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.

An eccentric screw pump hasa pump housing having a pump inlet opening and a pump outlet opening, a stator disposed in the pump housing, a rotor disposed in the stator, a drive unit comprising a drive motor and a driveshaft which for transmitting a torque connects the drive motor to the rotor, wherein the rotor for a rotating movement about a rotating axle is guided in the stator, a state sensor for detecting a state variable of the eccentric screw pump, where the state sensor, for detecting a state variable on the rotor or on the driveshaft, is disposed on the rotor or the driveshaft, or is connected to the rotor or the driveshaft by means of a signal line and is disposed so as to be spaced apart from the rotor or the driveshaft.

A method of operating a compressor includes obtaining a mechanical angle and an angular speed of a rotor, determining an amplitude of a fundamental harmonic of a periodic load torque exerted on the rotor based at least in part on the mechanical angle and a harmonic series representation of the periodic load torque, obtaining a speed error by subtracting the angular speed from a reference angular speed, determining a DC component of the periodic load torque based at least in part on a speed error and a closed loop feedback control algorithm, calculating an electromagnetic torque using the DC component of the periodic load torque and the amplitude of the fundamental harmonic of the periodic load torque, and operating the electric motor to generate the calculated electromagnetic torque on the rotor.

A fluid pump includes a motor disposed within an outer housing. The motor includes a stator and a rotor in electromagnetic communication with the stator. Windings are disposed on the stator that receive an electric current for defining the electromagnetic communication. A pump element is attached to the rotor via a drive shaft. The pump element operates with the rotor to deliver a fluid through a hydraulic fluid path. A plurality of sensors measure information related to at least one of the stator, the windings, the rotor, the pump element, the fluid and the hydraulic fluid path. A controller is in communication with the windings for delivering the electric current to the windings. The controller is also in communication with the plurality of sensors for measuring and recording the information and communicating this information to one of an external memory and an external controller.

A method of operating a compressor includes obtaining a mechanical angle and an angular speed of a rotor, determining an amplitude of a fundamental harmonic of a periodic load torque exerted on the rotor based at least in part on the mechanical angle and a harmonic series representation of the periodic load torque, obtaining a speed error by subtracting the angular speed from a reference angular speed, determining a DC component of the periodic load torque based at least in part on a speed error and a closed loop feedback control algorithm, calculating an electromagnetic torque using the DC component of the periodic load torque and the amplitude of the fundamental harmonic of the periodic load torque, and operating the electric motor to generate the calculated electromagnetic torque on the rotor.

A fluid pump includes a motor disposed within an outer housing. The motor includes a stator and a rotor in electromagnetic communication with the stator. Windings are disposed on the stator that receive an electric current for defining the electromagnetic communication. A pump element is attached to the rotor via a drive shaft. The pump element operates with the rotor to deliver a fluid through a hydraulic fluid path. A plurality of sensors measure information related to at least one of the stator, the windings, the rotor, the pump element, the fluid and the hydraulic fluid path. A controller is in communication with the windings for delivering the electric current to the windings. The controller is also in communication with the plurality of sensors for measuring and recording the information and communicating this information to one of an external memory and an external controller.

A fluid pump includes a motor disposed within an outer housing. The motor includes a stator and a rotor in electromagnetic communication with the stator. Windings are disposed on the stator that receive an electric current for defining the electromagnetic communication. A pump element is attached to the rotor via a drive shaft. The pump element operates with the rotor to deliver a fluid through a hydraulic fluid path. A plurality of sensors measure information related to at least one of the stator, the windings, the rotor, the pump element, the fluid and the hydraulic fluid path. A controller is in communication with the windings for delivering the electric current to the windings. The controller is also in communication with the plurality of sensors for measuring and recording the information and communicating this information to one of an external memory and an external controller.