Showing papers on "Variable-frequency drive published in 2012"

Partial resonant AC link converter: A highly reliable variable frequency drive

Abstract: In this paper a soft switched ac link ac-ac converter is employed as a variable frequency drive (VFD). The proposed configuration is a reliable, efficient, and compact converter with unity power factor at the input side. It is, in fact, a partial resonant converter i.e. only a small time interval is allocated to resonance in each cycle. Hence, while the resonance facilitates zero voltage turn on of the switches and soft turn-off, the LC link has low reactive ratings and low power dissipation. Due to the soft switching of the switches, the switching frequency can be increased and the high frequency of the link minimizes the size of the passive components. Both buck and boost operations in forward and reverse directions are feasible through this converter. Moreover, this converter is capable of increasing and decreasing the frequency over a wide range. Other than regulating the output current pulses to control the speed of motor the control algorithm also controls the input power factor and therefore no external power factor correction circuitry is required. In this paper field-oriented control scheme is applied to the proposed VFD for controlling the speed of the motor. Both simulation and experimental results are included in this paper to verify the performance of the proposed VFD

Operational optimisation of water supply networks using a fuzzy system

Abstract: This paper presents a fuzzy system to control the pressure in a water distribution network, by using valves and controlling the rotor speed of the pumping systems. The variable frequency drive tracks the minimum head of the pumping system, while the control valves have the function of eliminating the excess pressure at various points of the network. The control system can track any reference pressure value and there is no limit for the number of monitored points. Experiments were carried out to demonstrate the fuzzy system’s efficiency. By extrapolating the results achieved in the experimental setup to a real hydraulic network with leakages and no pressure control, the volumetric losses could be reduced by more than 56%. The experiments showed that the system is robust enough to control the pressure of an experimental setup of water distribution. Besides, the proposed system can be easily applied to similar water supply systems and would help to reduce the consumption of water and electricity, as well as to reduce the maintenance costs.

VFD machinery vibration fatigue life and multi-level inverter effect

Abstract: The paper documents fatigue related mechanical failures in variable frequency drive (VFD) motor machinery due to mechanical vibrations excited by drive torque harmonics which are created by PWM switching. Present effort models the coupled system with full electrical system including rectifier, DC bus, inverter, motor, and an industrial mechanical system including flexible couplings, gearboxes and multiple inertias. The models are formed by a novel combining of a commercial motor code with a general, self-written mechanical code. The approach extends failure prediction beyond simple occurrence of resonance, to fatigue life evaluation based on Rain-flow algorithm, which is suitable for both steady state and transient startup mechanical response. The second contribution is a demonstration that the common use of multilevel inverter to reduce voltage/current harmonics may actually exacerbate resonance and fatigue failure. This is shown to be caused by a resulting amplitude increase of torque components in proximity to potential resonance frequencies.

Sewage Pumping System and Method

Abstract: A system includes a pump that is operative to move liquid out of a reservoir. The system also includes a depth level sensor that is operative to determine a depth level of the liquid in the reservoir, and a controller operatively connected to the depth level sensor. The system further includes a variable frequency drive operatively connected to the motor and the controller. Responsive to the determined depth level of the liquid increasing to a first level, the controller is operative to start operation of the motor. The variable frequency drive is operative to control the speed of the motor. The controller is operative to cause the variable frequency drive to output an optimum frequency that causes the motor to operate at substantially the lowest usage of energy to lower the depth level of the liquid in the reservoir from the first level to a second level.

Influence of the sinusoidal supply frequency on the induction motor stray load losses

Abstract: This papers deals with the influence of the supply frequency on the induction motor stray load losses. Due to the complexity of the stray load losses computation, a fully experimental approach has been chosen. Following the International Standard IEEE 112 method B, the additional losses have been determined in the supply frequency range of 30 Hz up to 80 Hz. As requested by this standard, a sinusoidal supply has been adopted for an 11 kW, 50 Hz, 400 V induction motor. In order to understand if the motor stator phase connection influences the stray load losses, the tests have been performed with both star and delta connections. The test results didn't show any influence of the motor connection on the stray load losses. About the supply frequency, the obtained results have shown a direct dependence of the stray load losses with the supply frequency. As a consequence, waiting the new International Standards which will define the rules for the induction motor efficiency determination with inverter supply, the results reported in this paper warn that the stray load losses are directly depending on the supply frequency and this cannot be neglected when the motor is used in variable frequency drive, in particular during the flux weakening operation.

Energy-saving automatic control device of cloth-bag dust removal system and control method for blast furnace dust removal

Abstract: The invention provides an energy-saving automatic control device of a cloth-bag dust removal system and a control method for blast furnace dust removal The energy-saving automatic control device comprises an input unit, a variable frequency drive unit, an execution unit and a PLC (programmable logic controller) control unit, wherein the input unit is composed of a fast acting fuse, a contactor and an electric reactor; the variable frequency drive unit consists of a rectification module and a capacitor, together with a braking unit, an inverter, a CPU (central processing unit) with a vector control function and a 220V power supply; the execution unit is composed of an electric reactor, a throttle rotary actuator and a throttle control device; the PLC control unit is composed of a PLC and an auxiliary circuit; the primary side of the rectification module of the variable frequency drive unit is connected with an output end of the electric reactor of the input unit and the secondary side of the rectification module is connected with the electric reactor of the execution unit through the capacitor and the inverter; the rectification module and the inverter are connected with the CPU through a bus, the CPU and the PLC are connected in a communication manner through a switching value and an analog quantity, and a throttle control end of the PLC unit is connected with the execution unit Meanwhile, the device is used for controlling the blast furnace dust removal By adopting the energy-saving automatic control device and the control method provided by the invention, the fan utilization can be improved, the accuracy control on the dust removal can be realized, the electric energy can be saved, heat productivity of the device can be reduced, the dust recovery rate can be improved, the cloth-bag damage rate can be reduced, and exhaust gas and dust emissions can be decreased

A comparative analysis of voltage magnitude deviation and unbalance on standard and premium efficient induction motors

Abstract: Experimental tests were carried out to determine if there are any noticeable differences in the way premium and standard efficiency motors operate under abnormal voltage conditions such as over voltage under voltage and voltage unbalance. The results for four motors are compared in terms of efficiency and overcurrent conditions and the differences in the performance of the motors are highlighted. In addition, two 3-phase motors were connected to a single phase variable frequency drive and the effect of voltage magnitude deviations on system efficiency was investigated.

An experimental evaluation of the effect of voltage distortion on the performance of induction motors

Abstract: A variable frequency drive operated motor was used to inject harmonics onto a bus bar on which a smaller line connected test motor is operating. The effect of voltage distortion on the operation of each test motor is investigated by measuring their operating efficiency. The motors tested comprise integral horsepower three phase motors of EPACT and NEMA Premium design as well as single phase motors. It was verified that distortion levels of about 8%THD have negligible effect on the operation of both the integral and single phase motors.

dsPIC based SPWM controlled Three Phase Inverter Fed Induction Motor Drive

Abstract: The induction motor fulfills admirably the requirements of substantially constant speed drive. This paper presents simulation and development of variable frequency drive by keeping constant voltage-frequency ratio of power supply which is fed to induction motor. A rule-based fuzzy logic controller applied to a scalar closed loop V/f induction motor (IM) speed control,in MATLAB environment. A fuzzy control system uses speed error and speed error variation to change both amplitude and frequency of supplied voltage. Reference speed and load torque variations are also simulated and implemented on hardware.

Triple cylinder with auxiliary gas over oil accumulator

Abstract: A hydraulic lift system for artificial lift pumping or industrial hoisting comprises a three chamber cylinder, a gas over oil accumulator, a large structural gas accumulator and a large flow pilot operated check valve. A matrix variable frequency drive, a standard variable frequency drive, an electrical squirrel cage motor or a natural gas engines are part of the main prime mover alternatives.

Regenerative variable frequency drive

Abstract: A regenerative variable frequency drive includes an active converter connected to an inverter. The converter has a filter capacitor, an inductor, two half bridges, bus bars that connect to the inverter and bus capacitors. The converter converts single phase AC power to DC power and DC power to single phase AC power, boosts the AC power, reduces input line harmonics, maintains input current in phase with utility voltage in order to achieve near unity power factor, and maintains constant DC voltage between the bus bars.

Measurement of a variable frequency drive loss and efficiency using both calorimeter and powermeter

Abstract: Variable frequency drive efficiency plays an important role in green energy applications. However, how to accurately measure drive loss and efficiency is still a question to the industry. This paper reviews the powermeter method, calorimeter method, and factors that affect accuracy. After a calorimeter is constructed and calibrated, a variable frequency drive is tested using both methods. Test results are compared and uncertainty analysis is given.

Extra long distance belt conveyor variable frequency drive control system

Abstract: The utility model relates to an extra long distance belt conveyor variable frequency drive control system which comprises a handpiece frequency converter, a machine tail frequency converter and an industrial computer control system. A programmable logic controller (PLC) in connection with the machine tail frequency converter in control mode is further provided. The PLC is communicated with an industrial computer through a wireless control network, and is communicated with the machine tail frequency converter at the same time, and therefore power balance adjustments of the handpiece frequency converter and the machine tail frequency converter can be achieved. The handpiece frequency converter is communicated with the industrial computer through an RS485 network. By means of the balance adjustment of the extra long distance belt conveyor variable frequency drive control system, a real automatic real-time adjustment can be achieved, and effect of the adjustment is good.

Maximum Efficiency Control - A New Strategy To Control Electrohydraulic Systems

Abstract: One of the most wanted goals on all fields of research is improvement of machines’ energy efficiency and electrohydraulic systems are no exception. Improvements of the control concepts can result in quite substantial energy savings. Equipping an electrohydraulic machine with a variable frequency drive controller and a variable displacement pumpgives an additional degree of freedom, whichenables maximum efficiency tracking for all operating points. Controlling such combination with a new control strategy called maximum efficiency control ensures that the pump always operates optimally. The presented maximum efficiency controller calculates the optimal pump setting (displacement, rotational speed) for each operating point (pressure, flow). Therefore, the electrohydraulic system is able to convert electrical energy to hydraulic energy with minimum losses. The following article presents the basic concept of the maximum efficiency controller. Furthermore it uses experiment to compare the maximum efficiency controller with other existing electrohydraulic drive concepts, such as a variable pump coupled with motor running at constant rotational speed and a fixed displacement pump driven by a speed controlled electromotor.

High-voltage power electronic combined switch

Abstract: The invention relates to a control technology for a power system, and aims to provide a high-voltage power electronic combined switch, which comprises a clamping capacitor and a plurality of reverse-conducting switches. The combined switch is formed by cascading a plurality of units. The combined switch can tolerate switching voltage which is far higher than that of a single power semiconductor device, is applied to high-voltage direct current transmission converters of power systems, power electronic transformers, a plurality of key high-voltage conversion and switching devices of smart power grids, high-voltage variable frequency drive devices, the direct grid-connected power generation of new energy sources, and high-voltage rectification and inversion devices in industrial application, has a simple modular structure, and is simple and reliable in control, suitable for working at high frequency, high in electromagnetic compatibility, easy to manufacture into a high-voltage switch module, free of remarkable voltage and power level bottlenecks and wide in technical application range. Certain sorts of combined switches also have the characteristics of bilateral switching and the like. Compared with those of like products, the volume, weight and cost of a conversion system consisting of the high-voltage power electronic combined switch are expected to be decreased remarkably.

Small online impact detection test stand

Abstract: The present invention is a small online impact detection test stand which is characterized in that: an accelerated mechanism is an inertial accelerator that a motor and a belt pulley drive a roller assembly to rotate through a pneumatic clutch mechanism and a wire rope pulls a sliding platform to move, a clutch for an automobile is used to drive the acceleration mechanism, a dynamic condition of automotive driving is effective simulated, a frequency converter is used to adjust an impact acceleration, and impact pulse width adjustment is formed through synchronous adjustment of variable frequency drive frequency and a waveform pad. Thus an impact acceleration value and a pulse width are continuously adjustable in a large range, and the needs of small laboratory detection and production on-line detection are satisfied.

Variable Frequency Drive Importance in an LPG Plant: Case Study

Abstract: The success of any plant is generally fostered by many factors that affect directly the production. The relevant ones are, low capital investment, low operating cost, and high production efficiency. Energy consumption is a key element that influences the operating cost factor. Indeed, the electrical power consumed by electrical motors in an LPG plant constitutes one of the major sources of energy consumption. Motorized systems’ optimization can generate important energy saving, improving and energy efficiency for the following systems: compressed air system, ventilation system and pumping system. Variable frequency drive offers many advantages in centrifugal pumps’ operation. It can improve process control, equipment reliability and cost savings. In this paper, a study of energy saving opportunity in pumping systems using low affinity equations is presented. For this purpose, three factors have been measured: the flow rate, pressure and the electrical power drawn by the electric motor. Energy efficiency of the existing system consisting of the pump driven by the electrical motor has been calculated using on site measured data.

Experimental investigation on variable speed operation of air conditioning

Abstract: Air conditioning installations are typically design ed with enough cooling capacity to satisfy the desired mini mum temperature under the heaviest load. Since heat loa ds tend to be less than the maximum designed loads, the system will most often be working under part-load rather than full-l oad conditions. Operating at these part-load conditions at fixed capacity will be more expensive than if the capacit y were able to match the required load. Varying capacity air co nditioning systems, which make use of inverter technology, have been developed in order to track the required cooling lo ad more closely. These high quality air conditioners are ad vertised as consuming around 30 per cent less energy than conventional systems. This experimental investigation looked into the ste ady state performance and start-up power requirements of an i nverter driven refrigeration unit versus fixed speed operat ion. A three phase (745 W motor) air conditioning laboratory set up was used in direct-on-line (fixed speed) mode and also with a variable frequency drive (inverter). The results obtained showed that the cooling coefficient of performance increased as the operating frequency was reduced. This means that an improved performance can be achieved at lower operating frequencies. A reduced start-up power was required for the inverter driven system, however the additional powe r requirements for the inverter resulted in the mains driven system being more efficient at full-load conditions . The improved coefficient of performance at lower freque ncies resulted in an improved performance for the inverte r driven system when compared to a conventional system at part-load conditions.

Modeling and Simulation of Permanent Magnet Synchronous Motor for Pure Electric Vehicle Based on Space Vector Pulse Width Modulation

Abstract: Space Vector Pulse Width Modulation (SVPWM) technique is one of the best method of PWM variable frequency drive and make the AC motor achieving the performance as good as DC motor. Permanent Magnet Synchronous Motor (PMSM) has many advantages of small volume, steady operation, high energy efficiency, large output torque, etc. To solve the problems of auto environment and energy sources, study on Pure Electric Vehicles (PEV) driven by PMSM based on SVPWM is an important research direction and has the practical value. On the basis of analyzing the basic models of SVPWM, PMSM and PEV, simulation model of PMSM Control System for PEV can be constructed. The results of the simulation show that the control system has super performance and meet the request of system.

Implementation Of Space Vector Pulse Width Modulation (SVPWM) For Three Phase Voltage Source Inverter Using Matlab Simulink

Abstract: Space Vector Modulation (SVM) was originally developed as vector approach to Pulse Width Modulation (PWM) for three phase inverters. It is a more sophisticated technique for generating sine wave that provides a higher voltage to the motor with lower total harmonics distortion. Space Vector Pulse Width Modulation (SVPWM) is an advanced method which is a computation intensive PWM method and possibly the best technique to variable frequency drive application. This project focused on the development of MATLAB/SIMULINK model of SVPWM step by step. Firstly, model of a three phase Voltage Source Inverter (VSI) had investigated based on space vector concept which is developed by equation then create model based on these equation. The next step is simulation the model of SVPWM and SPWM using MATLAB/SIMULINK. The outcome of simulation results demonstrated. Finally, this paper also covered the comparison of the total harmonics distortion between SPWM and SPWM.

Variable Frequency Drive Applications and Their Electrical Protection Scheme for Liquids Pipelines

Abstract: Motor and pump units can start either directly across the line (utility) or through a VFD. If the power system is weak (high impedance and relatively low available MVA), the result will be limitations on the maximum size of motor that may be started directly across the line. Currently some available power systems are not capable of starting large motors across the line and therefore VFD systems are required.A VFD can be used for starting purposes or to operate a motor/pump unit (unit) continuously. Liquids pipelines have been using VFDs for unit starting purposes and for pressure control while either one of the units connected to the VFD or while there is a dedicated VFD per unit.One VFD can be used to operate all the units. The VFD starts the motor, ramps it up, and synchronizes it with the utility to switch the motor from VFD operation to utility operation. The VFD follows the same sequence with the next unit. The VFD also switches the motor from utility operation to VFD operation. With pumps in series, one unit can remain connected to the VFD for pressure control in liquids pipelines.Each unit can also be controlled by a dedicated VFD, allowing independent control of each unit for start-up and speed control. Both single VFD or dedicated VFD per unit offer advantages. Benefits of using a single VFD for all units are cost savings for some applications, a backup start across the line when allowed by the power system, and station pressure control. The benefits of a dedicated VFD per unit application include more flexibility in flow and pressure control, ease of expansion without interrupting existing operations for an extended period, energy efficiency, and redundancy.Motor protection schemes for the above two VFD applications are discussed and compared in this paper. In order to maintain a safe and reliable pipeline system, comprehensive motor protection functions are provided to the pump unit. Although the principles are the same, there are some differences between the two motor protection applications.For a dedicated VFD per unit application, the VFD protection/control circuitry normally provides motor protection because the motor is always connected to the VFD. RTDs over-temperature protection is not typically a standard feature of VFDs, however, it can be provided by proper PLC programming or the VFD incoming feeder protection relay.Copyright © 2012 by ASME

Method for the control of luminance of gas discharge lamps

Abstract: A system for the control of luminance of a gas-discharge lamp, which includes a variable frequency drive (VFD) accepting AC voltage supply. The VFD is has a constant ratio of frequency to AC voltage ratio of the output. Raising the frequency of the output of the VSD would result in an equivalent rise in the voltage. Typically, a ballast on the input AC of the lamp is required and the power factor correction capacitor usually associated with the lamp is to be removed.

Energy efficient sewage pumping system with a controller and variable frequency drive and method

Abstract: A system includes a pump that is operative to move liquid out of a reservoir. The system also includes a depth level sensor that is operative to determine a depth level of the liquid in the reservoir, and a controller operatively connected to the depth level sensor. The system further includes a variable frequency drive operatively connected to the motor and the controller. Responsive to the determined depth level of the liquid increasing to a first level, the controller is operative to start operation of the motor. The variable frequency drive is operative to control the speed of the motor. The controller is operative to cause the variable frequency drive to output an optimum frequency that causes the motor to operate at substantially the lowest usage of energy to lower the depth level of the liquid in the reservoir from the first level to a second level.

VIBRATION ANALYSIS OF PUMP WI TH VFD TECHNOLOGY (Industrial Application)

Abstract: A Variable Frequency Drive (VFD) regulates the speed of a 3-phase AC electric motor by controlling the frequency and voltage of the power it delivers to the motor. Today, these devices (also known as Adjustable Speed Drives or Variable Speed Drives) are becoming prevalent in a wide range of applications throughout industry, from motion control applications to Cooling Towers, from water treatment facilities to machining areas, and many others. Considering the Economical and Environmental factors, it is advisable to modify the existing system rather than replacing it with new one. This project exercises this concept of vibration control in order to obtain smooth running by soft water pump and cooling tower pump.

Motion control - Fault diagnosis in Machines using VHDL

Abstract: The machines which have become a part of present day life, even in some cases it overcome human working ways. So for there is majo r concern in functioning of motor drives because a minute faulty function of motor may lead to drastic damage in working environment. Thus before entering into the fault diagnosis of induction motor the speed control is an important aspect. The speed control in induction motor can be done using SVPWM technique. From the past several years, much progress has been made in Art ificial Intelligence (AI) technology. Simp lified models of neural processing in the brain have been viewed as artificial intelligence in neural networks. It's an inexpensive, reliab le and non- invasive Artificia l Neural Network (ANN) based fault diagnosis. Multilayer Perceptron (M LP) is to be used in this paper because the input data contain continuous feature. The fault diagnosis in induction motor using AI technology can be done without resuming the function of induction motor an advantage of this approach compared with other techniques for fault diagnosis(1). This paper presents the new technique relevant to the design method of artificial intelligence based on VHDL hardware description language and FPGA imp lementation. The simu lation results are obtained from XILINX 12.2 software. I. Introduction In the past few years most of the methods are based on knowledge of status equation for fully or partially controlled systems. However status equation can't be easily obtained. Therefore we go for a smart control method with self-learn ing capability for better control performance. Thus here in this paper induction motor fault diagnosis and its motion control are going to be delt. Our design users Neural Netwo rk for its amazing effect which tradit ional controllers cannot achieve, when the system involved in an uncertain, time vary ing or non- linear status. The speed control of induction motor is the main process to be undergone before fault diagnosis is performed. The speed of the motor is of major concern in detection of fault. The speed control and fault diagnosis are performed in comparat ive manner (1). The speed control of induction motor is performed by space vector pulse width modulation (SVPWM). Thus three level voltage fed PWM inverter, which shows popularity in industrial drive applicat ion. The output voltage waveform which is generated by mult ilevel inverter. It can be generated at low switching frequency with high efficiency and low distortion. This is the reason why large voltage between the series device is easily shared. The space vector PWM technique is very popular which results in higher magnitude of fundamental output voltage available. The SVPWM is an advanced computation- intensive PWM method and it's the best among all other PWM method as it functions at variable frequency drive applications (2). II Speed Control of motor A voltage source inverter type Space vector pulse width modulation for controlling the speed of the induction motor is performed. The pulse width modulation in which several pulse are produced in each half cycle but width of each pulse is not same as in case of mult iple pulse width modulation however the width of each puls e is varied in accordance with the amplitude of the sine wave reference voltage. The Space Vector Modulation (SVM) is normally implemented using the direct method. The space Vector is an algorith m for the control of PWM. The principle behind SVPWM is that voltage vector which is to be approximated by using three adjacent vectors. To drive a 3phase AC powered motor at varying speed we require alternate current waveform wh ich can be generated using SVM. Thus Fig 1 shows the SVPWM wave model in response to the sinusoidal input wave. The SVPWM is generated mainly based upon the positive and negative cycles of the sinusoidal wave. The space vector diagram which consist 8 vectors these vectors are given as input to the IGBT inverter through which the speed of the induction motor is controlled. Taking into consideration of these 8 vectors among which 6 vectors starting from V001 to V110 is for supplying signal to Switch ON the transistors present in the IGBT inverter.

Variable frequency drive voltage boost to improve utilization

Abstract: A variable frequency drive system including an alternating current electrical power source, an alternating current motor and a variable frequency drive connected to the power source and the motor. The variable frequency drive provides electrical power to the motor, and includes an active rectifier to convert a first alternating current from the power source to a direct current and an inverter to convert the direct current to a second alternating current. A variable frequency drive output voltage is greater than a variable frequency drive input voltage, compensating for the motor apparent current. A method of electrical power conversion includes urging a first alternating current from a power source to a variable frequency drive. The first alternating current is converted to direct current via an active rectifier of the variable frequency drive, and the direct current is converted to a second alternating current via an inverter of the variable frequency drive.

Comparison of different variable speed compression train configurations with respect to rotordynamic stability and torsional integrity

Abstract: Wherever a variable speed gas compression train is needed for Oil & Gas upstream applications as well as for gas storage applications the primary decision has to be made between a gas turbine driver and an electric motor controlled by a variable frequency drive (VFD). A second decision has to be made between a high speed direct driven train and a low speed driver (gas turbine or motor) driving the compressor via a speed increasing gear. Finally it has to be decided whether a classical, oil lubricated train arrangement shall be used or if a high speed, oil-free, magnetic bearing levitated train configuration shall be chosen. With these three major decisions a variety of different train configurations are possible. They differ from each other in many technical aspects and therefore have strengths and weaknesses which can be rated in order to facilitate the evaluation of the optimum equipment configuration for a certain application. This paper specifically concentrates on the comparison of rotordynamic key figures like the logarithmic decrement (damping) of the lowest bending mode, the presence of overhung coupling modes within the speed range or the presence of torsional critical speeds which can be excited within the speed range and which therefore might adversely affect the integrity of the train components. The evaluated configurations include modern hermetically sealed, oil-free, magnetic bearing levitated compressor designs. Based on these key figures this paper will benchmark the rotordynamic

Amplifier for frequency variator. (Machine-translation by Google Translate, not legally binding)

Abstract: Variable frequency drive, or the acronym afd. The present invention proposes a frequency converter for electric motor. This variator is characterized by the fact that it comprises an artificial neuron for each phase of the motor, where one of its inputs is a first synthesis signal generated by a digital control and processing unit with analog outputs, and its output is connected to the motor . (Machine-translation by Google Translate, not legally binding)