A power converter including a compressor as a load includes a compensation current output (80) allowing compensation current (Ic), which compensates for leakage current (Ia), to flow. A controller (50) receives a detection signal from a rotational speed sensor (55) which senses the rotational speed of the compressor (CM). When the rotational speed has increased to a set rotational speed at which the leakage current (Ia) is lower than or equal to its limiting value (Lmax) (e.g., the limiting value specified under the Electrical Appliances and Materials Safety Act or by the IEC) in a state where the compensation current output (80) is off, the compensation current output (80) is switched from an on state to an off state. This may reduce the leakage current from the compressor with low power loss.

A malfunction diagnosing device that includes pistons arranged in a circumferential direction and discharges oil with rotation in the circumferential direction is provided, including: a pressure sensor for detecting a pressure value of oil discharged from a hydraulic pump in rotation; a speed sensor for detecting a rotation phase of the hydraulic pump at a time when a pressure value of oil is detected by the pressure sensor; a phase calculation part; and a rendering part for rendering a model of a relationship between pressure values of oil detected by the pressure sensor and rotation phases of the hydraulic pump detected by the speed sensor and the phase calculation part to thereby obtain pulsating waveform data. This makes it possible to diagnose a malfunction of the hydraulic pump without influence of a change in a rotation speed of the hydraulic pump.

Methods and systems for controlling a chiller system to achieve control stability while maintaining optimum efficiency. Particularly, methods and systems for controlling a centrifugal compressor speed and an inlet guide vane position that establishes three distinct regions in the control path: (i) during initial unloading from full load, the inlet guide vane position is kept at a fully open position while the centrifugal compressor speed is changed to achieve the desired cooling capacity; (ii) between an inflection point and a transition point, keeping the centrifugal compressor speed constant while the inlet guide vane position is changed to achieve the desired cooling capacity; and (iii) between the transition point and zero cooling capacity, changing both the inlet guide vane position and the centrifugal compressor speed to achieve the desired cooling capacity.

A method monitors the state of a device having a first drive cylinder for receiving hydraulic fluid and a first drive piston which is movably arranged in the first drive cylinder. The method determines a speed of the first drive piston, establishes a difference between the determined speed of the first drive piston and an expected speed of the first drive piston, and determines a faulty state as a function of the difference established between the determined speed of the first drive piston and the expected speed of the first drive piston.

The present disclosure describes a control method for a compressor system that comprises a compressor connected to a pressure vessel and a frequency converter controlling an electric motor of the compressor. In the method, the present operating state is estimated on the basis of a monitored/estimated electrical quantity of the compressor system. The operating state may represent the pressure in the pressure vessel. The pressure in the pressure vessel causes a counter-torque to the motor. The counter-torque is proportional to the pressure and may be used for estimating the pressure inside the pressure vessel. An estimate of a counter-torque may be calculated on the basis of the monitored electrical quantity or quantities.

An apparatus, method, and non-transitory computer readable recording medium to control a pump system may include a memory storing instructions and a processor that executes the instructions to obtain initial motor data of a motor controlled by a variable frequency drive (VFD) and determine a normal speed baseline of the motor based on the obtained initial motor data. The processor may also obtain current motor data of the motor, detect a pump-off event of the pump system when the current motor data deviates from the normal speed baseline, and control the VFD in response to the detected pump off event.

There is provided a technique that includes: a main controller configured to execute a process recipe including a plurality of steps to perform a predetermined process on a substrate so as to acquire device data when executing the process recipe; and a storage part configured to store the acquired device data, wherein the main controller is configured to: acquire the device data in a predetermined specific step among the steps constituting the process recipe; calculate a value of the acquired device data in the specific step; compare the calculated value with a value of the device data in the specific step calculated at a time of previous execution of the process recipe; and generate an alarm when the calculated value shows a predefined tendency.

Systems and methods to pump fracturing fluid into a wellhead may include a gas turbine engine including a compressor turbine shaft connected to a compressor, and a power turbine output shaft connected to a power turbine. The compressor turbine shaft and the power turbine output shaft may be rotatable at different rotational speeds. The systems may also include a transmission including a transmission input shaft connected to the power turbine output shaft and a transmission output shaft connected to a hydraulic fracturing pump. The systems may also include a fracturing unit controller configured to control one or more of the rotational speeds of the compressor turbine shaft, the power turbine output shaft, or the transmission output shaft based at least in part on target signals and fluid flow signals indicative of one or more of pressure or flow rate associated with fracturing fluid pumped into the wellhead.

Systems and methods to pump fracturing fluid into a wellhead may include a gas turbine engine including a compressor turbine shaft connected to a compressor, and a power turbine output shaft connected to a power turbine. The compressor turbine shaft and the power turbine output shaft may be rotatable at different rotational speeds. The systems may also include a transmission including a transmission input shaft connected to the power turbine output shaft and a transmission output shaft connected to a hydraulic fracturing pump. The systems may also include a fracturing unit controller configured to control one or more of the rotational speeds of the compressor turbine shaft, the power turbine output shaft, or the transmission output shaft based at least in part on target signals and fluid flow signals indicative of one or more of pressure or flow rate associated with fracturing fluid pumped into the wellhead.

An inclined-axis axial piston machine includes a housing, a drive shaft and a cylinder barrel. The drive shaft is mounted in the housing so as to be rotatable with respect to a first axis of rotation and is integral with a flange. Each piston is coupled to the flange via a ball joint. A multiplicity of counting perforations are arranged in a periodically distributed and continuous manner over an outer circumferential surface of the flange. The housing accommodates a sensor arranged opposite the counting perforations such that rotation of the drive shaft causes a signal change at the sensor. Each counting perforation is formed integrally from the flange, in the form of a recess having a single continuous perimeter. A side wall of the recess, starting from the perimeter, extends uninterruptedly, without sharp bends or offsets, over the entire circumference of the perimeter.