators, to regulate one or more zone temperatures to set-points and to regulate one or more critical process variables to set-points. A secondary controller receives the secondary set of system outputs, and produces a secondary set of control inputs, to minimize an overall system power consumption. The secondary inputs may include set-points to the primary controller. The primary outputs may include estimates of critical process variables that are used as inputs to the secondary controller.

A refrigeration system, a fault diagnosis system and a fault diagnosis method for the refrigeration system, a controller and a storage medium. The fault diagnosis method includes: receiving a fault alarm sent by an associated refrigeration system, and acquiring a fault cause list associated with the fault alarm; determining whether to run a fault diagnosis system associated with the fault alarm; and when the fault diagnosis system associated with the fault alarm is run, checking the associated refrigeration system sequentially according to the fault cause list, and acquiring a fault cause and a repair means list associated with the fault cause.

A method of operating a multiple-compressor refrigeration system is provided. This method includes the steps of supplying, via a common supply line, refrigerant gas and oil to a plurality of compressors coupled in series, and attaching an oil flow conduit between adjacent compressors of the plurality of compressors. The oil flow conduit is configured to move oil from a compressor with a relatively higher pressure to a compressor with a relatively lower pressure. The method further includes controlling the pressure for each of the plurality of compressors by regulating a speed at which each of the plurality of compressors operates in order to maintain a pressure differential between the adjacent compressors to facilitate the flow of oil from the compressor with the relatively higher pressure to the compressor with the relatively lower pressure.