Abstract: A cooling system including redundant fan controllers. The cooling system includes a first fan controller coupled to control a first plurality of fans and a second fan controller coupled to control a second plurality of fans. During operation, the first plurality of fans and the second plurality of fans operate concurrently. The first fan controller and the second fan controller are each configured to monitor the first and the second plurality of fans and to detect a failure in any of the first and the second plurality of fans. Further, in response to detecting a failure of a fan of the first plurality of fans, the second fan controller is configured to increase an operating speed of a corresponding fan of the second plurality of fans.

Abstract: In an apparatus and a method for controlling operation of a compressor, by removing deviation generated by resistance and inductance and removing an error in a stroke estimation value of a compressor, operation of the compressor can be accurately controlled. The apparatus includes a counter electromotive force detector for detecting a counter electromotive force generated at a motor of a compressor. A stroke calculator calculates a stroke estimation value of the compressor on the basis of the counter electromotive force, and a stroke controller controls a stroke of the compressor by varying a voltage applied to the motor on the basis of the calculated stroke estimation value and a stroke reference value.

Abstract: A control method for an electric pump adapted to supply pressurised operating fluid to actuators of an automatic transmission in order to cause the opening/closing of the clutch and the selection and engagement of the gears, in which the stage of supply of a voltage to the motor of the electric pump is carried out in order to cause the electric pump to rotate. The method comprises the stage of regulating the supply voltage as a function of actual operating conditions monitored in the vehicle using the automatic transmission.

Abstract: When an electric compressor is activated, initial current data is selected by a selector, and a motor is driven with the torque corresponding to the initial current data. When the motor is driven by a ½ turn, the selector selects current difference data. The current difference data corresponds to an instructed speed. After the switch of the selector, the motor is driven to rotate at the instructed speed.

Abstract: The present invention provides an improved design of linear motor as well as an improved control strategy. The design allows for a shorted stator, where the armature magnets are controlled to reciprocate to a greater maximum displacement that for a equivalent conventional linear motor. The control strategy is such that a minimum of external sensors are required. The linear motor is driven at its resonant frequency ensuring optionally efficient operation. A determination of the maximum current is made based on a relationship with the resonant frequency and the evaporating temperature/pressure of the vapor entering the compressor. The current is then limited to control the maximum displacement to avoid damage.

Abstract: Device and method for controlling a piston position in a linear compressor, having a power source, a triac, and a motor, the device including a current phase detecting part for detecting a current switched at the triac, integrating the current, and generating a first square wave corresponding to the integrated current, a stroke phase detecting part for generating an AC voltage waveform having a fixed frequency and varied amplitude according to a piston reciprocation position following motor operation, and generating a second square wave corresponding to the AC voltage waveform, a zero cross detecting part for detecting a zero crossing of the voltage supplied from the power source, and a controlling part for generating a signal for controlling a piston position according to a phase difference of the first square wave detected at the current phase detecting part and the second square wave detected at the stroke phase detecting part, thereby making an efficiency and a reliability the best by controlling a piston

Abstract: In a stroke control apparatus of a reciprocating compressor and a method thereof, the stroke control apparatus of the reciprocating compressor includes a reciprocating compressor, a current detecting unit for detecting a current flowing in a motor of the reciprocating compressor, a stroke detecting unit for detecting a piston stroke by using a voltage and a current applied to the motor of the reciprocating compressor, a phase difference detecting unit for detecting a phase difference by receiving the piston stroke from the stroke detecting unit and the motor current from the current detecting unit, an operational frequency determining unit for determining an operational frequency corresponded to an operation region according to the detected phase difference, a frequency/stroke storing unit for storing a piston stroke value by the determined operational frequency, a reference stroke value determining unit for determining a reference stroke value corresponded to the determined operational frequency by using the

Abstract: A centrifugal fluid pump apparatus includes a control mechanism; and a body 5 including a pump section having an impeller rotating inside a housing; a rotor having an impeller attraction magnet; a motor for rotating the rotor; an impeller attraction electromagnet for attracting the impeller thereto; an impeller-position detection sensor; and a groove for hydrodynamic bearing provided on an inner surface of the housing. The control mechanism has a position sensor output monitoring function or an electromagnet current monitoring function, a motor current monitoring function; and an emergency impeller rotation function. The impeller rotation function operates when the sensors or the electromagnet has a failure by using the position sensor output monitoring function or the electromagnet current monitoring function to rotate the impeller by utilizing the groove for hydrodynamic bearing.

Abstract: In a driving apparatus of a linear compressor 1 having a power source capable of controlling output current and measuring output electric power, frequency of the linear compressor 1 is controlled such that the amplitude of current which is supplied to the linear compressor 1 is made constant and electric power which is supplied to the linear compressor 1 becomes maximum. With this, it is possible to drive the linear compressor 1 efficiently while following the resonance frequency which keeps varying with variation of a load. Further, a current detecting means 8 capable of detecting output current and electric power from inverter input current is provided, and it is unnecessary to newly add a current sensor.

Abstract: An apparatus and a method are disclosed for controlling operation of a compressor capable of greatly decreasing a stroke estimation error of a compressor and controlling operation of the compressor accurately and precisely. The method includes calculating a first stroke estimation value of a compressor on the basis of current, a voltage applied to a motor of a compressor and preset parameters of the motor. Detecting a counter electromotive force of the motor and calculating a second stroke estimation value of the compressor on the basis of the detected counter electromotive force value.

Abstract: An apparatus and method of controlling a linear compressor. The apparatus includes a current detection unit to detect current, a control unit to determine whether a collision between a piston and a valve occurs, and controlling a stroke of the linear compressor, and a compressor drive unit to perform adjustment of the stroke of the linear compressor. The method includes presetting a maximum stroke and a collision point according to a load, selectively increasing and reducing a stroke of the linear compressor according to a variation in the load, and controlling the stroke.

Abstract: An active sensing and switching device for use in controlling current to a load, comprising a controller means (U1) for disconnecting the load from a power source by providing a switch-open control signal based on a signal indicating a sensed value of electrical current to the load, characterized in that the controller means (U1) determines a nominal value for the electrical current to the load based on monitoring the signal indicating the sensed value of electrical current to the load. A load control system is also provided, including a single ASSD adapted to receive signals indicating sensed values of electrical current to a plurality of respective loads, and further comprising a plurality of load control modules adapted so as to be disposed in proximity to respective loads or a main power line, wherein the load control modules provide respective signals indicating sensed values of electrical currents to the respective loads.

Abstract: Disclosed is an apparatus for controlling a driving of a reciprocating compressor and a method thereof, in which a cooling capacity is decreased without a re-expansion loss by controlling a driving of a compressor used in a refrigerator by using a current offset when the cooling capacity of a refrigerator is varied.

Abstract: A power fan speed controller is capable of adjusting a fan speed synchronously along with the variation of a load power so as to solve the shortcomings of a conventional, unsteady, not precise enough and temperature-controlled fan speed controller. The structure of the present invention detects a power signal at the power source end and converts the power signal into a voltage signal in direct ratio to the power; the voltage signal is transmitted into a comparator to compare with a reference voltage thereby controlling a transistor connected with the fan.

Abstract: A linear compressor driving apparatus having an inverter which supplies a driving current of a predetermined frequency to a linear compressor. The linear compressor driving apparatus further includes an inverter controller for controlling the inverter on the basis of resonance frequency information so that the frequency of an output current from the inverter becomes equal to the resonance frequency, and instantaneous values of an output current and an output voltage from the inverter are measured at a phase timing in which an amount of change in the output current of the inverter becomes zero. A piston stroke is calculated from these measured values. In such a linear compressor driving apparatus, a stroke and a top clearance of the piston of the linear compressor can be accurately detected by relatively simple arithmetic processing without using a position sensor.

Abstract: Aspects for integrating speed control and fault detection in a fan assembly are described. The aspects include a fan, a first circuit is coupled to the fan for regulating speed of the fan, and a second circuit coupled to the fan and to the first circuit for detecting a fault condition in the fan. A ripple regulator is integrated as the first circuit, and a pulse missing detector circuit is integrated as the second circuit.

Abstract: An operation control method of a reciprocating compressor is disclosed in which, in case that a motor is overloaded, an operation frequency is increased to render magnetic fluxes of a magnet and an input current are mutually offset, so that a reciprocating compressor can be stably driven even in case of the overload. For this purpose, while the reciprocating compressor using an inverter is operated at a rated frequency, a current load of the motor is measured and the measured load is compared with a pre-set reference load. Upon comparison, if the measured load is greater than the reference load, it is determined as an overload and the operation frequency is increased by as much as a certain value higher than an oscillation frequency, for performing an overload operation.

Abstract: A control apparatus for a linear compressor driving system is disclosed for stabilizing the behavior of a piston and thereby protecting the increase in noise vibration caused by collision and the reduction in reliability. This control apparatus stabilizes the behavior of the piston by including: an unstableness detecting means, which directly or indirectly detects that the behavior of the piston is unstable and then outputs an unstableness detection signal; and an unstableness avoiding means which is operated in accordance with the unstableness detection signal.

Abstract: A method for the operation of a centrifugal pump (2) driven by an electric motor (5) with variable frequency, wherein too small a flow through the pump (2) is ascertained by monitoring electrical quantities, and a pump arrangement (1) having a centrifugal pump (2), an electric motor (5) which drives the centrifugal pump (2), a controlled frequency converter (6) which feeds the electric motor (5), a sensor device (12, 13) and an evaluating device (15-19) are described. It is desired to detect, by simple means, when no through-flow is present. For that purpose, the electrical power is ascertained and compared to a control quantity formed as a function of the frequency of the motor (5). The sensor device ascertains values for determination of the electrical power, and the evaluating device has a dynamic limit value former (18), which forms a control quantity as a function of the frequency of the motor (5).

Abstract: A control system for the operation of a progressing cavity pump which may be used for production of gas and/or oil from a well. The control system includes vector feedback model to derive values of torque and speed from signals indicative of instantaneous current and voltage drawn by the pump motor, a pump model which derives values of the fluid flow rate and the head pressure for the pump from torque and speed inputs, a pumping system model that derives from the estimated values of the pump operating parameters an estimated value of a pumping system parameter and controllers responsive to the estimated values of the pumping system parameters to control the pump to maintain fluid level at the pump input near an optimum level.

Abstract: A rod pump control system includes a parameter estimator that determines from motor data parameters relating to operation of the rod pump and/or downhole dynamometer card without the need for external instrumentation, such as down hole sensors, rod load sensors, flow sensors, acoustic fluid level sensors, etc. In one embodiment, instantaneous motor current and voltage together with pump parameters are used in determining rod position and load. The rod position and load are used to control the operation of the rod pump to optimize the operation of the pump. Also disclosed in a pump stroke amplifier that is capable of increasing pump stroke without changing the overall pumping speed, or in the alternative, maintaining the well output with decreased overall pumping speed.

Abstract: The present invention is directed to a centrifugal pump wherein voltage and current data are detected from voltage and current sensors in the pump motor. A power signal is then generated from the voltage and current data and spectrally analyzed to determine the low flow or cavitation in the pump. As such, unwanted operational conditions resulting from improper pump operation may be detected and a warning or maintenance flag provided without additional transducers and other instruments on the motor or pump.

Abstract: An air conditioning system for a vehicle that is driven by a vehicular power source. The system has a compressor selectively operable by the vehicular power source and an electric motor. The electric motor is used as a drive force of the compressor when the vehicular power source is in a non-operative state. The compressor compresses refrigerant gas introduced into a suction chamber from an external refrigerant circuit. A displacement of the compressor is variable, based on a differential pressure. The compressor has a control valve that is disposed on a refrigerant passage communicating with the crank chamber. The control valve has a valve plunger for changing an opening size of the control valve to adjust pressure in the crank chamber. The air conditioning system comprises pressure sensing member, actuator, and controller. The pressure sensing member is disposed in the control valve and applies biasing force to the plunger based on pressure in the external circuit.

Abstract: An apparatus controlling an output of a linear compressor having a stator and a rotor includes a plurality of coil taps which are connected to a coil of the stator, a switching part which controls an intensity of a current flowing through the coil by being selectively connected to the plurality of coil taps, and a controller which controls the switching part to be selectively connected to the plurality of coil taps. The apparatus prevents a power factor of power provided to the coil from being decreased, increases the efficiency of the power and minimizes a copper loss and/or a iron loss on the coil.

Abstract: A low-noise electric structure of an electric power steering device for automotive vehicles is provided which includes a controller including a substrate on which drive devices working to drive an electric motor are installed. The drive devices, power supply terminal joints, and motor terminal joints are concentrated on a portion of the substrate, thereby permitting a path of current flowing from the power supply terminal joints to the motor terminal joints to be shortened. This results in a decrease in quantity of heat generated from a circuit line extending between the power supply terminal joints and the motor terminal joints.

Abstract: In an operation control apparatus of a compressor, a current, a voltage an d a TDC, etc. applied to a compressor are detected, a speed and a TDC are constantly controlled so as to place an operation point of the compressor within a high efficiency operation region by using a phase difference between each detected values (for example, a phase difference between the current and the voltage), and an operation frequency is varied according to a load variation, accordingly an operation efficiency of the compressor can be improved.

Abstract: An apparatus and method for operational control of a reciprocating motor compressor, includes performing an operation of the reciprocating motor compressor precisely and accurately. In addition, with the above apparatus and method, the phase difference between a first speed value of the motor (or first TDC value) and current applied to the motor is detected, the second speed value of the motor at the inflection point of the detected phase value (or second TDC value) is detected and stored as a reference value, and the speed of the motor is controlled on the basis of the reference value and the first speed value of the motor (or the first TDC value).

Abstract: When a hybrid compressor starts being driven by an electric motor, an electric current of a capacity control valve is applied at an initial control electric current SS that is greater than a control electric current S obtained from a state of a refrigerating cycle. This triggers a swash plate of the hybrid compressor to be rapidly inclined. Thereafter, the electric current of the displacement control valve is applied at the control electric current S. This structure enables a displacement of the hybrid compressor to be rapidly recovered when the hybrid compressor starts being driven by the electric motor.

Abstract: A method and apparatus for a pump and a pump control system. The apparatus includes pistons integrally formed in a diaphragm and coupled to the diaphragm by convolutes. The convolutes have a bottom surface angled with respect to a top surface of the pistons. The apparatus also includes an outlet port positioned tangentially with respect to the perimeter of an outlet chamber. The apparatus further includes a non-mechanical pressure sensor and a temperature sensor coupled to a pump control system. For the method of the invention, the microcontroller provides a pulse-width modulation control signal to an output power stage in order to selectively control the power provided to the pump. The control signal is based on the pressure within the pump, the current being provided to the pump, the voltage level of the battery, and the temperature of the pump.

Abstract: A driving apparatus of a linear motor which reciprocally drives a movable element supported by an elastic member, includes an inverter that converts a direct current power into an alternating-current power with a specified frequency to drive the linear motor, a current detector that detects the output current of the inverter, a voltage detector that detects the output voltage of the inverter, an amplitude detector that detects an amplitude of the movable element of the linear motor, an amplitude controller adjusts the output current or output voltage in a first control cycle so that the amplitude of the movable element is a desired constant value, and a resonant controller that adjusts the output frequency of the inverter in a second control cycle which is larger than the first control cycle so that the output current of the inverter is substantially minimum on condition that the amplitude is substantially constant.

Abstract: A system and method for controlling a compressor (1) is provided that prevents the piston (5) of the compressor from colliding against the valve system (8, 9) provided therein. The system and method of the present invention control the stroke of the piston (5), allowing the piston (5) to advance as far as the end of its mechanical stroke in extreme conditions of load, without allowing the piston (5) to collide with the valve system (8,9). The present invention controls the compressor (1) by measuring a movement time of the piston (5); comparing the movement time with a foreseen movement time; and altering the voltage (Vm) if the first movement time is different from the foreseen movement time, the foreseen movement time being such that the movement of the piston (5) will reach a maximum point (M).

Abstract: A centrifugal fluid pump assembly includes a body section and a control mechanism 6. The body section includes a housing, an impeller rotatable within the housing, and a motor for rotating the impeller. The pump assembly includes a motor current flow rate-related data storage section for storing, for a plurality of different predetermined viscosities, predetermined viscosity-related flow rate data formed from a plurality of motor current flow rate relation data at a plurality of different impeller rotational speeds at predetermined fluid viscosity; a fluid measurement data inputting section, an impeller rotational speed measurement function, a motor current measurement function, and a flow rate calculating section 58 for using a fluid viscosity value, an impeller rotational speed value, a measured motor current and data stored in the motor current flow rate-related data storage section to calculate a fluid flow rate.

Abstract: A high-pressure, dome-type compressor includes a DC motor 5 having a rotor 5a that uses a rare earth/iron/boron permanent magnet having an intrinsic coercive force of 1.7 MA.m−1 or greater in a rotor thereof and has a rated output or 1.9 kW or higher. The motor, which drives a compression element 3 in a casing 2, is disposed in a high pressure, high temperature area 6, which is filled with gas discharged from the compression element. An inverter 10 controls current supplied to the motor such that the motor temperature becomes equal to or less than a predetermined temperature and an opposing magnetic field generated in a stator has a predetermined strength or less. Since the magnet does not reach a high temperature and is not exposed to a strong opposing magnetic field, it is hardly demagnetized. As a result, performance of the motor and of the compressor is stable.

Abstract: Disclosure is made of a precision hydraulic energy delivery system that directly couples the pump to a primary mover (motor) and a related motor control. The system provides flow control of a hydraulically driven machine without the use of downstream devices by employing motion control algorithms in the motor control. Control features are electronically integrated into the hydraulic system by using control algorithms and subroutines specifically developed for the prime mover servo control system coupled to the pump.

Abstract: This invention relates to a mechanical oil recovery method and system with a sucker-rod pump. The method calculates the lowest power loss or the lowest cost. The method comprises sequentially arranging internal diameter, steel grade of rod, pump diameter, pumping depth and stroke amplitude, searching the combinations of rods to calculate pump efficiency and the number of strokes, on the basis of Pinput=Pactive−Pexpansion+Ploss, and calculating, corresponding to the input power Pinput, active power Pactive, expansion power Ppeng, ground power loss Pd, sliding power loss Ph and viscose power loss Pv and the sum of losses Ploss. The mechanical oil-recovering cost is then calculated for each combination, and each mechanical oil-recovering parameter is chosen.

Abstract: A system and methods for automatically adjusting pump operating parameters for at least one pump to accommodate solids encountered during a pumping operation. The output signal of a level sensor may be monitored so as to detect and account for variations therein. The power draw of the pump may also be monitored so as to detect and account for the presence of solids.

Abstract: A pump assembly that has a control circuit and a pressure switch which control the operation of a pump motor. The motor drives a positive displacement pump that is coupled to a fluid system. The control circuit includes a pulse width modulator circuit. The control circuit is activated when a pressure switch senses that a line pressure of the fluid system is below a threshold value. The control circuit can either operate in a continuous mode to provide a constant signal to the motor, or a pulse regulating mode to provide a series of pulses to the motor. The pulses begin with a minimum width and gradually increase until a predetermined current limit has been attained, or the motor reaches a full speed with the control circuit in a continuous on state. The speed of the motor will then correspond to the flow demanded by the fluid system. The energy provided by the pulses is varied as a function of changes in peak current drawn by the motor. The peak current is sensed and used to determine the pulse width.

Abstract: A control method for an electric pump adapted to supply pressurised operating fluid to actuators of an automatic transmission in order to cause the opening/closing of the clutch and the selection and engagement of the gears, in which the stage of supply of a voltage to the motor of the electric pump is carried out in order to cause the electric pump to rotate. The method comprises the stage of regulating the supply voltage as a function of actual operating conditions monitored in the vehicle using the automatic transmission.

Abstract: Disclosed is an apparatus and method for controlling a reciprocating compressor capable of inexpensively and exactly controlling a position of a piston in a cylinder, by which a top clearance is minimized according to the information of a phase difference between a square wave of a piston stroke and a square wave of a current supplied to the compressor. The apparatus comprises a driving section for driving the reciprocating compressor by varying an angle or ignition in response to a control signal; a current phase detecting section for outputting a square wave corresponding to the detected current supplied to the compressor; a stroke phase detecting section for outputting a square wave corresponding to a stroke of the compressor; and a control section for controlling the angle of ignition of the driving section according to the phase difference between the square wave produced from the current phase detecting section and the square wave produced from the stroke phase detecting section.

Abstract: An apparatus and a method for controlling operation of a linear motor compressor, by which a linear motor compressor can operate always in an optimum condition by coping with the load variation due to changes in a refrigerator and the circumstances. In more detail, a current peak value at TDC=0 is detected by comparing a current applied to the linear motor compressor with a formerly detected current, and accordingly the linear motor compressor is operated by a switching control signal generated according to a duty-ratio corresponding to the current peak value.

Abstract: An operation control method of a reciprocating compressor is disclosed in which, in case that a motor is overloaded, an operation frequency is increased to render magnetic fluxes of a magnet and an input current are mutually offset, so that a reciprocating compressor can be stably driven even in case of the overload. For this purpose, while the reciprocating compressor using an inverter is operated at a rated frequency, a current load of the motor is measured and the measured load is compared with a pre-set reference load. Upon comparison, if the measured load is greater than the reference load, it is determined as an overload and the operation frequency is increased by as much as a certain value higher than an oscillation frequency, for performing an overload operation.

Abstract: The invention relates to a fan arrangement comprising a radial or diagonal fan (370) with which a direct current motor (32) is associated as drive motor, further comprising a digital control element (23, 24) such as a microcontroller or microprocessor, associated with that direct current motor (32), and comprising a program, associated with that digital control element (23, 24), for controlling the current flowing through the direct current motor (32), which program is embodied to generate a substantially constant current in the motor (32) in the working rotation speed range of the fan.

Abstract: A reciprocating electromagnetic pump comprising a coil wound about a bipolar or tripolar core, a diaphragm structure mechanically coupled to at least one arm with a magnet attached to one end of the arm and a controller electronically connected to the coil. The controller comprises a pulse generator, a solid state switch that interrupts current flow through the pump electromagnet and additional electronic circuitry for signal processing. The arm is vibrated under the influence of a periodic electromagnetic field to produce the flow of gas. The flow of current through the electromagnet is interrupted so that the magnets are impelled during either a vacuum or a pressure stroke, but are not impelled during the reciprocal stroke. A signal produced in the electromagnet coil during the reciprocal is processed to provide feedback to control the pump drive frequency and phase to match the pump mechanical self-resonant frequency and phase under varying pumping loads.

Abstract: A driving controlling apparatus for reciprocating compressor using resonance, uses resonance increased in the current corresponding characteristic by compensating the inductance valve of a coil turned inner part of the motor using a capacitor. A electric circuit further comprises a capacitor for compensating the inductance of the coil which is wound around the motor of the reciprocating compressing unit, accordingly, the burden of the applied voltage against the inductance is reduced, so low applied voltage can generate the stroke needed and the variation of the current hardly effect to the variation of the stroke. Therefore, stable load characteristic is maintained because the stroke variation is low even if the load variation is generated.

Abstract: A pump off control method comprises detecting the speed of the induction motor and an instantaneous value of secondary current of the induction motor. Down stroke time in every cycle of the pump jack is detected. An average value of instantaneous values of the secondary current of the induction motor in the down stroke time in said every cycle is calculated. An average value reference of the secondary current of the induction motor to be compared with calculated average value of the instantaneous values of the secondary current of the induction motor is set. The calculated average value of the instantaneous values of the secondary current is compared with the average value reference after the down stroke end in each cycle. An occurence of pump off is detected if the calculated average value of the instantaneous values is greater than the average value reference.

Abstract: An air compressor control system is constructed to include a motor, an accumulation tank, a pump, a pressure switch, a pressure control valve, and a micro-controller. When the pressure of the accumulation tank surpassed a predetermined high level, the pressure switch is off, thereby causing the micro-controller to open the pressure control valve for relieving forced air pressure and then to turn off the motor. When the pressure of the accumulation tank dropped below the predetermined low level, the pressure switch is switched on, thereby causing the micro-controller to provide power supply to the motor again and then to close the air pressure control valve for enabling forced air to be pumped into the accumulation tank by the pump after the motor has been fully started.

Abstract: Disclosed is an apparatus for controlling a driving of a reciprocating compressor and a method thereof, in which a cooling capacity is decreased without a re-expansion loss by controlling a driving of a compressor used in a refrigerator by using a current offset when the cooling capacity of a refrigerator is varied.

Abstract: Device and method for controlling a piston position in a linear compressor, having a power source, a triac, and a motor, the device including a current phase detecting part for detecting a current switched at the triac, integrating the current, and generating a first square wave corresponding to the integrated current, a stroke phase detecting part for generating an AC voltage waveform having a fixed frequency and varied amplitude according to a piston reciprocation position following motor operation, and generating a second square wave corresponding to the AC voltage waveform, a zero cross detecting part for detecting a zero crossing of the voltage supplied from the power source, and a controlling part for generating a signal for controlling a piston position according to a phase difference of the first square wave detected at the current phase detecting part and the second square wave detected at the stroke phase detecting part, thereby making an efficiency and a reliability the best by controlling a piston

Abstract: A vacuum pump has an alternating current motor, a rotary shaft and a gas transferring body. The alternating current motor runs at a certain speed based on frequency of alternating current and is sufficiently supplied with the alternating current. Gas is transferred from a certain space by the gas transferring body driven by the alternating current motor through the rotary shaft. A method for controlling a vacuum pump includes keeping a rotational speed of the alternating current motor at a second predetermined rotational speed, detecting a value of the alternating current to the alternating current motor, keeping the rotational speed at a first predetermined rotational speed that is higher than the second predetermined rotational speed when the detected alternating current value exceeds a first predetermined value, and keeping the rotational speed at the second predetermined rotational speed when the detected alternating current value becomes equal to a second predetermined value.

Abstract: An overflow prevention mechanism for use in association with liquid transfer systems of the type including an electrically controllable flow control device such as a pump connected between a source of liquid and a liquid tank, the mechanism including a backup liquid level sensor and a shunt trip breaker or other normally-closed switching device. The backup liquid level sensor senses if the level of liquid within the tank reaches an extreme high level. When the liquid level within the tank reaches the extreme high level the backup liquid level sensor produces an output indicative of the liquid having reached such extreme high level. The shunt trip breaker is connected between the source of electrical energy and the flow control device.