Showing papers on "Variable-frequency drive published in 2014"

Method of controlling a 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.

Design and implementation of dynamic electronic load controller for three-phase self-excited induction generator in remote small-hydro power generation

Abstract: This study presents design and implementation of a dynamic electronic load controller (DELC) for voltage and frequency control of a three-phase self-excited induction generator (SEIG) driven by constant power unregulated small-hydro turbine. This DELC is a combination of insulated-gate bipolar transistor-based voltage sourced converter (VSC) and variable frequency drive (VFD) which is connected across the DC link of VSC. The VFD operates in direct torque control mode and is coupled with a pumping system. The DELC is connected at point of common coupling in parallel with consumer loads. The VSC provides instantaneous control of the SEIG voltage through reactive power compensation. The VFD consumes the power in excess of consumer loads to maintain constant generator output power which in turn regulates the frequency. The excess generated power consumed by the VFD is used to pump water either to an overhead tank or for irrigation purposes. The performance of the proposed DELC of SEIG is demonstrated under various types of loads such as linear/non-linear, balanced/unbalanced loads and so on. Test results recorded on a developed DELC of SEIG exhibit simultaneous voltage and frequency control capabilities of the DELC under varying loads.

Static synchronous compensator-variable frequency drive for voltage and frequency control of small-hydro driven self-excited induction generators system

Abstract: In this study, a static synchronous compensator (STATCOM) along with a variable frequency drive (VFD), is proposed for voltage and frequency control of a small-hydro turbine driven self-excited induction generator (SEIG) system. STATCOM is used to control SEIG terminal voltage through variable reactive power injection. A control algorithm based on adaptive noise cancellation filter is proposed for STATCOM control. A field oriented controlled VFD feeding an induction motor is used to control system frequency. The VFD consumes active power in excess of consumer loads and thereby it regulates the system frequency. The excess power consumed by the VFD is utilised for pumping water to either an overhead storage tank or irrigation purposes. Besides the voltage control as primary objective, the STATCOM also provides harmonic currents compensation and load balancing under unbalanced non-linear loads. The proposed method of voltage and frequency control using STATCOM-VFD combination is implemented on a 3.7 kW SEIG and the test results are presented to demonstrate its performance.

Fixed frequency high-pressure high reliability pump drive

Abstract: An apparatus configured to hydraulically fracture an earth formation, includes a pump configured to hydraulically fracture the earth formation by pumping a fracturing liquid into a borehole penetrating the earth formation and an electric motor having a rotor coupled to the pump and a stator. A motor control center is configured to apply an alternating electrical voltage having a fixed-frequency to the stator in order to power the electric motor, wherein the apparatus and motor control center do not have a variable frequency drive.

Method and system for damping vibrations in a tool string system

Abstract: The invention provides a control system and method for limiting vibrations in a tool string system, comprising a relatively heavy rotatable device, such as a pump system or a bottom hole assembly, connected to an long rotatable tool string driven by a drive system. The 5 control system comprises feedback of both torque and rotational speed signals to correct the set rotational speed. An objective is to maintain the drive speed over torque ratio equal to the connected tool string impedance. A secondary objective, for lower frequencies, 10 is to approach and maintain a setpoint speed as drive rotation speed. The system may include a rotational speed sensor and a torque sensor, with the latter optionally replaced by a motor torque signal already available from a variable frequency drive (VFD) for an AC motor and the 15 current safeguarding signal for a DC motor.

System, apparatus, and method for controlling a motor

Abstract: Mechanisms are provided to control the operation of a motor. In particular, a variable frequency drive motor controller is described which resides within a motor housing. Additionally, the speed at which the motor operates is based on a signal received from a Hall Effect switch or from a communication device in communication with a remote interface. The Hall Effect switch is also described; in particular, the Hall Effect switch features a magnet rotatably connected with one side of a motor housing. A Hall Effect sensor, located on the opposite side of the motor housing, detects the position of the magnet and outputs a signal to the motor controller, located within the motor housing, indicating the detected magnet position. Additional operating features are described relating to the safe operation and control of the motor in potentially hazardous environments.

Energy Conservation Using Variable Frequency Drive in Pumping Application

Abstract: Pumping systems account for nearly 20% of the world's electrical energy demand and range from 25-50% of the energy usage in certain industrial plant operations(1).Pumping systems consume a significant portion of the electricity, Variable frequency drives (VFD's) are often recommended as a way to save pumping energy. Actual energy savings will vary greatly depending on how the discharge pressure of the constant speed pump is controlled and how it is operated after the VFD is installed. In the present work, the flow of pump has been controlled by two different methods, Matlab simulations and experimental work has been carried out and comparative statement is given in this paper. Index Terms - Centrifugal pump, flow control, throttling, variable frequency drive(VFD),Energy saving,Pulse Width Modulation(PWM).

Performance evaluation of current control strategies in LCL-filtered high-power converters with low pulse ratios

Abstract: In this paper, four current control strategies for voltage source PWM inverters with LCL-filter at extreme low pulse ratios (e.g. 80 Hz load frequency/600 Hz carrier frequency) are investigated. The system is a medium-voltage variable frequency drive (VFD) application with the power rating over 20 MW. The benefits and drawbacks of each scheme are summarized to provide a guideline for the current control loop design. The stability, dynamic response and the resonance damping effect of passive or active damping strategies are analyzed via a precise double-sided frequency modeling method. The system cost, algorithm complexity and dynamic performance are considered as well. Besides, analysis methodology based on the double-sided spectrum for such applications is demonstrated. Finally, the results have been validated in time-domain simulations.

Impacts of modern residential loads on power grids

Abstract: Modern residential loads use variable frequency drive motors and solid state electronics to improve operational efficiency and reduce energy consumption. The drawback of such energy efficient loads is the introduction of harmonics onto the local distribution grid. Elevated harmonic content due to the increased use of such devices can potentially impact residential distribution networks and adjacent customers. This paper quantifies the current harmonics generated by modern appliances, subsequently fed back to distribution grids. Multiple tests were performed using typical, commercially available appliances and results were analyzed against the IEEE-519-1992 power quality Standard. Research findings will be used to estimate harmonic content on the power grid, model future residential distribution networks and clarify the need to update the IEEE-519-1992 Standard.

Sensorless Start-up and Control of Permanent Magnet Synchronous Motor with Long Tieback

Abstract: The master thesis is a further investigation of the start-up procedure of a permanent magnet synchronous motor operated by variable frequency drive without position feedback via a long cable and transformers; as proposed in the specialization project, fall of 2013. The challenge is how to avoid large saturation in the transformers and motor while achieving the maximum possible starting torque with high cable resistance. In order to model and simulate the electrical system, the simulation software Simulink is used. A theoretical review is conducted in order to understand how to model system components, and how to start-up a permanent magnet synchronous motor while avoiding saturation in the transformer. Using the attained theoretical background, two permanent magnet synchronous motor Simulink models (with and without damper windings), an accurate pump load Simulink model, and three scalar control schemes which includes transmission system components for their control algorithms have been produced. In addition, a vector control scheme using field oriented control and extended Kalman filter for position estimation has been evaluated. A study case comprising of a permanent magnet synchronous motor operated by a variable frequency drive without position feedback via a long cable and transformers has been defined. The purpose of the study case is to study the defined control schemes, the permanent magnet synchronous motor's start-up procedure, and the electrical system's steady state behaviour. This include investigation of input parameter effects on the start-up procedure. The simulation results using the implemented pump load Simulink model shows that accurate load modelling affects the start-up procedure, as additional torque is required due to more rotational friction components. The simulation results of the study case show that the three proposed scalar control methods all are able to start-up the motor successfully, regardless of the initial rotor position. However, stability is not guaranteed at certain speed ranges due to the rise of small system disturbances. It has been shown that stability all through out the entire applied frequency range can be guaranteed by adding damping to the system. This is can be done by either adding transmission system components, motor damper windings, or a stabilization loop via frequency modulation.\pe It has been shown that cable length and applied frequency determines the accuracy of the transmission system voltage drop compensation algorithms of the proposed scalar control schemes. Increase in applied frequency and cable length increases the inaccuracy of the voltage drop compensation algorithms due to the ignored cable capacitance. Assuming that the maximum allowed voltage deviation from the required motor voltage during steady state is 0.1 pu, the longest cable length that can be used with the proposed scalar control schemes is 40 km. An exception is the open-loop scalar control scheme using constant voltage boosting, which can be used for cable lengths up to 20 km, due to its inaccurate calculation assumptions. Additionally, it has been shown that the breakaway torque and the reference frequency ramp slope used by the controllers directly affect the torque oscillations during start-up. Additional torque oscillations can be experienced if the breakaway torque is too high or if the reference frequency ramp slope is too low due to the lack of torque build up, which consequently makes the start-up time higher. The vector controller gave the best performance during load step tests due to its precise control of the rotor field. However, due to the requirement of rotor position feedback, position estimation is required. The investigated position estimation technique, extended Kalman filter is able to estimated speed and position with very little error. However, the initial rotor position is required by the extended Kalman filter algorithm in order to predict states properly. Simulation results show that the vector control scheme offers the lowest possible start time due to its high performance. However, due to the requirement of initial rotor position of the sensorless vector controller, it can not be used during start-up, due to inaccuracies of predicting rotor position at zero speed. This leaves either the partial and delayed open-loop scalar control scheme or the closed-loop scalar control scheme to be the most viable start-up control schemes; as both control schemes offer comparably low start-up times, start-up currents and voltage boosting; which will consequently affect the dimensioning of the transformer. The vector controller can then be implemented after the start-up procedure using the selected scalar control scheme, in order to obtain the optimal controller performance.

Controls and operation of variable frequency drives

Abstract: Unique apparatuses, methods, and systems of opposing, limiting, and/or preventing undesired or un-commanded compressor rotation are disclosed. One exemplary embodiment is an HVACR system comprising a variable frequency drive configured to drive an electric motor to rotate a screw compressor or scroll compressor. A controller is configured to monitor various aspects of the system and to control the drive. When a condition indicative of potential undesired or un-commanded compressor rotation is identified, the controller commands the variable frequency drive to control the motor to limit and preferably prevent compressor rotation. One technique comprises shorting switches of the drive to a DC bus rail to allow back EMF induced current in the motor windings to be dissipated through winding resistance thus providing a damping force. Another technique comprises controlling the inverter to insert a DC current into the motor to cause the motor to align to and hold a particular position.

Modeling of Bearing Capacitance and Resistance in Motor Bearing Current Problem

Abstract: The bearing current problem affects operation safety of the PWM variable frequency drive system. Precise calculations of capacitance parameters of bearings are very important to predict the shaft voltage and the bearing current. Combined with the elastic deformation and fluid mechanics analysis,the formula of thickness of the grease film and the Hertz contact area between balls and bearing races were obtained, then the bearing capacitance calculation model was derived. The relationships between the bearing capacitance and temperature,force and speed of the motor were analyzed. The equivalent bearing breakdown resistance calculation model was developed. The model shows that the resistance decreases with the rising of the breakdown numbers. The shaft voltage and the common voltage of a 2.2 kW induction motor fed by a PWM inverter were measured. The results verify the proposed model is reasonable.

Frequency converter special for air compressor and air compressor variable-frequency drive control system

Abstract: The invention provides a frequency converter special for an air compressor and an air compressor variable-frequency drive control system. The frequency converter special for the air compressor comprises a temperature detection circuit, a pressure detection circuit, an external fault detection interface and a control circuit. The frequency converter special for the air compressor is provided with the temperature detection circuit, the pressure detection circuit and the external fault detection interface, and hardware support is provided for the frequency converter special for the air compressor to integrate functions of an air compressor controller. As the frequency converter special for the air compressor integrates the functions of the air compressor controller, a special air compressor controller is not required to communicate with the frequency converter, the complicated parameter configuration process and the condition that the frequency converter is incompatible are avoided, the special frequency converter controller is omitted, the wiring of the air compressor variable-frequency drive control system is reduced, the system integration degree is improved, and the system is convenient to debug, mount and maintain.

Cycle-by-cycle current-limiting protection circuit for variable-frequency drive

Abstract: The utility model discloses a cycle-by-cycle current-limiting protection circuit for a variable-frequency drive. The circuit comprises a Hall sensor for converting a three-phase output current into a three-phase voltage signal, a three-phase full-bridge rectifier, an operational amplifier and a first comparator. The three-phase voltage signal is rectified by the three-phase full-bridge rectifier to generate a common-cathode voltage signal and a common-anode voltage signal. The common-anode voltage signal is electrically connected to an in-phase input terminal of the operational amplifier, and the common-cathode voltage signal is electrically connected to an anti-phase input terminal of the operational amplifier. An output terminal of the operational amplifier outputs a quasi-overcurrent signal. The quasi-overcurrent signal is electrically connected to an anti-phase input terminal of the first comparator, an in-phase input terminal of the first comparator is connected to a reference voltage, and an output terminal of the first comparator outputs a cycle-by-cycle current-limiting enabling signal. According to the utility model, when the current of the variable-frequency drive reaches a quasi-overcurrent point, the current is limited by hardware, such that the variable-frequency drive can work stably without faults under the conditions of short acceleration time and large compact load.

Optimization design of high efficiency variable frequency induction motor based on finite element analysis

Abstract: According to statistics, in the worldwide, industrial electricity consumption accounts for about 70% of the total consumption. The power consumption of the motor drive system is about 60%∼70% of the total industrial electricity consumption. When using variable frequency drive system, energy saving effect of the system is up to 20%∼40%, High efficiency design of variable frequency induction motor is conducive to improve energy-saving effect of the whole system. In this paper, a 55kW variable frequency induction motor was analyzed as an example. Based on the analysis of the composition and main influence factors of motor loss, optimize the design of the motor slot type and winding type. Propose an efficient design method of variable frequency induction motor. A prototype was made and the test results verified the design method is right.

Electro-Assist Turbo for Marine Turbocharged Diesel Engines

Abstract: Turbocharged diesel engines are widely used in the marine industry and have a significant impact on global CO2 and NOx emissions. Turbochargers are an integral component of any diesel engine and they play a critical role in their performance. Mitsubishi Heavy Industries (MHI) and Calnetix Technologies have developed a unique technology called the “Electro-Assist Turbo” (EAT). The EAT unit consists of a specially designed high speed permanent magnet motor directly mounted to the turbocharger rotating assembly. The high speed motor applies torque to the turbocharger rotor enabling it maintain or vary rotor speed at low engine exhaust flow rates in order to supply sufficient charge air to maximize engine performance. Turbocharged diesel engines suffer from inherent deficiencies at low engine speeds; there is not enough energy in the exhaust to produce an optimum and readily available level of boost for the engine intake air system at off-design points. This technology proves even more important as the majority of large marine vessels are now operating in a “slow steaming” part throttle mode. To date the majority of marine diesel engines use auxiliary air blowers (AAB) to supply additional air to the engine intake during off design point operation. These AABs are inefficient and not intended nor designed to be used in constant operation. The EAT unit can provide a higher discharge pressure at the same electrical power consumption as an AAB. This more efficient design with higher discharge pressure further improves fuel efficiency and eliminates the need to run an external piece of machinery during operation, thus lowering maintenance costs.This paper will provide an overview of the design, integration and initial testing of the 100kW Electro-Assist Turbo into a Mitsubishi Exhaust-gas Turbocharger (MET)-83 marine diesel turbocharger. In addition this paper will go over the custom designed aerodynamic motor housing structure that holds the non-rotating components without penalizing performance of the turbocharger, special software developed for the variable frequency drive system that enables the flexible operation of the high speed motor, and features of the high speed permanent magnet motor that allows for operation without any active cooling. Also, this paper will provide and discuss the initial test results of the EAT integrated into the MET-83 turbocharger along with engine testing results provided by MHI. Low cost designs will be discussed that enable turbochargers currently in operation to be retrofitted and the further improvements taking place to commercialize.Copyright © 2014 by ASME

Starter/generator combination with all variable frequency drives

Abstract: A gas turbine engine includes a compressor, a combustor adjacent the compressor, a turbine adjacent the combustor, a shaft, a motor, a primary variable frequency drive, an auxiliary variable frequency drive, and an auxiliary motor. The motor is coupled to the shaft. The primary variable frequency drive is electrically connected to the motor and an AC power source. The auxiliary variable frequency drive is electrically connected to the primary frequency drive. The auxiliary motor is electrically connected to the auxiliary variable frequency drive.

Dynamic simulated motor

Abstract: A controller is configured to generate control signals to control a variable frequency drive coupled with a load. A simulator receives the control signals and processes the control signals. The simulator simulates a variable frequency drive and a load by generating feedback signals based on a model and the control signals. The controller receives the feedback signals from the simulator.

PLC and Fuzzy Logic Control of a Variable Frequency Drive

Abstract: This work deals with the control of a VFD which acts as an intermediary between a three-phase induction motor and the PLC. The induction motor drives a conveyor belt which has three proximity sensor inputs. The first sensor gives the signal for motor to move in the forward direction, the second sensor halts the conveyor for a pre-defined period of time and the third sensor gives the signal for motor to move in the reverse direction. The PLC takes these inputs from the sensors and takes an appropriate action based on the logic developed for the motor control. Finally, the PLC output then becomes the VFD input, which after being reprocessed within the drive brings about the necessary control of the motor with respect to speed and position. In addition, Fuzzy Logic has also been applied to the system so that it can be trained to predict a reasonable output for even those inputs which were not foreseen by the network, therefore making the system flexible and easy to predict the result for various operating conditions. Keywords—VFD, PLC, RS-Logix, Ladder Logic Programming, Fuzzy Logic Controller.

Energy conservation in automatic fluid flow control using variable frequency drive

Abstract: The Pumping systems account for nearly 20% of the world’s electrical energy demand and range from 25-50% of the energy usage in certain industrial plant operations Pumping systems consume a significant portion of the electricity. Actual energy savings will vary greatly depending on how the discharge pressure of the constant speed pump is controlled and how it is operated after the VFD is installed. In the present work, the flow of pump has been controlled by two different methods, simulation work has been carried out and comparative statement is given. In this paper MATLAB simulink is use to show the performance of energy conservation in automatic fluid flow control using VFD.

Application of multi-function motor protection relays to variable frequency drive connected motors

Abstract: This paper reviews the application of multi-function motor protection relays to motors that are connected by variable frequency drives (VFD). Typical VFD internal motor protection functions are reviewed to understand the required roles of external motor protection relays. Applications discussed include protection requirements when the relay is located on the source side of the VFD and the motor side of the VFD. The impact of using a bypass switch around the VFD on protection requirements is also discussed.

Apparatuses, systems, and methods of variable frequency drive operation and control

Abstract: An exemplary system includes a compressor, a condenser, an expander, and an evaporator fluidly coupled to form a vapor-compression circuit, and an electric motor configured to drive the compressor. An inverter having a plurality of switching elements is configured to provide an output voltage to the electric motor through operation of the switching elements. A waste heat recovery circuit is configured to transfer waste heat from the inverter to a load. A controller is configured provide switching commands to the switching elements of the inverter. The controller is further configured to sense a condition of the system, determine a heat production requirement based at least in part upon the system condition, and to vary the number of switching commands per unit time based at least in part upon the heat production requirement.

Speed Control of Three Phase Induction Motor by Variable Frequency Drive

Abstract: The PWM inverter is controlled to produce a desired sinusoidal voltage at a particular frequency, which is filtered by the use of an inductor in series and capacitor in parallel and then through squirrel cage induction motor.

System for operating a three-phase variable frequency drive from an unbalanced three-phase or single-phase ac source

Abstract: A variable frequency motor drive comprises a converter including a rectifier having an input for connection to an AC power source and converting the AC power to DC power. A DC bus is connected to the rectifier circuit. At least one bus capacitor is across the DC bus. An inverter receives DC power from the DC bus and converts the DC power to AC power to drive a motor. A controller is operatively connected to the converter. The controller comprises a speed control controlling the inverter responsive to a speed command to maintain a desired motor speed. A speed foldback control measures DC bus ripple voltage and regulates the speed command responsive to the measured DC bus ripple voltage.

Power quality improvement of PMSG based DG set feeding 3-phase 3-wire load

Abstract: This paper presents power quality improvement of PMSG (Permanent Magnet Synchronous Generator) based DG (Diesel Generator) set feeding a 3-phase 3-wire load using STATCOM (Distribution Static Compensator). A 3-leg VSC (Voltage Source Converter) with a capacitor on the DC link is used as STATCOM. The reference source currents for the system are estimated using a Adaline based control algorithm. A PWM (Pulse Width Modulation) current controller is using for generation of gating pulses of IGBTs of three leg VSC of the STATCOM. The STATCOM is able to provide voltage control, harmonics elimination, power factor improvement, load balancing and load compensation. The performance of the system is experimentally test on various types of loads under steady state and dynamic conditions. A 3-phase induction motor with variable frequency drive is used as a prototype of diesel engine with speed regulation. So, the DG set is run at constant speed so that frequency of supply remains constant irrespective of loading condition.

Automated system to determine variable frequency drive skip frequency bands for vibration control

Abstract: A vibration control system for a variable speed cooling system includes a programmable controller in communication with a variable frequency drive (VFD). The programmable controller is programmed to command the VFD to operate at frequencies only outside of one or more frequency lockout bands automatically calculated by the programmable controller based on a comparison of newly acquired variable speed cooling system vibration data with previously stored variable speed cooling system vibration specification data.

Pressure control system of the pumping units with frequency-controlled induction motor

Abstract: The ever-increasing demands to the quality of production processes are associated with the pumping of non-viscous liquids, which indicate the need in improving operating conditions of liquid transfer systems with centrifugal pumps, including by means of mathematical modeling. The purpose of the paper is to develop a system for stabilizing the pressure in the calculated point by a scalar frequency-controlling of an induction motor speed, and to study its dynamic operation modes. The following methods are used in the research: theory of the variable frequency drive and electrical machines, methods of operational calculus, theory of centrifugal bladed machines. As a result, a scheme for controlling the pressure of the centrifugal pumping unit in the calculated point by controlling the rotational speed of the induction motor and determining calculated pressure indirectly using the respective models of the centrifugal pump was developed.

The Influence of Main Pump with High-Voltage Variable Frequency Drives on Electric Motors Periodic Repair

Abstract: The main objective of the work - to investigate the effect on the wear of high voltage electric motors of main pump units periodic switching on and off in cyclical pumping. Frequent starts motors in a cyclic pumping lead to accelerated wear of the mechanical parts of the motor due to the impact of dynamic loads at start-up, as well as winding insulation due to high inrush currents flow. As a result of accelerated depreciation may decrease residual life, overhaul period and service life of electric motors. The main factor affecting the service life of insulation motors are winding temperature, and as a consequence, the thermal aging of the insulation. The use of variable frequency drive can significantly reduce the cyclic transfer modes, or even eliminate them. The authors obtained analytical expressions for the evaluation of insulation deterioration at the start of the motor, which allow us to study the impact of the following factors: insulation class, the start time, break time at work, initial and nominal temperature, the temperature rise of the windings over the ambient temperature. The effect on the deterioration of the insulation cold start and hot conditions, as well as the percentage of the hottest start-ups in the total number of starts. Obtained expressions for the depreciation of isolation to determine the change timing of overhauls of high voltage electric main pump units. The developed method was approved by the example of the use of a variable frequency drive on the oil pumping stations construction section Leninsk-Nurlino trunk pipeline Nizhnevartovsk - Kurgan - Kuibyshev. The analysis showed that the installation of a variable frequency drive motors on three main pump units technological area of the number of starts to decline by 14%. The results can be used for pipeline transport of oil companies when planning the timing and costs of the current and capital repairs of high voltage electric motors main pump units.

Diagnostics for systems including variable frequency motor drives

Abstract: One embodiment is a diagnostic method for a system including setting a first diagnostic code based upon a condition of a DC bus of a variable frequency drive during a first drive state, setting at least one additional diagnostic code based upon a condition of at least one motor phase current during a second drive state, outputting first diagnostic information indicating a malfunction of the variable frequency drive if the first diagnostic code indicates a first error, and outputting second diagnostic information indicating a malfunction of a motor or a connector coupling the motor and the drive if the at least one additional diagnostic code indicates a second error.