A solvent supply system for supplying a composite solvent is described. The solvent supply system comprises a first supply flow path with a first pump unit, the first supply flow path being adapted for supplying a flow of a first solvent to a mixing unit, the first pump unit operating periodically, and a second supply flow path with a second pump unit, the second supply flow path being adapted for supplying a flow of a second solvent to the mixing unit, the second pump unit operating periodically. The mixing unit is adapted for mixing the first and the second solvent and for supplying a composite solvent. The solvent supply system further comprises a control unit adapted for controlling operation of the first and the second pump unit, the control unit being adapted to prevent at least one of a predefined phase relation and a predefined frequency relation between the first pump unit and the second pump unit.

A system and method for a compressor includes a compressor connected to a condenser, a discharge line temperature sensor that outputs a discharge line temperature signal corresponding to a discharge line temperature of refrigerant leaving the compressor, and a control module connected to the discharge line temperature sensor. The control module determines a saturated condenser temperature, calculates a discharge superheat temperature based on the saturated condenser temperature and the discharge line temperature, and monitors a flood back condition of the compressor by comparing the discharge superheat temperature with a predetermined threshold. The control module increases a speed of the compressor when the discharge superheat temperature is less than or equal to the predetermined threshold.

A pump control device includes: a current detection unit detecting a current value of current flowing through a coil of a motor driving an electric pump; a determination unit determining whether a determination condition in which the detected current value is equal to or larger than a preset value and the current value equal to or larger than the preset value continues for a preset time or more is satisfied; an inverter including three arm units having high-side and low-side switching elements connected to each other in series between first and second power supply lines; and an energization control unit driving the high-side and low-side switching elements by PWM control, and perform the PWM control by lowering a carrier frequency of a PWM signal by a predetermined frequency when the determination condition is satisfied.

The invention relates to a pump system comprising a positive-displacement pump module, preferably a screw pump, a drive module which can be exchanged separately from the positive-displacement pump module, said drive module comprises an electric drive motor and a frequency converter associated therewith for controlling or adjusting a drive motor speed, control means comprising a controller for producing an adjustment variable (Y.sub.S) for the frequency converter in accordance with a reference variable (W) and a first actual operational parameter (X) and logistic means associated with the controller, and reference variable defining means for providing the reference variable (W) for the control means. According to the invention, the control means are provided in a control module separately from the drive module, and the drive module can be exchanged separately from the control module, and the drive module does not have a designed and/or controlled controller for producing the adjustment variable (Y.sub.S).

In some implementations, a controller may obtain a setting for a maximum discharge pressure associated with a fluid pump that is to be allowed during a hydraulic fracturing operation. The fluid pump may be driven by a motor that is controlled by a variable frequency drive (VFD). The controller may determine a maximum torque for the motor that achieves the maximum discharge pressure. The controller may cause, via the VFD, adjustment to a speed of the motor to maintain a torque of the motor at or below the maximum torque for the motor.

An on-board fluid machine includes a housing configured to allow fluid to flow into the housing, an electric motor accommodated in the housing, and a driver that is supplied with DC power and drives the electric motor. The driver includes a low-pass filter circuit and an inverter circuit. The low-pass filter circuit includes a common mode choke coil and a capacitor. The driver further includes a damping unit located at a position where magnetic field lines produced by the common mode choke coil generate eddy current.

The invention relates to a pump system comprising a positive-displacement pump module, preferably a screw pump, a drive module which can be exchanged separately from the positive-displacement pump module, said drive module comprises an electric drive motor and a frequency converter associated therewith for controlling or adjusting a drive motor speed, control means comprising a controller for producing an adjustment variable (Y.sub.s) for the frequency converter in accordance with a reference variable (W) and a first actual operational parameter (X) and logistic means associated with the controller, and reference variable defining means for providing the reference variable (W) for the control means. According to the invention, the control means are provided in a control module separately from the drive module, and the drive module can be exchanged separately from the control module, and the drive module does not have a designed and/or controlled controller for producing the adjustment variable (Y.sub.s).

A method for operating a fluid delivery system, with a fluid delivery pump, voltage manipulator and an electric motor integrated into an electrical grid. The electric motor is controlled by a voltage applied to the electric motor and the voltage manipulator is upstream from the electric motor. The following steps include determining the desired fluid output, determining the required rotational speed of the pump to convey the desired fluid output, determining the required voltage to reach the required pump rotational speed, and activating the voltage manipulator to achieve the required voltage.

A control system and method of a VFD-based pump are disclosed. The control system controls an electric motor via a VFD, and the electric motor drives the pump. The control system comprises: an anti-ripple injection module for injecting an anti-ripple signal into a control path, the anti-ripple signal causing pressure ripples in the pump output to he at least partially cancelled. Further disclosed is a pump system, comprising: a VFD, an electric motor, and a pump, wherein the VFD comprises the control system stated above.

A power conversion circuit board (1) is a board on which a power conversion circuit which converts direct current to alternating current is mounted. A low voltage circuit (10b) to which a low voltage is applied and a high voltage circuit (10a) to which a high voltage is applied are separately disposed in different areas on the same board surface. Further, the high voltage circuit (10a) includes a bus bar in which a part of a wiring is formed on the board surface and another wiring is provided with a predetermined distance from the board surface.