Showing papers on "Variable-frequency drive published in 2009"

High capacity chiller compressor

Abstract: A high efficiency, low maintenance single stage or multi-stage centrifugal compressor assembly for large cooling installations. The assembly is highly efficient by virtue of a variable frequency drive (VFD) that drives a permanent magnet motor and matches compressor speed with compressor load, a direct drive impeller that eliminates gearing losses, and magnetic bearings that reduce frictional losses. The back-emf produced by the motor provides an intermediate power source for the magnetic bearings in the event of a loss of electrical power. A cooling system provides direct cooling of the rotor with gas refrigerant, and cooling of the stator with liquid refrigerant. Modular construction allows the compressor to be retrofit with upgrades. An inlet guide vane system operates without need for oil lubrication. The use of light metal castings and elimination of gearing reduces the weight to one-third or less of comparably powered conventional units.

High speed, high power electrical induction motor technologies for integrated compressors

Abstract: Since these last decades, Advances in high speed motor technology along with improvements in the cost and performance of variable frequency drive (VFD) and the emergence of active magnetic bearings (AMB) has allowed the development of an integrated motor-compressor, a gearless electrical motor directly coupled to a compressor, eliminating then the need for ancillary support systems, including the gearbox and the lube-oil system. The paper will describe the mechanical and the electrical design used for high speed, high power motors. A comparison of the performances will be detailed on four rotor designs.

Current Harmonics Analysis of Inverter-Fed Induction Motor Drive System under Fault Conditions

Abstract: This paper presents harmonic analysis of motor current signatures under different fault conditions of medium and high power Variable Frequency Drive (VFD) systems. Computer simulation of a VSI fed induction motor based on constant voltage/frequency (V/f) operation is implemented using Powersim (PSIM) simulation software. Frequency response characteristics of motor currents are compared to analyze fault conditions in motor drive system. dc bus. The dc bus contains capacitors to accept power from the rectifier, stores it, and later deliver that power through the inverter section. The inverter contains transistors that deliver power to the motor. The "Insulated Gate Bipolar Transistor" (IGBT) is a common choice in modern VFDs. The IGBT can switch on and off several thousand times per second and precisely control the power delivered to the motor. The IGBT uses "pulse width modulation" (PWM) technique to simulate a sine wave current at the desired frequency to the motor.

Safety System and Method for Pump and Motor

Abstract: Embodiments of the invention provide a variable frequency drive system and a method of controlling a pump driven by a motor with the pump in fluid communication with a fluid system. The drive system and method can provide one or more of the following: a sleep mode, pipe break detection, a line fill mode, an automatic start mode, dry run protection, an electromagnetic interference filter compatible with a ground fault circuit interrupter, two-wire and three-wire and three-phase motor compatibility, a simple start-up process, automatic password protection, a pump out mode, digital input/output terminals, and removable input and output power terminal blocks.

HVAC/R system with variable frequency drive (VFD) power supply for multiple motors

Abstract: An HVAC/R system is configured with a variable frequency drive power supply which provides power to each of a compressor, a condenser fan, and a blower. In some embodiments, the compressor has a three-phase motor and the condenser fan has a single-phase motor.

System and Method for Motor Drive Control Pad and Drive Terminals

Abstract: Embodiments of the invention provide a variable frequency drive system and a method of controlling a pump driven by a motor with the pump in fluid communication with a fluid system. The drive system and method can provide one or more of the following: a sleep mode, pipe break detection, a line fill mode, an automatic start mode, dry run protection, an electromagnetic interference filter compatible with a ground fault circuit interrupter, two-wire and three-wire and three-phase motor compatibility, a simple start-up process, automatic password protection, a pump out mode, digital input/output terminals, and removable input and output power terminal blocks.

Low stress soft charge circuit for diode front end variable frequency drive

Abstract: A variable frequency drive comprises a diode rectifier receiving multiphase AC power from a source and converting the AC power to DC power. An inverter receives DC power and converts the DC power to AC power to drive a load. A link circuit is connected between the diode rectifier and the inverter and comprises a DC bus to provide a relatively fixed DC voltage for the inverter. A bus capacitor is across the bus. A soft charge circuit limits inrush current to the bus capacitor. The soft charge circuit comprises an inductor connected between the source and the link circuit and a switch circuit in the link circuit for selectively providing a semiconverter configuration or a full bridge converter configuration to provide two stage charging of the bus capacitor.

Interleaved Discontinuous Space-Vector PWM for a multi-level PWM VSI using a 3-phase split-wound coupled inductor

Abstract: A multi-level interleaved Discontinuous Space Vector PWM (DSVPWM) method is presented for a 3-level 3-phase PWM VSI using a 3-phase split-wound coupled inductor. The selection of a suitable pwm switching scheme for this topology is based on the dual requirements for a high quality multi-level pwm output voltage together with the need to minimize high frequency currents and losses in the coupled inductor and the inverter switches. Suitable switching states are described for the DVSPWM over the entire range of amplitude modulation depth. This pwm scheme minimizes the coupled inductor high frequency winding current ripple and also produces 3-level pwm output voltage waveforms at twice the inverter switching frequency. The inverter operation is examined using simulation tests. Extensive experimental test results are used to obtain the inverter performance as a variable frequency drive when operated in steady-state and during transient conditions.

Hvac/r system with variable frequency drive power supply for three-phase and single-phase motors

Abstract: An HVAC/R system is configured with a variable frequency drive power supply which provides power to both a three-phase motor and to a single-phase motor. In some embodiments, the three-phase motor is a compressor motor and the single-phase motor is a condenser fan motor.

Variable frequency drive soft charge circuit

Abstract: A variable frequency drive comprises a diode rectifier receiving multiphase AC power and converting the AC power to DC power. An inverter receives DC power and converts the DC power to AC power to drive a load. A link circuit is connected between the diode rectifier and the inverter and comprises a DC bus to provide a relatively fixed DC voltage for the inverter. A link capacitor is across the bus. A soft charge circuit limits in rush current to the link capacitor. The soft charge circuit comprises an inductor in the bus and a resistor assist circuit across the inductor along with an anti-parallel clamping thyristor reverse connected also across the inductor.

System Having a Variable Frequency Power Distribution Bus for Driving a Variable Speed Motor

Abstract: A power distribution system is provided for supplying power to a variable speed motor for rotating a shaft. The system comprises a variable speed prime mover adapted to generate an A/C output having a variable frequency corresponding to the speed of the prime mover, a power switch, a power distribution bus connected to the A/C output of the prime mover and connected, via the switch, to the motor such that the motor's speed is varied relative to the frequency of the A/C output, and a variable frequency drive operatively connected to the A/C output of the prime mover via the bus and effective to provide an alternate A/C output to the motor after the motor is disconnected from the bus. The switch is adapted to disconnect the motor from the bus when the prime mover's speed is equal to or within a predetermined range of the prime mover's speed limit.

Induction motor loads and voltage stability assessment using PV curves

Abstract: Knowledge of the load composition and characteristics, such as corresponding PV curves, are necessary tools for the voltage stability analysis. This paper investigates small industrial induction motors that are operated under different mechanical load conditions. Experimental tests were performed to determine the system's PV characteristics and assess the voltage stability under different loading composition. The load characteristics of induction motor directly connected to the grid, as well as operated with a variable frequency drive (VFD) in open and closed loop speed control configurations were investigated experimentally. An equivalent exponential load model was identified for each configuration. The paper compares the constant power loads with the induction motor loads and shows that the VFD will have a pronounced effect on the load characteristic, which in turns affects the voltage stability.

MODELING a transistor converter-fed permanent magnet poly-phase machine and a variable-frequency drive controller under non-sinusoidal back-EMF conditions

Abstract: The paper presents a model of a poly-phase permanent magnet motor of the marine propulsion drive energized by multistage VSI. The model defines more precisely the non-sinusoidal waveform of back-EMF and its impact on the current distortion and electromagnetic torque ripples. The paper concludes by analyzing simulation results that have shown significant suppression of high order current harmonics and corresponding decrease in torque ripples due to the proposed control algorithm realized in a phase reference frame.

Bypass and Synchronous Transfer Arrangement for a Medium Voltage Drive Control System

Abstract: A medium voltage variable frequency drive having a 2-high controller configuration with a dual bus system is described. The drive control system includes at least one motor control cabinet housing a fused medium voltage bypass controller, a non-fused transfer controller positioned above the fused medium voltage bypass controller, an extendable output bus coupled to the non-fused medium voltage transfer controller, and an extendable supply bus coupled to the fused medium voltage bypass controller. The drive control system further includes a variable frequency drive cabinet housing a variable frequency drive. The variable frequency drive is coupled to the extendable output bus and a power supply line. The power supply line may be further coupled to the extendable supply bus. The drive control system includes at least one cabling transition cabinet housing cabling between the at least one motor control cabinet, the power supply line, and the variable frequency drive.

Drive control system of escalator or automatic footway

Abstract: The utility model discloses a driving control system of an escalator or a moving sidewalk. The driving control system comprises a power switch, a frequency changer, an operating contactor 1, an operating contactor 3, an overload protective relay and an electric motor which are connected in sequence through three conducting wires, wherein, the frequency changer is also connected with a PLC controller, and both ends of the frequency changer and the operating contactor 1 are connected in parallel with an uplink contactor and a downlink contactor which are connected in parallel as well; the electric motor is also connected with a Y-shaped operating contactor and a triangular operating contactor; an operating contactor 1 feedback used for detecting the state of the operating contactor 1 is connected to the PLC controller. Through adopting a variable frequency drive as the basic driving method, the driving control system is efficient and energy saving, and can be automatically switched to the Y-shaped - triangular drive when the frequency changer is in failure or damaged state, therefore, the normal operation of the escalator or the moving sidewalk is not affected, and the utility model has the advantages of simple structure and convenient control.

Energy recovery device in a variable-frequency drive

Abstract: A variable-frequency drive that includes a DC power supply bus with a positive line and a negative line, and an inverter module powered by the DC bus for supplying a variable voltage to an electric load. The inverter includes a first DC/DC converter including output terminals connected in series on the positive line of the DC bus, a second DC/DC converter including input terminals connected between the positive line and the negative line of the DC bus, a filtering capacitor connected in parallel to the input terminals of the first converter and to the first output terminals of the second converter, and an electric power storage module connected in parallel to the second output terminals of the second converter.

System and method for forming universal control panel

Abstract: A universal control panel for controlling operation of a cooling component. The universal control panel may have a variable frequency drive (VFD) that incorporates an input voltage and frequency sensing circuit; and logic, memory and communications circuits. The VFD accepts a plurality of differing input signals, analyzes the input signals and generates an output signal having a desired voltage and frequency to provide real time control over an electrical component operably associated with the cooling component. The VFD controls the cooling component in relation to changes in at least one of sensed pressure and a sensed temperature of a fluid, to dampen response of the electrical component, to thus achieve more efficient use of the cooling component being used to cool the fluid.

Method for Braking an AC Motor

Abstract: A system for braking a motor. The system includes at least one resistor and a contactor connected to the at least one resistor and a motor. The system further includes a variable frequency drive electrically connected to the motor, wherein the variable frequency drive comprises a controller operably connected to the contactor, wherein at least a portion of the contactor closes connecting the at least one resistor to the motor in response to a command from the controller. The variable frequency drive is configured such that motor flux levels may be maintained at a relatively high level as motor torque current is reduced, resulting in a consistently high motor flux level as the motor speed decreases.

Method and system for braking an ac motor

Abstract: A system for braking a motor. The system includes at least one resistor and a contactor connected to the at least one resistor and a motor. The system further includes a variable frequency drive electrically connected to the motor, wherein the variable frequency drive comprises a controller operably connected to the contactor, wherein at least a portion of the contactor closes connecting the at least one resistor to the motor in response to a command from the controller. The variable frequency drive is configured such that motor flux levels may be maintained at a relatively high level as motor torque current is reduced, resulting in a consistently high motor flux level as the motor speed decreases.

Electromechanical system having a variable frequency drive power supply for 3-phase and 1-phase motors

Abstract: An electromechanical system is configured with a variable frequency drive power supply which provides power to both a three-phase motor and to a single-phase motor. In some embodiments, the variable frequency drive also powers one or more additional motors.

Integrated fan drive system for air-cooled heat exchanger

Abstract: Is air-cooled heat exchanger integrated fan drive system. Integrated fan drive system, high-torque having a rotatable shaft, a low speed permanent magnet motor, a fan coupled directly to the rotatable shaft, and the permanent magnet motor to control the rotational speed of the permanent magnet motor and a variable frequency drive for communicating electrical signals. High torque, the permanent magnet motor is provided with two or more bearings which cooperates with the shaft. Variable frequency drive includes a variable frequency controller having an output for supplying an electrical signal to a control input and a high torque for receiving the AC power, the operating speed of the permanent magnet motor. Variable frequency drive is also user is provided with a user interface that communicates with variable frequency control returning electronic data signals to be input to the speed control data. Other embodiments of the present invention are described herein.

Harmonic Analysis of a Static VAR Compensated Mixed Load System

Abstract: As power electronic based controllers and loads become more prevalent in power systems, there is a growing concern about how the harmonics generated by these controllers and loads affect the power quality of the system. One widely used power electronic based load is the Variable Frequency Drive (VFDs) used to vary the speed of an induction motor; whereas a common example of a power electronic based controller used in power systems is the Static VAR Compensator (SVC) for improving a system's power factor. In this thesis, the harmonic content and overall performance of a system including both a VFD and a SVC will be studied and analyzed. Specifically, the cases of no compensation, static capacitor compensation, and power electronic based static VAR compensation are examined. A small-scale model of a system for study was constructed in lab. Several cases were then performed and tested to simulate a system which contained both fixed and power electronic based harmonic generating loads. The performance of each case was v determined by total harmonic current and voltage distortions, true power factor, and RMS current levels at different points in the system. vi ACKNOWLEDGEMENTS

Power system resonance excited by VFD ground fault

Abstract: This paper investigates the resonance phenomenon produced by a voltage source PWM variable frequency drive (VFD) on an ungrounded delta system. Many drives are installed on ungrounded delta systems without isolation transformers or other means to provide inverter ground reference. A drive output ground fault will not be detected by either the VFD or conventional power system ground fault protective relaying. Without a ground reference, the drive continues to operate with the motor phase grounded. This condition modulates the power system neutral and excites a system resonance when the system loading and damping are optimal. Since this ground condition can go undetected for long periods of time, there is a high probability the system will experience optimal resonance conditions. This condition excites a triplen harmonic above the 30th and produces amplitudes of 2.6 times voltage. The resonance bursts were recorded for as long as 200 milliseconds and a secondary resonance was recorded for longer periods. The secondary resonance is almost as destructive but lower in amplitude. These resonances will fail many types of electrical equipment. The problem may go undetected or unresolved for a long time. This paper presents the excitation mechanism, resulting resonance and ways to avoid the problem.

Torsional mode damping apparatus

Abstract: PURPOSE: A torsional mode damping system and a compression train are provided to reduce or relieve a harmful effect of alternative torsional pressure. CONSTITUTION: A torsional mode damping system comprises a torque sensor(12), a torsional damper(20), and a Variable Frequency Drive controller. The torque sensor generates a torque signal(14) based on a measured value of the torque of a gear shaft. The torsional damper is connected to the torque sensor and generates a torque correcting signal based on the torque signal from the torque sensor. The VFD controller is connected to the torsional damper and generates a VFD signal changed by the torque correcting signal.

Dynamic Performance Estimation of DFIG wind turbine under Balance /Unbalance grid fault condition

Abstract: The global electrical energy consumption is rising and there is a steady increase in the demand of power generation So, in addition to conventional power generation units a large no of renewable energy units are being integrated into the power system A wind electrical generation system is the most cost competitive, environmentally clean and safe out of all the renewable energy sources The recent evolution of power semiconductors and variable frequency drive technology has aided the acceptance of variable speed generation systems Slip ring induction motor in the variable speed double fed induction generator mode is largely used in wind turbine generation technology Therefore, a detailed model of induction generator is presented in the thesis Then the induction generator is operated at different operating conditions and the results are presented in the thesis A hardware set up is build up to estimate the different circuit parameter under different operating conditions Speed, torque, Active and reactive power estimation are proposed in the thesis with the help of hardware set-up Because these are the controllable parameter and they determine the machine performance So, by estimating these parameter our future aim is to manipulate those parameter and to design a closed loop controller for DFIG This study is relevant as DFIG-wind turbines are an integrated part of Distributed generation system Any abnormalities associated with grid are going to affect the system performance considerably Taking this into account, the performance of double fed induction generator (DFIG) variable speed wind turbine under network fault or under dynamic loading is studied The significant result of the analysis is also shown and being compared with the existing literature to validate the approach

Variable frequency drive with possible regeneration

Abstract: FIELD: electricity. ^ SUBSTANCE: brake diagram used in variable frequency drive includes set of one-phase power elements electrically connected for receiving power from supply and power fed to load. One-phase power elements contain the first row of regenerative power elements and the second row of non-regenerative power elements. Each non-regenerative power element is made in the form of inverter bridge, capacitor battery electrically connected between terminals of inverter bridge, and three-phase bridge rectifier electrically connected between terminals. Non-regenerative power elements can provide reactive power when set of elements is used for engine braking. ^ EFFECT: decreasing losses when power is returned to network. ^ 19 cl, 15 dwg

Energy recovery devices in the variable frequency drive

Abstract: A variable-frequency drive that includes a DC power supply bus with a positive line and a negative line, and an inverter module powered by the DC bus for supplying a variable voltage to an electric load. The inverter includes a first DC/DC converter including output terminals connected in series on the positive line of the DC bus, a second DC/DC converter including input terminals connected between the positive line and the negative line of the DC bus, a filtering capacitor connected in parallel to the input terminals of the first converter and to the first output terminals of the second converter, and an electric power storage module connected in parallel to the second output terminals of the second converter.