A system is provided for adjusting the volume ratio of a screw compressor. The system can use a port in a rotor cylinder to bypass vapor from the compression chamber to the discharge passage of the compressor. A valve can be used to open or close the port to obtain different volume ratios in the compressor.

Screw compressor with a compression chamber that is formed by a compression housing, in which a pair of meshed helical compressor rotors in the form of a screw are rotatably mounted and with a drive motor that is provided with a motor chamber formed by a motor housing, in which a motor shaft is rotatably mounted, and this motor shaft drives at least one of the aforementioned two compressor rotors, whereby the compression housing and the motor housing are connected directly together to form a compressor housing, whereby the motor chamber and the compression chamber are not sealed off from one another and whereby the rotor shafts of the compressor rotors, as well as the motor shaft, extend along axial directions that are oblique or transverse to the horizontal plane.

Screw compressor with a compression chamber that is formed by a compression housing, in which a pair of meshed helical compressor rotors in the form of a screw are rotatably mounted and with a drive motor that is provided with a motor chamber formed by a motor housing, in which a motor shaft is rotatably mounted, and this motor shaft drives at least one of the aforementioned two compressor rotors, whereby the compression housing and the motor housing are connected directly together to form a compressor housing, whereby the motor chamber and the compression chamber are not sealed off from one another and whereby the rotor shafts of the compressor rotors, as well as the motor shaft, extend along axial directions that are oblique or transverse to the horizontal plane.

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 method for controlling a compressor towards an unloaded state, in which the compressor includes a compressor element (2) with an inlet (5), in which in the unloaded state, a residual flow (QD) is suctioned via the inlet (5) towards and into the compressor element (2), and in which for a transition from a loaded state of the compressor to the unloaded state, the inlet (5) of the compressor element (2) is partially closed in successive discrete transitional steps.

A method including: determining a cooling value; and comparing the cooling value to an activation point of a lead compressor. The lead compressor is in a tandem set of scroll compressors of a cooling system. The tandem set of compressors comprises a lag compressor. The method further includes: activating the lead compressor when the cooling value is greater than the activation point; activating the lag compressor subsequent to activating the lead compressor; and determining whether conditions exist including: an alarm associated with the lag compressor being generated, and the lead compressor being deactivated. The method further includes deactivating the lag compressor when at least one of the conditions exists in the cooling system.

A method including: determining a cooling value; and comparing the cooling value to an activation point of a lead compressor. The lead compressor is in a tandem set of scroll compressors of a cooling system. The tandem set of compressors comprises a lag compressor. The method further includes: activating the lead compressor when the cooling value is greater than the activation point; activating the lag compressor subsequent to activating the lead compressor; and determining whether conditions exist including: an alarm associated with the lag compressor being generated, and the lead compressor being deactivated. The method further includes deactivating the lag compressor when at least one of the conditions exists in the cooling system.

A compressor is provided and includes a shell, a compression mechanism, a motor, a data module, and a compressor controller. The data module includes a data module processor and a data module memory. The compressor controller includes a controller processor and a controller memory distinct from the data module processor and the data module memory. The data module receives sensed data, stores the sensed data in the data module memory, determines a first diagnosis of the compressor based on the sensed data, and communicates the sensed data and the first diagnosis to the compressor controller. The compressor controller determines a second diagnosis of the compressor based on the sensed data and verifies the first diagnosis by comparing the first diagnosis to the second diagnosis.

A method of operating an exhaust gas recirculation pump for an internal combustion engine including: providing an EGR pump assembly including an electric motor coupled to a roots device having rotors, the EGR pump operably connected to an internal combustion engine; providing an EGR control unit lined to the EGR pump assembly; providing sensors linked to the EGR control unit; determining if a motor speed is within a predetermined target (step SI), wherein when the motor speed is within the predetermined target then; determining if a motor torque is within a predetermined target (step S2) wherein when the motor torque is within the predetermined target then; determining if a motor temperature is within a predetermined target (step S3) wherein when the motor temperature is within the predetermined target then; maintaining operation of the exhaust gas recirculation pump.