Showing papers on "Variable-frequency drive published in 2008"

Controlled centrifuge systems

Abstract: The present disclosure is generally directed to centrifuge systems and methods for controlling centrifuge systems, wherein the systems in certain aspects are adapted for processing material, e.g., but not limited to drilling fluids with solids therein. One illustrative method includes providing a centrifuge system that is made up of, among other things, a bowl, a bowl motor system, a bowl variable frequency drive, a conveyor, a conveyor motor, a conveyor variable frequency drive, a pump, a pump motor, and a pump variable frequency drive. Additionally, the centrifuge system includes a control system that is adapted to control the bowl variable frequency drive, the conveyor variable frequency drive, and the pump variable frequency drive. The method includes controlling the centrifuge system in the G-force differential control mode by controlling the G-force on the bowl as the bowl is rotated by the bowl motor system so that the G-force on the bowl does not exceed a pre-set maximum G-force.

Linear Fresnel solar arrays and drives therefor

Abstract: Described herein are solar energy collector systems, components for solar energy collector systems, and methods for installing solar energy collector systems. The components for solar energy collector systems include but are not limited to solar radiation absorbers, receivers, drives, drive systems, reflectors, and various support structures. The solar energy collection systems, solar radiation absorbers, receivers, drives, drive systems, reflectors, support structures, and/or methods may be used, for example, in LFR solar arrays. Drives and drive systems are described herein that may provide improved rotational positioning, movement, and/or rotational positional sensing. For example, drives and drive systems are provided which allow operation through a variable frequency drive. The components and methods described herein may be used together in any combination in a solar collector system, or they may be used separately in different solar collector systems.

Linear fresnel solar arrays and components therefor

Abstract: Described herein are solar energy collector systems (201), components for solar energy collector systems (201), and methods for installing solar energy collector systems (201). The components for solar energy collector systems include but are not limited to solar radiation absorbers (205), receivers, drives, drive systems, reflectors (211a), and various support structures. The solar energy collection systems (201), solar radiation absorbers, receivers (205), drives, drive systems, reflectors, support structures, and/or methods may be used, for example, in LFR solar arrays. Improved solar radiation absorbers, receivers and related methods are described here. Drives and drive systems are described herein that may provide improved rotational positioning, movement, and/or rotational positional sensing. For example, drives and drive systems are provided which allow operation through a variable frequency drive. The components and methods described herein may be used together in any combination in a solar collector system (201), or they may be used separately in different solar collector systems (201).

Photovoltaic integrated variable frequency drive

Abstract: A photovoltaic (PV) integrated variable frequency drive system having a variable frequency drive and an energy source. The variable frequency drive having a back end inverter, a DC bus electrically connected to the back end inverter, and an active front end electrically connected to the DC bus to facilitate bi-directional power flow to and from a power grid. The energy source being electrically connected to the DC bus.

Retrofitting a constant volume air handling unit with a variable frequency drive

Abstract: A system and methods providing real-time monitoring, management and control of a variable frequency drive retrofit to a constant volume air handling unit without making significant mechanical or control system changes. Customers and vendors are provided with a more informative and economically attractive air handling unit. The system also provides a finer granularity of control over conditioned air properties such as temperature, humidity and air quality.

Analysis Guide For Variable Frequency Drive Operated Centrifugal Pumps

Abstract: The use of variable frequency drives (VFD) in pumping applications with variable-duty requirements provides the user with a variety of benefits, including potentially significant energy savings and improved reliability achieved by means of speed reduction and avoiding part-flow operation. Energy savings are primarily realized by running the equipment at high levels of efficiency and optimal operating speeds, matching the generated pump head to the exact system requirements without the use of energy consuming control valves. Running pumps at lower operating speeds and avoiding part-flow operation also positively influences component life and between maintenance intervals. The primary mechanical challenge of any VFD application is the wide continuous operating speed range. Excitation frequencies of fixed speed applications miss most natural frequencies of the structure, rotor, etc., and therefore potentially harmful resonance conditions often do not occur. This is no longer the case with VFD applications, where excitation frequencies become variable and the likelihood of encountering resonance conditions is greatly increased. Problems ANALYSIS GUIDE FOR VARIABLE FREQUENCY DRIVE OPERATED CENTRIFUGAL PUMPS

Half-bridge bidirectional DC-DC Converter for small Electric Vehicle

Abstract: This paper describes a bidirectional DC-DC converter for a small electric vehicle. The DC-DC converter designed and tested is capable of raising the voltage from the battery pack (96 V nominal) to 600 V necessary to feed the variable frequency drive that controls the induction motor. This converter is also capable of working in the opposite direction (600 V to 96 V) in order to capture energy from regenerative braking and downhill driving. Since our EV is designed to have multiple energy sources - batteries, supercapacitor and solar panels - this same converter will be used in parallel, one for each source, having thus a multiple power converter.

AC motor bypass with fault annunciation, serial communication and fault tolerant coil control

Abstract: A motor bypass is controlled by a digital signal processor (DSP) with embedded control software that allows fault detection and annunciation, serial communications between both a variable frequency drive (VFD) and a bypass controller and the bypass controller and a host computer. The use of the DSP and embedded control software further allows for contactor coil control to provide fault tolerant operation as well as fault condition detection and annunciation to the user.

Integrated Fan Drive System For Cooling Tower

Abstract: A drive system for driving a fan in a wet cooling tower, wherein the fan has a fan hub and fan blades attached to the fan hub. The drive system has a high-torque, low speed permanent magnet motor having a motor casing, a stator and a rotatable shaft, wherein the rotatable shaft is configured for connection to the fan hub. The drive system includes a variable frequency drive device to generate electrical signals that effect rotation of the rotatable shaft of the motor in order to rotate the fan.

Real time optimization of power in electrical submersible pump variable speed applications

Abstract: A method and apparatus for real-time monitoring of a variable frequency drive (VFD) controlling an electric submersible pump (ESP) and for fine-tuning operation of a VFD-ESP system such that oil production, power, and motor run life are optimized.

Variable frequency drive as a source of condition monitoring data

Abstract: Variable speed drives are gaining popularity as an efficient way to power industrial motors. They collect and compute a large number of signals, normally used for control and operation purposes (for example, current, torque, speed, frequency, power, flux, etc.). This data is available and can be used for diagnostic purposes. These signals can be analyzed for their spectral content, for monitoring the operating point, for examining cyclic processes, etc. On the down side, the format, quality and quantity of data is determined by the hardware. Further complication arises from the fact that variable speed drives change the output frequency to follow desired process parameters. Methods for circumventing these difficulties are presented along with actual results from various drive-powered processes. These results prove that a variable speed drive can be a valuable source of diagnostic data not only for the drive itself, but also for the entire driven process.

Dynamic braking load analyzer

Abstract: A dynamic braking load analyzer that determines the proper resistance value for a dynamic braking load resistor to be used in combination with a variable frequency drive or servo-drive to accommodate the power dissipated from an induction motor when it is being reduced in speed. The analyzer includes a resistor bank having a plurality of resistors electrically coupled in parallel. Switches are provided between the resistors, and a resistor selector switch determines which resistors are switched into the resistor bank circuit. A heat sensing resistor in the resistor bank measures the heat generated by the resistors and provides a signal that is read by a heat meter. The combination of the temperature measurement and the resistance of the resistors in the circuit gives the proper braking resistance value for the deceleration of the induction motor.

Load modeling of an induction motor operated with a variable frequency drive

Abstract: Knowledge of load characteristics and load modeling is a necessary tool for adequate voltage stability analysis. This paper presents experimental tests of an off-the-shelf variable frequency drive feeding an induction motor and shows how this load draws power from the grid and its effect on the voltage stability. A description and simulation of the drive is provided to understand the input and output waveforms observed. The results show that commonly used exponential load models of the induction motor, compared to the drive-fed motor, are completely different for reactive power, but very similar for real power. Calculation of power factor for the loads with high harmonic distortions, like the motor drives, and its application to the stability analysis are discussed. It is also shown that the motor-drive increases the maximum power transfer limit for voltage stability and reduces the voltage drop, compared to the induction motor alone.

Invester Fault Diagnose Based on Detecting DC Side Current

Abstract: For diagnosing the inverters transistor base drive open fault in variable frequency drive system, the frequency spectrum in normal, open fault of one transistor and open fault of two transistors in one phase is analyzed by introducing the double Fourier transfor of the switch function: The low frequency spectrum of DC side current contains DC component only when the inverter runs in normal; The low frequency spectrum of DC side current contains the DC component and some harmonic of modulation signal when one transistor is open; The low frequency spectrum of DC side current contains the DC component and the second harmonic of modulation signal only when two transistors in one phase are open. The open fault of one transistor and open fault of two transistors in one phase can be examined by detecting the frequency components of DC side current. Theoretical analysis is verified by esperinent results.

Energy efficient technologies for railway escalators

Abstract: This paper is to present the reviewing results on the design and implementation of energy efficient technologies and their future development and applications of the vertical transportation system -escalator in the railway industry. Two alternative methods [1] are introduced to reduce energy consumption of escalator in the railway industry. The first one called "VSD" method, by installation of a variable frequency drive to link up with the scheduling control scheme. The second is to design a special "VVC" controller to reduce the energy by controlling the motor voltage and improving motor power factor when only fewer people using the escalator but keeping the speed constant.

Smart blow-down system for variable frequency drive compressor units

Abstract: A method and apparatus for blowing down a compressed air system when temperature is at or below a predefined temperature threshold is provided. Temperature sensors in the compressed air system monitor temperature and a control processor determines when the temperature is at or below the predefined temperature threshold. When it is determined temperature is at or below the predefined temperature threshold, the control processor operates a solenoid blow-down valve that depressurizes the compressed air system.

Method for dynamic well operation with electric pump having variable-frequency drive

Abstract: FIELD: oil production from wells, particularly to operate wells provided with electric pumps, for instance with submersed pumps with ac electronic motors. ^ SUBSTANCE: method involves pumping-out liquid with electric pumps having ac electronic motor; periodically increasing ac electronic motor rotational frequency as motor operates in steady-by regime at time intervals defined by duration of transient processes in well-reservoir system, wherein rotational frequency is increased for value determined by threshold of motor current sensitivity, to reduce ac electronic motor current value below threshold one at a given rotational frequency corresponding to pump starvation; making a decision whether critical dynamic liquid level is achieved in well from pump starvation. Threshold value of ac electronic motor current is determined from test-bench characteristics with taking into decision of density of liquid to be actually pumped-out. After pump starvation detection the ac electronic motor is shifted into standby mode with decreased rotational frequency to prevent ac electronic motor overheating. Standby mode duration is enough to change dynamic liquid level in well. After standby mode termination ac electronic motor rotational frequency is again increased to value less than pump starvation one, wherein difference between said two values is equal to predetermined one. After that electric pump is brought into operation in mode near that providing critical dynamic liquid level in well to increase liquid influx in well. ^ EFFECT: increased efficiency of selection of working pump regime, which maximizes well rating due to elimination of pipe string pressure measurement. ^ 3 dwg

Unti-disturbance measures in the variable-frequency drive system of drilling rig

Abstract: The voltage and current waveforms of the variable-frequency drive system in site are statedThe main factors of the electromagnetic disturbance and various unti-disturbance measures are analyzedAnd an active dynamic filter is also depicted

A Study on the Performance Analysis for Power Converters of Electric Propulsion Ship

Abstract: Electric propulsion motors are operated from a variable frequency drive, which supplies power to motors at a frequency appropriate to the desired speed. The objective of this study was to evaluate power converters for shipboard applications and to recommend converters that meet lower harmonic distortion levels and torque ripples. Two systems were studied in detail : Cyclo-converters and PWM-converters. Cyclo-converters are the obvious choice where size, weight and efficiency are the most critical issues. However they have a disadvantage in power factor and they produce severe torque ripples in the motor which makes them unacceptable without special systems. PWM-converters produces better motor current waveform and eliminates common mode voltage issues at the motor, but suffers a multiple stages of power conversion and the isolating transformer. Results of this case study show that PWM-converters are more advanced and efficient drives for induction motor of electric propulsion ship.

Variable speed drives and centrifuges for zone 1 hazardous areas

Abstract: Using a variable frequency drive (VFD) provides a standard solution to get the top performance of machines in many applications in the process industry. Today, there is no solution to install frequency converters inside the hazardous area. This limits the functionality and the ability for a compact solution to a Zone 1 installation. Due to the heat generated from the power electronics, many control systems have to be installed outside the hazardous area or alternative systems like hydraulic or gear drive are used. The new concept of a VFD can be installed inside the hazardous area and close to the machine, thus providing the solution to build compact skid mounted systems for Zone 1. The most important criteria regarding the explosion protection is the heat dissipation of the power electronics. This new concept is shown in an application with a VFD with 22,5 kW power. The PLC as well as the power electronics is built in one control panel which is used to control a modern decanter centrifuge with a torque dependant scroll drive. Via this system the centrifuge adapts itself to varying operating conditions such as solid loads and feed rate, resulting in optimum cake dryness. The paper will address how to cover the occurring ignition sources by measures in a practical manner, and how to implement them with a centrifuge using the VFD control panel.

Integrated fan drive system for cooling tower and method of operating wet cooling tower

Abstract: An integrated fan drive system for a cooling tower comprising a high-torque, low speed permanent magnet motor having a rotatable shaft, a fan comprising a hub that is directly connected to the rotatable shaft and a plurality of fan blades that are attached to the hub, and a variable frequency drive device in electrical signal communication with the permanent magnet motor to control the rotational speed of the permanent magnet motor. The high-torque, permanent magnet motor comprises no more than two bearings in operative association with the shaft. The variable frequency drive device has a variable frequency controller that has an input for receiving AC power and an output for providing electrical signals that control the operational speed of high-torque, permanent magnet motor. The variable frequency drive device also includes a user interface in electronic data signal communication with the variable frequency controller to allow a user to input motor speed control data.

Method for dynamic well operation with the use of electric pump with variable-frequency drive

Abstract: FIELD: oil production, particularly to operate wells provided with electric pumps, particularly submersed electric pumps with valve actuators. ^ SUBSTANCE: method involves periodically repeating cycles; activating electric pump as supply voltage frequency increases and supplying liquid with electric pump at a given rotary speed. Liquid is pumped out with the use of electric pump with frequency-regulated drive and ac electronic motor. Regime characterized by constant current corresponding to initial dynamic liquid level in well is fixed. During electric pump operation ac electronic motor current behavior in time is continuously controlled. At each current elevation to value exceeding admissible value corresponding to current rotary speed ac electronic motor current rotary speed is increased for predetermined value defined from threshold ac electronic motor current sensitivity until said current variation is stopped or decreases to value less than admissible one corresponding to current rotation speed. At that if ac electronic motor current does not vary electric pump is shifted into stabilization mode at new dynamic level close to initial one. As ac electronic motor current decreases to value less than admissible one ac electronic motor rotation speed is reduced for predetermined value specified by ac electronic motor current sensitivity threshold. Then electric pump is shifted into cyclic mode when average dynamic level is close to initial one. ^ EFFECT: increased operational efficiency for well with varying productivity due to minimized dynamic level change. ^ 2 dwg