A screw compressor (100), comprising a screw rotor (110) and a spool valve (120). The screw rotor (110) comprises a suction head end (111) and an exhaust tail end (112). Gas is sucked in from the suction head end (111) and compressed gas is discharged from the exhaust tail end (112). The spool valve (120) comprises a working side (125) for sealing a compression chamber of the screw rotor (110). The working side (125) comprises a spool valve head end (121) and a spool valve tail end (122) and can do a reciprocating motion along the axis direction of the screw rotor (110). When the spool valve (120) moves to a suction capacity adjusting position (240), the spool valve head end (121) is located at the inner side of the suction head end (111) of the screw rotor (110), and a suction capacity adjusting distance (D2) is formed between the spool valve head end (121) and the suction head end (111) so that the suction capacity of the screw compressor is adjusted. The suction capacity of the screw compressor (100) can be adjusted by means of the spool valve (120), so that the problem of motor temperature and exhaust gas temperature limits of conventional variable frequency screw sets is effectively solved and the operational range and the load regulation ability of the screw compressor are expanded.

The control section controls the electric motor to be driven such that the number of revolutions becomes equal to the target number of revolutions. If the control section sets the target number of revolutions to a number of revolutions of the electric motor requested by another control section, the control section changes the number of revolutions of the electric motor at an increase rate lower than or equal to the upper limit value of the increase rate or at a decrease rate lower than or equal to the upper limit value of the decrease rate. If the control section sets the target number of revolutions to a number-of-revolutions limit value, which is determined based on the voltage of a vehicle battery, the control section is able to decrease the number of revolutions of the electric motor at a decrease rate exceeding the upper limit value.

An in-vehicle motor-driven compressor includes a temperature rise estimator configured to estimate a temperature rise of the diode based on an expected reverse current, an on-voltage of the diode, and a heat resistance of the diode. The in-vehicle motor-driven compressor further includes a rotation speed controller configured to set a rotation speed limit of the electric motor, based on the estimated temperature rise of the diode so that a temperature of the diode does not exceed a junction temperature of the diode even when the electric motor is stopped and the reverse current flows through the diode, and limit a rotation speed of the electric motor to lower than or equal to the rotation speed limit.

An improved progressing cavity pump, methods of making the same, methods of using the same, and methods of retrofitting conventional progressing cavity pumps are disclosed. The improved progressing cavity pump has an improved polished rod, which is connectable to a slider tool, that enables the rod string, including the pump's rotor to be lowered in the production tubing without requiring disassembly of the above ground equipment. Preferably, the slider tool functions to extend the length of the improved polished rod, and the connection between the slider tool and the improved polished rod is preferably configured to ensure that the outside diameter of the connection is no larger than the passageways of the above ground equipment it needs to pass through, when it is lowered. Also disclosed is an improved polished rod clamp. An indicator which enables an operator on the ground to visually determine whether a progressing cavity pump is operating, or whether it is operating correctly is also disclosed.

When the magnitude of a motor current Iu is smaller than a threshold value at a timing when a polarity of the motor current Iu is expected to be reversed after the elapse of one control cycle, a control device sets a correction amount of a width of a pulse generated by PWM control at a correction amount +. When the magnitude of the motor current is greater than the threshold value at the timing, the control device sets the correction amount of the width of the pulse generated by the PWM control at zero or a value smaller than the correction amount +. As a result, an error of a dead time period in inverter control can be reduced.

A fluid-driven actuator system includes a fluid-driven actuator and at least one proportional control valve and at least one pump connected to the fluid-driven actuator to provide fluid to operate the fluid-driven actuator. The at least one pump includes at least one fluid driver having a prime mover and a fluid displacement assembly to be driven by the prime mover such that fluid is transferred from the pump inlet to the pump outlet. The fluid driven actuator system also includes a controller that establishes at least one of a speed and a torque of the at least one prime mover to adjust at least one of a flow in the fluid system to a flow set point and a pressure in the fluid system to pressure set point and a concurrently establishes an opening of the at least one proportional control valve to adjust at least one of the flow to the flow set point and the pressure to the pressure set point.

A method of operating a rolling piston compressor includes determining a pressure difference (?P) between a discharge pressure (P.sub.d) within a compression volume and a suction pressure (P.sub.s) within a suction volume; determining a pressure ratio (r.sub.p) equal to the discharge pressure (P.sub.d) over the suction pressure (P.sub.s); estimating a discharge pressure (P.sub.d) based at least in part on the pressure difference (?P) and the pressure ratio (r.sub.p); determining that the discharge pressure (P.sub.d) is greater than a predetermined pressure limit (P.sub.d-limit); and lowering a target speed (?.sub.target) of the rolling piston compressor.

A rotary-vane internal combustion engine of the cat and mouse or scissor type with coordinated rotation of two co-axial shafts with position sensors creating chambers of variable volume for intake, compression, power and exhaust strokes. A reversible electric generator motor on at least one of the shafts with an electronic control system for current, an energy storage unit and electrical load. The total work done and angular speed is calculated or empirically determined while an alternating accelerating or decelerating torque is applied for a continuous, uniform rotation cycle.

An electric compressor includes a housing, refrigerant inlet port, a refrigerant outlet port, an inverter section, a motor section, a compression device and a front cover. The housing defines an intake volume and a discharge volume. The refrigerant inlet port is coupled to the housing and is configured to introduce the refrigerant to the intake volume. The compression device is a scroll-type compression device configured to compress the refrigerant. The refrigerant outlet port is coupled to the housing and is configured to allow compressed refrigerant to exit the scroll-type electric compressor from the discharge volume. The electric compressor includes integral pressure(s) and/or temperatures sensor(s).

When the magnitude of a motor current Iu is smaller than a threshold value at a timing when a polarity of the motor current Iu is expected to be reversed after the elapse of one control cycle, a control device sets a correction amount of a width of a pulse generated by PWM control at a correction amount +. When the magnitude of the motor current is greater than the threshold value at the timing, the control device sets the correction amount of the width of the pulse generated by the PWM control at zero or a value smaller than the correction amount +. As a result, an error of a dead time period in inverter control can be reduced.