According to one embodiment, a rotary shaft of a rotary compressor includes a first connection shaft and a second connection shaft. The first connection shaft has a cross-sectional shape including a first outer surface, a second outer surface, and a third outer surface. L1 represents a distance from an intersecting point located on one end side where the first outer surface and the second outer surface intersect each other to the rotation center, L2 represents a distance from an intersecting point located on an other end side where the first outer surface and the second outer surface intersect each other, to the rotation center, and L3 represents a distance from the third outer surface to the rotation center, a relationship of L1>L3≥L2 is satisfied.

According to one embodiment, a rotary shaft of a rotary compressor includes a first connection shaft and a second connection shaft. The first connection shaft has a cross-sectional shape including a first outer surface, a second outer surface, and a third outer surface. L1 represents a distance from an intersecting point located on one end side where the first outer surface and the second outer surface intersect each other to the rotation center, L2 represents a distance from an intersecting point located on an other end side where the first outer surface and the second outer surface intersect each other, to the rotation center, and L3 represents a distance from the third outer surface to the rotation center, a relationship of L1>L3≥L2 is satisfied.

Method to operate a vacuum system comprising at least a first vacuum pump and a second vacuum pump wherein the first vacuum pump and the second vacuum pump are connectable to a vacuum chamber to maintain a set pressure inside the vacuum chamber. The first vacuum pump is a Variable Speed Drive pump wherein the first vacuum pump and the second vacuum pump are connected in series. The method comprises the steps of controlling the performance of the first vacuum pump and the performance of the first vacuum pump is controlled to be equal to or higher than the performance of the second vacuum pump while maintaining the set pressure in the vacuum chamber.

Method to operate a vacuum system comprising at least a first vacuum pump and a second vacuum pump wherein the first vacuum pump and the second vacuum pump are connectable to a vacuum chamber to maintain a set pressure inside the vacuum chamber. The first vacuum pump is a Variable Speed Drive pump wherein the first vacuum pump and the second vacuum pump are connected in series. The method comprises the steps of controlling the performance of the first vacuum pump and the performance of the first vacuum pump is controlled to be equal to or higher than the performance of the second vacuum pump while maintaining the set pressure in the vacuum chamber.

A compressor and an air conditioning system. The compressor includes a low-pressure-stage compressor body and a high-pressure-stage compressor body, where the low-pressure-stage compressor body is provided with a low-pressure-stage suction port and a low-pressure-stage exhaust port, the high-pressure-stage compressor body is provided with a high-pressure-stage suction port and a high-pressure-stage exhaust port, a communication pipeline is arranged between the low-pressure-stage exhaust port and the high-pressure-stage suction port, the low-pressure-stage suction port communicates with a low-pressure-stage gas source, and the high-pressure-stage suction port has a first state of communication with the low-pressure-stage exhaust port and a second state of communication with the low-pressure-stage gas source.

The invention relates to a method for controlling a rotary screw compressor, having at least a first and a second air-end, wherein both air-ends are driven separately from one another and speed controlled. According to the invention, the following steps are carried out: detection of a volume flow taken at the outlet of the second air-end; adjustment of the rotational speed of both air-ends, when the removed volume flow fluctuates in a range between a maximum value and a minimum value; opening of a pressure-relief valve, if the volume flow falls below the minimum value; and reduction of the rotational speed of at least the first air-end to a predetermined idling speed (V1.sub.L) to reduce the volumetric flow delivered by the first to the second air-end.

The invention relates to a method for controlling a rotary screw compressor, having at least a first and a second air-end, wherein both air-ends are driven separately from one another and speed controlled. According to the invention, the following steps are carried out: detection of a volume flow taken at the outlet of the second air-end; adjustment of the rotational speed of both air-ends, when the removed volume flow fluctuates in a range between a maximum value and a minimum value; opening of a pressure-relief valve, if the volume flow falls below the minimum value; and reduction of the rotational speed of at least the first air-end to a predetermined idling speed (V1.sub.L) to reduce the volumetric flow delivered by the first to the second air-end.

A refrigeration cycle device according to the present invention includes a compressor having a first compression chamber and a second compression chamber, a condenser, a decompressor, an evaporator, an injection path configured to introduce intermediate pressure refrigerant, a communication passage configured to introduce intermediate pressure refrigerant compressed in the first compression chamber to the second compression chamber, and a switch element configured to selectively make the second compression chamber communicate with the evaporator or make the second compression chamber communicate with the communication passage. The injection path introduces the intermediate pressure refrigerant to the second compression chamber. Single-stage compressing operation is performed when the second compression chamber is communicated with the evaporator, and two-stage compressing operation is performed when the second compression chamber is communicated with the communication passage.

Method for controlling a compressed air unit which consists of several compressed air networks (2 and 3) having at least one commonly controllable component, characterized in that, on the basis of measurement data of at least one of the above-mentioned compressed air networks (2 and 3), at least the above-mentioned common component (11) is controlled by at least one controller (20).

Method for controlling a compressed air unit which consists of several compressed air networks (2 and 3) having at least one commonly controllable component, characterized in that, on the basis of measurement data of at least one of the above-mentioned compressed air networks (2 and 3), at least the above-mentioned common component (11) is controlled by at least one controller (20).