Showing papers on "Variable-frequency drive published in 2015"

A Systematic Power-Quality Assessment and Harmonic Filter Design Methodology for Variable-Frequency Drive Application in Marine Vessels

Abstract: In maritime industry, high fuel costs encourage use of variable-frequency drives (VFDs) for energy-saving applications. However, introduction of such nonlinear loads in the vessel's power distribution network induces harmonics, which can lead to potential risks if are not predicted and controlled. In this paper, a systematic power-quality assessment and monitoring methodology is proposed to calculate VFD contribution to voltage distortion at the point of common coupling (PCC), considering the source short-circuit capacity and the existing vessel's power system harmonics. According to voltage harmonic distortion limits set by marine classification societies, design and sizing of appropriate harmonic attenuation filters is made, including ac and dc chokes and frequency-tuned passive filter options. The effectiveness of the proposed power-quality analyzing procedure is evaluated through a real practical example, which includes harmonic filter design for VFD retrofit application to fan and pump motors that operate constantly during sea-going operation in a typical tanker vessel. Power-quality field measurements obtained through a harmonic monitoring platform implemented on board verify that total voltage harmonic distortion and individual voltage harmonics at PCC are maintained below 5% and 3%, respectively, showing that design complies with relevant marine harmonic standards even in the worst operating case.

Energy Savings Potential for Pumping Water in District Heating Stations

Abstract: In district heating stations, the heat carrier is circulated between the energy source and consumers by a pumping system. Fluid handling systems, such as pumping systems, are responsible for a significant portion of the total electrical energy use. Significant opportunities exist to reduce pumping energy through smart design, retrofitting, and operating practices. Most existing systems requiring flow control make use of bypass lines, throttling valves or pump speed adjustments. The most efficient of these options is pump speed control. One of the issues in using variable-speed pumping systems, however, is the total efficiency of the electric motor/pump arrangement under a given operating condition. This paper provides a comprehensive discussion about pump control in heating stations and analyzes the energy efficiency of flow control methods. Specific attention is also given to the selection of motor types, sizing and pump duty cycle. A comparative energy analysis is performed on the hot water discharge adjustment using throttling control valves and variable-speed drives in a district heating station constructed in Romania. To correlate the pumped flow rate with the heat demand and to ensure the necessary pressure using minimum energy, an automatic system has been designed. The performances of these control methods are evaluated in two practical applications. The results show that approximately 20%–50% of total pumping energy could be saved by using the optimal control method with variable-speed pumps. Additionally, some modernization solutions to reduce the environmental impact of heating stations are described.

Variable frequency drive self-check

Abstract: Diagnostic and/or control methods, systems and apparatuses for variable frequency drives are disclosed. The variable frequency drive may be controlled by a controller that may conduct one or more tests or evaluations. The tests or evaluations may include determining whether a switching device in the variable frequency drive is open-circuited, short-circuited, or operating normally. The tests may include determining whether current provided at an inverter output of the variable frequency drive is within a predetermined range. An exemplary embodiment evaluates the drive for a short circuit condition, an open circuit condition, and a sensor error or failure condition, controls operation of the drive based upon these one or more evaluations, may abort operation of the drive based upon one or more evaluations, and may set a fault code indicative of the type of error encountered.

A variable-frequency electric drive with power supply by two independent inputs

Abstract: Excessive sensitivity to interruptions of power supply is a disadvantage of variable frequency drives: short-term power cutoffs or voltage depressions. Within the period of integration of the frequency changing circuit at essential units of a thermal power stations, this can result in increasing risk of electrical power unit blackout. To compensate for this disadvantage, variable frequency drives with electrical supply from two independent inputs have been developed. A frequency-changing circuit with two rectifiers connected on the direct current side has been taken as the basic one. To prevent uncontrolled switching over between inputs, priority of one input should be provided. In this case, increasing the voltage on the input that has been taken as primary is not an efficient solution. Continuous operation of the electric drive should be provided with automatic switching over the reserve input at the loss of supply voltage on the primary input. We propose an arrangement based on two groups of identical frequency-changing circuits connected in parallel on the direct current side. The arrangement also contains a voltage adjuster equipped with an automatic control system, which must provide steady operation of the electric drive with primary input supply. The power unit of the adjuster is constructed based on the active field-bus module (ALM) realized on fully controllable switch contacts. A frequency drive with a simplified main circuit and with a diode rectifier and a group of the active field-bus module ALM has been developed. To carry out experimental investigations of its modes, an experimental prototype of an electric drive with a fast response STATCOM model voltage (power) switch converter has been developed and manufactured. This converter acts as a voltage adjuster of ALM. Experimental investigations of the electric drive with simulation of blackout on one of the inputs and gradual voltage load transfer between inputs and other modes have been conducted. The oscillograms of the main coordinates have been presented. It is shown that the required quality of the transient phenomena is provided in all modes. Thus, automatic switching of the frequency changing circuit over the reserved input practically has no effect on the operation of the electric drive. Thus, we can draw the conclusion that the technological mode of the basic unit will not be affected. Generally, experimental investigations have confirmed that steady operation is maintained of the variable frequency drive under conditions of voltage changes or switching off one of the inputs.

Variable Frequency Drive

Abstract: ‘Design Requirements Manual (DRM) News to Use’ is a monthly ORF publication featuring salient technical information that shou ld be applied to the design of NIH biomedical research laboratories and animal facilities. NIH Project Officers, A/E’s and other consultants to the NIH, who develop intramural, extramural and American Recovery and Reinvestment Act (ARRA) projects will benefit from ‘News to Use’. Please address questions or comments to: ms252u@nih.gov

Variable-frequency drive

Abstract: The utility model relates to the technical field of frequency conversion, and specifically relates to a variable-frequency drive. The variable-frequency drive comprises a variable-frequency drive shell, the outside of the variable-frequency drive shell is wrapped by a water cooling layer, circulation pipelines are arranged in the water cooling layer, one side of the variable-frequency drive shell is provided with an air inlet, a plurality of fans are arranged at the air inlet, and the variable-frequency drive shell is also provided with an air outlet. According to the variable-frequency drive, the problem of heat radiation of the variable-frequency drive in the prior art is solved, and the effect of heat radiation of the variable-frequency drive is better via the combination of air cooling and water cooling.

Variable frequency drive control system with no electrolytic capacitor, and control method

Abstract: The invention relates to a control method for a variable frequency drive control system with no electrolytic capacitor, and the method comprises the steps: collecting a network side phase angle and real-time currents of any two phases of a three-phase power supply of a motor; carrying out the Clark conversion and Park conversion of the real-time currents, and obtaining an alpha-axis current, a beta-axis current, a d-axis real-time current, and a q-axis real-time current; calculating a given q-axis current and a given d-axis current; calculating a d-axis error current and a q-axis error current, carrying out the error adjustment of the d-axis error current and the q-axis error current, and obtaining a given d-axis voltage and a given q-axis voltage; carrying out the Park conversion of the given d-axis voltage and the given q-axis voltage, and obtaining a given alpha-axis voltage and a given beta-axis voltage; carrying out the pulse width modulation of an inverter, and controlling the motor through the inverter. The method can achieve the high-speed running of the motor in a weak magnetic region, can optimize the phase currents of the motor while obtaining a high power factor of a network side, improves the system reliability, is simple and effective in control, and is suitable for the field of household appliances.

High-performance complex controller for high-power converters with low pulse ratios

Abstract: For high-power converters with low pulse ratios (e.g. 80 Hz load frequency with 600Hz carrier frequency for a 27 MVA Variable Frequency Drive), the current control loop design has been a challenge due to the large signal delay and potentially higher-order plant (LCL filter between the converter and machines). The stability issue and cross-coupling effect is a problem in such application. In this paper, a complex current controller with excellent dynamic performance is proposed. The design is done by using the “double-sided frequency modeling” methodology. The stability, decoupling-effect, dynamic response and the robustness of the control loop are analyzed, which provides a design guideline for such applications. The performance of the proposed strategy and the improved state feedback method are compared. And finally simulation results are presented to validate the controller design and analysis.

Energy conservation using variable frequency drives of a humidification plant in a textile mill

Abstract: Humidification plant in a textile industry is one of the major power consumers due to its continuous operation for maintaining required Relative Humidity (RH) and temperature of spinning plant to increase the quality of yarn The traditional method of operation of induction motors in humidification plant was effective, but not energy efficient To overcome this problem, the emerging trend is the widespread adoption of variable frequency drives (VFD) which can offer potential energy savings in a system by allowing continuous process of speed control In this paper, modeling, simulation and performance analysis of ‘Open loop and closed loop speed control of induction motor using Variable frequency drive’ in MATLAB/Simulink and the Performance Verification of humidification plant in a textile industry where VFDs are installed very recently are presented

Variable frequency drive circuit with overvoltage protection

Abstract: A variable frequency drive (VFD) circuit includes an input connectable to an AC source, a rectifier to convert an AC power input to a DC power, a DC link to receive DC power from the rectifier and having a DC link voltage thereon, a DC link capacitor bank with one or more capacitors connected to the DC link, and a pre-charge circuit coupled to the DC link capacitor. The pre-charge circuit further includes one or more resistors, one or more pre-charge relays each operable in on and off states to selectively control a current flow through the resistor(s) so as to control an initial pre-charge of the DC link capacitor, and an overvoltage relay operable in on and off states to selectively cut-off a current flow to the DC link capacitor bank, so as to prevent an overvoltage condition in the DC link capacitor bank.

Motor fault diagnosis using higher order statistical analysis of motor power supply parameters

Abstract: Motor current signature analysis (MCSA) has been an effective method to monitor electrical machines for many years, predominantly because of its low instrumentation cost, remote implementation and comprehensive information contents. However, it has shortages of low accuracy and efficiency in resolving weak signals from incipient faults, such as detecting early stages of induction motor fault. In this thesis MCSA has been improved to accurately detect electrical and mechanical faults in the induction motor namely broken rotor bars, stator faults and motor bearing faults. Motor current signals corresponding to a healthy (baseline) and faulty condition on induction motor at different loads (zero, 25%, 50% and 75% of full load) were rearranged and the baseline current data were examined using conventional methods in frequency domain and referenced for comparison with new modulation signal bispectrum. Based on the fundamental modulation effect of the weak fault signatures, a new method based on modulation signal bispectrum (MSB) analysis is introduced to characterise the modulation and hence for accurate quantification of the signatures. This method is named as (MSB-SE). For broken rotor bar(BRB), the results show that MSB-SE suggested in this research outperforms conventional bispectrum CB significantly for all cases due its high performance of nonlinear modulation detection and random noise suppression, which demonstrates that MSB-SE is an outstanding technique whereas (CB) is inefficient for motor current signal analysis [1] . Moreover the new estimators produce more accurate results at zero, 25%, 50%, 75% of full load and under broken rotor bar, compared with power spectrum analysis. Especially it can easily separate the half BRB at a load as low as 25% from baseline where PS would not produce a correct separation. In case of stator faults, a MSB-SE is investigated to detect different severities of stator faults for both open and short circuit. It shows that MSB-SE has the capability to accurately estimate modulation degrees and suppress the random and non-modulation components. Test results show that MSB-SE has a better performance in differentiating spectrum amplitudes due to stator faults and hence produces better diagnosis performance, compared with that of power spectrum (PS). For motor bearing faults, tests were performed with three bearing conditions: baseline, outer race fault and inner race fault. Because the signals associated with faults produce small modulations to supply component and high noise levels, MSB-SE is used to detect and diagnose different motor bearing defects. The results show that bearing faults can induce detectable amplitude increases at its characteristic frequencies. MSB-SE peaks show a clear difference at these frequencies whereas the conventional power spectrum provides change evidences only at some of the frequencies. This shows that MSB has a better and reliable performance in detecting small changes from the faulty bearing for fault detection and diagnosis. In addition, the study also shows that current signals from motors with variable frequency drive controller have too much noise and it is unlikely to discriminate the small bearing fault component. This research also applies a mathematical model for the simulation of current signals under healthy and broken bars condition in order to further understand the characteristics of fault signature to ensure the methodologies used and accuracy achieved in the detection and diagnosis results. The results show that the frequency spectrum of current signal outputs from the model take the expected form with peaks at the sideband frequency and associated harmonics.

Controller for motor

Abstract: A controller is provided which can interface with a variable frequency drive and a motor, the controller having (a) one or more voltage and current sensors which can interface with a power line linking the variable frequency drive and the motor; and (b) a signal interface module which can receive electrical signals associated with an operating condition of the motor from the one or more voltage and current sensors. The signal interface module can correlate the received electrical signals with a rotor position of the motor, and transmit signals corresponding to rotor position, to the variable frequency drive. The data provided by the controller if conveyed as a rotor position, may cause the variable frequency drive to change one or more of its operating parameters to maintain proper synchronization of the rotor and its associated stator currents. Alternatively, the controller may directly control variable frequency drive operating parameters.

Energy conservation using VFD

Abstract: The AC induction motors converts the electrical energy into mechanical and other usable forms. Therefore, for this purpose about two third of the electrical energy is fed to motors in world. So energy conservation for motors is the major constraint. And this energy conservation is achieved by using variable frequency drive at some extent. Generally, there are three types of major load applications classified as 1. Variable torque type load 2. Constant torque type load 3. Constant Horsepower type load This paper about variable frequency drive for 3 phase AC Induction motor and energy conservation achieved using Variable frequency drive for different types of loads.

A laboratory stand for research concerning drive units applied in unmanned flying micro vehicles

Abstract: This article presents a laboratory stand used for research concerning static and dynamic characteristics of MAV (micro air vehicle) drive units. An electric powered drive unit, applied in unmanned flying vehicles of short range was chosen as the research object. Such device consists of the following elements: acquisition and control unit, a variable frequency drive (VFD), an engine and a propeller. The article contains a description of the stand structure as well as the way of data acquisition and an example of its processing in the post-processing mode. Moreover, example tests and the results are presented here.

Dual motor drive for electric submersible pump systems

Abstract: An electric submersible pump (ESP, 22) control system (36) includes a primary variable frequency drive (VFD, 38), a transformer (42), and a secondary VFD (44). The primary variable frequency drive (VFD) is configured to receive power from a power source (34) and output a variable voltage and variable amplitude AC voltage. The transformer has a low voltage side and a high voltage side of the transformer. The primary VFD is coupled to the low voltage side. The transformer is configured to receive the AC voltage from the primary VFD and output a stepped up AC voltage. The secondary VFD is coupled to the high voltage side of the transformer, wherein the secondary VFD is configured to provide a supplemental voltage in addition to the stepped up AC voltage when the operational values of an electric motor (30) exceed a threshold value.

Common-mode voltage measuring method for frequency converter

Abstract: The invention discloses a common-mode voltage measuring method for a frequency converter. Common-mode voltage test is carried out based on a central point on the input side of the frequency converter as a reference point according to the definition of frequency converter common-mode voltage. Compared with a traditional testing method which takes a central point on the DC side of the frequency converter and a system grounding point as reference points, the method provided by the invention is simpler and more convenient in measurement and easy to realize. Meanwhile, according to the invention, by constructing a variable frequency drive system circuit, experimental analyses on the waveform of the common-mode voltage of the frequency converter are performed under the three conditions that the system grounding point is taken as the reference point, the central point on the DC side of the frequency converter is taken as the reference point and the central point on the input side of the frequency converter is taken as the reference point; and the experimental analyses prove that the common-mode voltage measuring method which takes the central point on the input side of the frequency converter as the reference point is easier to realize, can more accurately reflect the common-mode voltage of the whole frequency converter and has very good guiding significance in inhibiting the common-mode voltage of the whole frequency converter.

Networked control of single-phase induction motor air conditioners for constrained power systems

Abstract: Split-Type Air Conditioners (ACs) are extensively used in households, commercial organizations and industrial setups. The duty-cycle based hysteretic control is inefficient and requires high power provisioning of full startup current for the compressor at each turn-on. This is especially demanding in constrained power systems with weak grids where people are dependent on backup generators and UPS for power needs during load-shedding. Some work has been done on optimizing energy consumption of Split-type ACs based on DC Compressors e.g. permanent magnet brushless DC motors (PMBLDCM) and three-phase induction machines but limited work has been done on operational optimization and energy efficiency of Split-type ACs based on single phase permanent split capacitor induction motors (SPPSCIM). This paper presents a networked Variable Frequency Drive (VFD) for these ACs to optimize operation, enhance energy efficiency and increase load drive capability of constrained energy systems. The network mode of operation allows existing installed base of standalone units to be integrated with central control infrastructure in an organization through Building Management Systems (BMS). The drive is designed, and tested on a 2.3kW Mitsubishi Electric Split-type air conditioner with SPPSCIM. The results of implemented VFD with networked control over Wi-Fi are presented to validate the effectiveness of the speed drive and the enhanced capability enabled by networked operation.

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.

Methodic of calculation of the non-sinusoidal voltage index within electrical networks with high-voltage frequency convertors

Abstract: The paper gives the procedure for calculation of the voltage non-sinusoidality ratio of the electric mains supplying electric drives with high voltage frequency convertors. It includes the calculation charts which help to predict its value for the cases with six- or similar twelve-phase rectifiers and various relations of inductive impedance of the matching transformer (input reactor) and similar one of the electric supply system. The paper determines the ratio of short circuit power and variable frequency drive power providing specified values of the non-sinusoidality ratio for convertors with various rectification circuits. It considers activities providing electromagnetic compatibility of the power frequency convertors with the electric supply main. They include changes within the electric supply system structure, improvement of the frequency converter circuits and application of devices for changing the unified power quality index. It proves that it is more reasonable to raise the rectifier pulse number and apply the rectifier with pulse width modulation.

Variable frequency drive overvoltage protection

Abstract: Overvoltage protection apparatuses, systems and methods for variable frequency motor drives are disclosed. In an exemplary embodiment, a variable frequency motor drive system including a rectifier, a DC bus electrically coupled with the rectifier, and an inverter electrically coupled with the DC bus is provided. A protection device electrically coupled with the rectifier and configured to interrupt power supply to the system based upon fault conditions is provided. A controller is provided and configured to receive information indicative of a voltage of the DC bus, process the received information to model a condition of at least one component of the variable frequency motor drive, and control the protection device to interrupt power supply to the variable frequency motor drive if the modeled condition meets a fault criterion.

Control system for frequency conversion and electric control integrated plate

Abstract: The utility model relates to the frequency conversion and electric control technologies. Regarding the problem in the prior art that compressors of different models are required to be matched with frequency conversion and electric control integrated plates of different models, a control system for a frequency conversion and electric control integrated plate is provided. The control system comprises a human-machine interaction module, a storage module, a master control processing module, an optocoupler module, a variable frequency drive processing module, a drive circuit and a compressor. The human-machine interaction module is connected with the storage module and the master control processing module, the master control processing module is connected with the optocoupler module connected with the variable frequency drive processing module, and the variable frequency drive processing module is connected with the drive circuit connected with the compressor. The variable frequency part is controlled to call a control parameter of the corresponding compressor by setting the human-machine interaction module and inquiring the model of the compressor matched with a refrigerator to drive the compressor, so that the effect that the compressors of multiple models can be used by one type of control system for the frequency conversion and electric control integrated plate is achieved. The control system is applied to the control technology of the frequency conversion and electric control integrated plate.

MTBF comparison of cutting edge medium voltage drive topologies for oil & gas applications

Abstract: As process interruptions can be very expensive, reliability and availability values of a variable frequency drive (VFD) are often two of the most important requirements when selecting a drive. Reliability figures are hard to compare because methods and values depend on suppliers using different assumptions and definitions of failures. The main medium voltage VSI (voltage source inverter) topologies (3-level, 5-level, multilevel) for oil & gas applications will be compared with respect to their main power components (semiconductors, capacitors, PCBs, etc.) considering component stress and field data experience. The total reliability of these drive systems (including transformers, recooling unit, control cabinet) will be calculated using the same methods and assumptions.

Induction motor emulation for variable frequency drives testing

Abstract: This paper presents a method employing a simple three-phase transformer connected to a three-phase AC variable load for emulating a standard three phase AC induction motor. Such an emulator could be used for variable frequency drive testing but eliminates any moving parts for higher reliability, reduces audible noise, and eliminates high-cost dynamometers. The method utilizes the concept of assuming that the induction machine is a "rotating transformer." To validate the emulator behavior, a simulation for a line-fed machine and a line fed three-phase transformer with a three-phase variable load is performed. Experimental verification of the inverter-fed machine and transformer are also presented and show excellent emulation capabilities of motor behavior at various slip values.

Shunt active power filtering for smart appliances

Abstract: Due to the increasing trend towards energy saving white goods appliances and the commercial viability of power electronic components, there has been an expansion in the use of solid state electronics and variable frequency drive motors in these applications. However, a major drawback of using such energy efficient loads is the introduction of current harmonics onto the local distribution grid. Furthermore, the proliferation of such devices elevates the supply harmonic content and can potentially impact residential distribution networks. This paper investigates the harmonic content generated by some household appliances and suggests a solution to minimize harmonics by means of active filtering. An active filter circuit was simulated to compare filter performance when used as an active front versus a feeder input compensator.

Dynamical modeling of frequency controlled variable speed parallel multistage centrifugal pumps

Abstract: This paper presents a development of a model of a set of multistage centrifugal electro pumps including two 4 stage stainless steel centrifugal pumps, each coupled to a 4 kW three-phase induction motor, connected to a hydraulic application running under two control strategies including constant speed and variable speed methods. Each pump provides 16 m3/hr flow rate and 58mwater head at BEP (Best Efficiency Point). Dynamicity of the model causes variations in all operational parameters of pumping system in any variation on consuming flow rate. Each electro pump has been driven with a variable frequency drive utilizing frequency control method for adjusting the rotational speed under a PID control regarding to match of pumping system operational point with the consumption point to save the energy. 83% energy saving is achieved by model in variable speed control strategy comparing to constant speed control strategy. MATLAB/SIMULINK software using ode45 solver and variable step size simulates this model.

Fuzzy PID Temperature Control System Design Based on Single Chip Microcomputer

Abstract: In order to solve oil drilling crew's VFD (Variable Frequency Drive) room can't make air conditioning to cool the equipment problems cause of diesel generator fails suddenly stop power supply, this paper introduces the hardware and software design based on the constant temperature system of the STC89C52 SCM and carries out the simulation through MATLAB so as to compare and analyze the fuzzy self-turning PID control results and traditional PID control simulation results. The experimental results show that this design can realize the SCM constant temperature control of fuzzy PID algorithm.

Variable frequency speed control system and method of the same

Abstract: A variable frequency speed control system having a low voltage ride through function that includes a variable frequency drive having a rectifier, a DC bus and an inverter is provided. The variable frequency speed control system includes a voltage drop detecting module, a frequency control module, an operation mode selecting module and an inverter control module. The voltage drop detecting module generates a voltage drop coefficient according to a grid voltage and a rated grid voltage and generates an operation mode switching signal. The operation mode selecting module receives a target frequency signal and a frequency decreasing amount and generates an output frequency signal according to the operation mode switching signal. The inverter control module generates a three phase modulating signal according to the output frequency signal, which is used to control the operation of the inverter.

System and method for speed control of variable speed pumping systems

Abstract: A system and method for controlling a speed of a pumping system includes a controller, a variable frequency drive connected to the controller, a motor connected to the variable frequency drive, a pump connected to the motor, a set of sensors connected to the motor, the pump, and the controller, and an interface connected to the controller. The controller includes a processor and a memory connected to the processor. A motor control process is saved in the memory and executed by the processor that generates a motor control signal to control the speed of the motor and the pump.

Structural dynamics of a wind turbine drive train high speed subsystem: mathematical modelling and validation

Abstract: The paper studies the dynamics of a wind turbine drive train high speed subsystem, both by modelling and experiments with focus on system torsional vibration and transient events which can reduce fatigue life of functional components (gearbox, bearings, shafts, couplings, others). A scaled down drive train high speed shaft test rig has been developed. Main components of the test rig are six-pole motor with variable frequency drive controller (up to 1000rpm), shafts’ disk coupling and flexible mounting structure representing gearbox housing with output high speed bearing. The test rig is equipped with measurement system comprising a set of accelerometers and displacement sensors, strain gauges and telemeter system, data acquisition hardware and software (SKFWindCon3.0). Mathematical and computational models of the test rig have been developed and went through validation tests. The system dynamic response is studied for different operational scenarios and structural parameters (run-shut down case with and without eccentric mass). The ultimate goal of the test rig is to get insight into interaction between internal dynamics of drive train mechanical and electrical functional components and to develop novel methods to detect, predict and prevent faults and failures in wind turbine drive trains arising due to misalignments and transient external loads.