The present invention is provided with: a turbo compressor that compresses a refrigerant; a condenser that condenses the refrigerant compressed by the turbo compressor; an expansion valve that expands a liquid refrigerant introduced from the condenser; an evaporator that evaporates the refrigerant expanded by the expansion valve; an oil tank that stores a lubricating oil supplied to the turbo compressor; a pressure equalizing pipe that connects the oil tank and the evaporator; and a control unit that controls start-up. The control unit calculates the amount of a refrigerant eluded into the lubricating oil in the oil tank at the time of start-up, and reduces a pressure reduction speed in the oil tank by limiting the opening operation of an IGV when the refrigerant elution amount per prescribed time exceeds a prescribed value.

A climate-control system may include a compressor, a condenser, an evaporator, a first sensor, a second sensor, a third sensor, and a control module. The compressor may include a motor and a compression mechanism. The condenser receives compressed working fluid from the compressor. The evaporator is in fluid communication with the compressor and disposed downstream of the condenser and upstream of the compressor. The first sensor may detect an electrical operating parameter of the motor. The second sensor may detect a discharge temperature of working fluid discharged by the compression mechanism. The third sensor may detect a suction temperature of working fluid between the evaporator and the compression mechanism. The control module is in communication with the first, second and third sensors and may determine whether a refrigerant floodback condition is occurring in the compressor based on data received from the first, second and third sensors.

The purpose of the present invention is to provide a refrigeration machine wherein lubricating oil supplied to a bearing, etc. in a turbo compressor is capable of being cooled by a simple configuration. This refrigeration machine (1) comprises: a refrigeration cycle in which a refrigerant circulates, the refrigeration cycle being provided with a turbo compressor (2) having a compression mechanism driven by a motor, the refrigeration cycle being further provided with a condenser (3) and an evaporator (8); an oil tank (23) in which lubricating oil is stored; a lubricating oil supply line (22) for supplying lubricating oil from the oil tank (23) into a motor housing (31) containing the motor; and a liquid refrigerant supply line (24) for supplying a refrigerant from the condenser (3) into the motor housing (31).

A device for storing refrigerant of a refrigeration circuit and a method of operating the device, in particular for an air conditioning system of a motor vehicle. The device has a housing having a volume-enclosing wall with an inlet for introducing a refrigerant-oil mixture, and an outlet, a refrigerant discharge line arranged in the interior of the housing with an inlet opening arranged above a liquid level of the refrigerant for receiving gaseous refrigerant, and a system for returning oil to a compressor having at least one through hole formed below the liquid level of the refrigerant, in particular below a filling level of the oil, in the refrigerant discharge line. In addition, at least one through hole formed in the refrigerant discharge line is formed with an adjustable through-flow cross section, which can be varied by means of a closing apparatus.

A preheater for a compressor that is capable of heating a lubricant oil efficiently with smaller power is provided. A preheater for a compressor includes: a capacitive oil surface sensor that is provided at a compressor used in a refrigerating cycle, and detects an oil surface of a lubricant oil A in the compressor; and a power supply unit that applies high-frequency voltage to the oil surface sensor.

An air-conditioning apparatus includes: a refrigerant circuit in which a compressor, a four-way valve, a heat source-side heat exchanger, an expansion valve and a load-side heat exchanger are connected; and a controller which controls a refrigeration cycle in which refrigerant is circulated in the refrigerant circuit, to switch a flow passage for the refrigerant in accordance with which of a cooling operation, a heating operation and a defrosting operation is performed. The controller includes: a refrigeration-cycle control unit which controls the four-way valve to switch the flow passage of the refrigerant when the operation to be performed is switched from the heating operation to the defrosting operation; and a compressor control unit which sets an operation frequency of the compressor at a value lower than an operation frequency which is applied during the heating operation, when the operation is switched from the heating operation to the defrosting operation.

A screw compressor system for a utility vehicle has at least one screw compressor, at least one screw compressor drive, at least one temperature probe and at least one control and regulation unit. The control and/or regulation unit is connected to the screw compressor drive and to the temperature probe and is designed and configured such that it controls, in accordance with a temperature threshold signal obtained from the temperature probe, the screw compressor drive with respect to a rotational speed.

In order to improve a refrigerant compressor comprising a drive motor and a compressor unit which compresses a refrigerant entering through a suction inlet and allows it to exit through a pressure outlet in such a way that it works as reliably as possible, it is proposed that the refrigerant compressor comprise a compressor monitoring system which is integrated into a compressor control system and which determines a compressor condition by means of a first condition value that corresponds to a first saturation temperature in the suction inlet and a second condition value that corresponds to a second saturation temperature in the pressure outlet, and which compares the compressor condition with permissible compressor conditions lying in a given deployment field of a deployment diagram and initiates a process of switching-off the refrigerant compressor if the compressor condition departs from the deployment field.

A refrigerant compressor for refrigeration plants having a compressor unit driven by a drive unit. At least one of the compressor and drive units has a control unit which is controllable by delivery rate control system to control the refrigerant compressor at different delivery rates. An external delivery rate setpoint value is communicated to the delivery rate control system to prevent critical operating states. The delivery rate control system is configured to acquire, via a sensor, a compressor unit reference temperature. The delivery rate control system is configured to ascertain an operating state value group to acquire an operating state of the refrigerant compressor, and specify a delivery rate for operation of the refrigerant compressor outside of the critical operating states, if the value of the ascertained operating state value group based upon the compressor reference temperature permits a critical operating state of the refrigerant compressor.

A compressor (31a, 31b) and an oil separator (35a, 35b) are provided in a refrigerant circuit (20). A flow-rate regulating valve (41a, 41b) is provided in an oil return pipe (40a, 40b) for returning a refrigerating-machine oil in the oil separator (35a, 35b) to the compressor (31a, 31b). A temperature sensor (42a, 42b) is provided downstream of the flow-rate regulating valve (41a, 41b) in the oil return pipe (40a, 40b). The oil-amount determiner (71a, 71b) determines whether an oil shortage state in which the amount of the refrigerating-machine oil held by the compressor (31a, 31b) is insufficient is present, on the basis of a measured value obtained by the temperature sensor (42a, 42b).