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The excitation system plays a critical role in the operation of synchronous generators. An equipment failure could impact the voltage quality for smaller grids. Furthermore, it can lead to cost penalties and reduced production for the power plant owner. Recently, a new high-speed-response rotating brushless exciter was developed that employs remote control of the rotating thyristors on the generator shaft. This has led to new possibilities for improving the performance of brushless exciters. This contribution investigates the failure modes of a dual-star outer pole exciter that feeds two separate thyristor bridges connected in parallel during a normal operation. The possibility of a redundant postfault operation due to open-thyristor or open-phase faults is demonstrated using experimental testing. The system is compared with the fault performance of a conventional three-phase system. This paper includes the implementation and validation of a fault-predicting double d–q exciter model. In addition, the dangerous effects of a shorted-thyristor fault are investigated. A “skip firing” protection technique is briefly demonstrated for the fast isolation of such faults, yielding nondestructive postfault recovery and redundant failure-mode operation. The evidence shows that the dual-star exciter is a competitive choice for the future development of fault-tolerant brushless exciters.

Brushless wound-rotor synchronous starter-generator (WRSSG) is drawing more and more attentions in aircraft power system applications because of advantages such as high safety and low cost in maintenance. Detailed analysis and optimal start control research for the WRSSG system need an accurate and time-efficient integrated model of WRSSG. Because of the presence of the rotating rectifier, there is a complex nonlinear relationship between electrical variables of the brushless exciter and main generator in WRSSG, which makes the building of the integrated model a very tough work. In this paper, an improved Parametric Average Value Model (PAVM) of the rotating rectifier with coefficients varying with load impedance and load current was proposed, and coefficients of the improved PAVM were obtained from simulations of the detailed joint Voltage-Behind-Reactance (VBR) model of WRSSG. Based on the improved PAVM of the rotating rectifier, an integrated model of the WRSSG with a two-phase brushless exciter was proposed in classic state-variable formulation. Computer studies verified that the proposed integrated model of the WRSSG is sufficiently accurate in simulations of both steady and transient states, and it is very computationally efficient compared with detailed switching models.

The static exciter is dominating among large grid-connected generators due to the weak dynamic performance of conventional brushless exciters. In this contribution, a six-phase double-star outer pole permanent magnet rotating brushless exciter is evaluated with different active rectification topologies. Both thyristor-based and chopper-based topologies are considered. A high speed response brushless excitation system is obtained by replacing the conventional rotating diode bridge rectifier with the proposed active rectification topologies on the shaft. The given two-stage system generates its own excitation power directly from the shaft, contrary to static exciters. The selection of an appropriate rectification topology could minimize the rotor armature phase currents for a given generator field current. The objective is a high-power factor and a high utilization of the exciter machine. An optimal rectification topology makes higher ceiling currents was possible, improving the transient behavior of the synchronous generator. In this paper, we show that six-phase topologies add complexity, but improve exciter redundancy, increase the available ceiling voltage, and reduce the steady-state torque ripple. Experimental results are given for validating the models implemented for the analysis.

Recent technological developments have caused a renewed interest in the brushless excitation system. With the application of wireless communication, the conventional diode bridge has been replaced with fully controllable thyristors on the shaft. It offers the same dynamic performance as the conventional static excitation system. The thyristor bridge of the conventional three-phase exciter needs to be controlled with a high firing angle in normal operation in order to fulfill a requirement of both a high ceiling voltage and a high ceiling current. A high firing angle causes high torque ripple to be absorbed by the exciter stator and a low power factor results in a low utilization of the designed exciter. In this contribution, we present a strategy that solves this problem by looking into combinations of thyristor configurations of a double-star six-phase connection of the exciter. Experimental results are used to verify the circuit models implemented for this investigation. A hybrid-mode 12-pulse thyristor bridge configuration seems to be a good solution for implementations in commercial apparatus. An additional switch interconnects two separate thyristor bridges from parallel- to series connection at the rectifier output, and utilizes the advantages of both topologies.

Brushless excitation systems are widely used for synchronous machines. As a critical part of the system, rotating rectifiers have a significant impact on the system behavior. This paper presents a numerical average-value model (AVM) for rotating rectifiers in brushless excitation systems, where the essential numerical functions are extracted from the detailed simulations and vary depending on the loading conditions. Open-circuit voltages of the brushless exciter armature are used to calculate the dynamic impedance that represents the loading condition. The model is validated by comparison with an experimentally validated detailed model of the brushless excitation system in three distinct cases. It has been demonstrated that the proposed AVM can provide accurate simulations in both transient and steady states with fewer time steps and less runtime compared with detailed models of such systems and that the proposed AVM can be combined with AVM models of other rectifiers in the system to reduce the overall computational cost.

Role of round rotor synchronous generator in renewable and sustainable energy is rapidly growing due to growing demand of energy production from the renewable resources. The less wear and tear, high robustness and accessibility to power electronics deployment (for active/reactive power flows from and to the grid) has increased the scope of round rotor synchronous generators across large onshore and offshore wind farms besides in hydro power plants. In many commercial power modeling softwares, like System Simulator for Engineering (PSS/E), it is quite difficult to write, access, test, evaluate and validate the built-in models. Therefore to avoid these problems and help the researchers in evaluating, testing, modifying, expanding and enabling the power equipment models as user written, it is important that the equivalent models are designed in an accessible and comparable design and simulation environment like Simulink. The work presented in this paper therefore addresses these issues and provide researchers the equivalent PSS/e models of generator, its associated governor and exciter designed and modeled in Simulink environment.

This paper develops a novel framework to design an optimal robust excitation system controller considering the uncertainties in the parameters of the model of the excitation system. The uncertainties may cause the parameter values to vary from their nominal values within a specified upper and lower limit. These uncertainties can have a significant influence on the dynamic characteristics of the power system, that is, the variations in the parameters of the excitation controller model due to the uncertainties in the parameters can cause the system to change from being stable to unstable. It is, therefore, important to design a robust excitation system controller that can ensure that irrespective of the values of the parameters within the boundary of the uncertainties, the power system will not have any variation from its stability. The proposed framework decomposes the uncertainties in the parameters of the excitation system model into two components: matched and unmatched. To eliminate the uncertainties from both components, a linear quadratic regulator problem is constructed to deal with the matched component, while an augmented control is used to cope with the unmatched component. The robustness of the resulting controller is verified using time-domain dynamic stability simulations of a single-machine test system and the IEEE 39-bus New England system.

Condition-based maintenance of electric generators have been gaining increasing importance due to the electricity demand and the criticality that this equipment represents to electrical power systems. In this context, this paper proposes a methodology and a system for detection and modeling of incipient failures in the components of internal combustion engine-driven generators based on Electrical Signature Analysis (ESA). The proposed methodology enables the detection of incipient faults both in the prime mover and in the coupled synchronous generator, only relying on measurements of the generator stator voltages and currents. The proposed ESA failure patterns are based on defined frequencies and the structural features of the machine, so they can be reproduced in a wide range of engine-generators sets. The main advantages of the proposed system are its low intrusiveness, feasible installation and cost efficiency. A scale model laboratory has been designed to simulate faults in a small diesel generator and apply the ESA methodology to detect these faults and obtain the failure patterns. Experimental results are presented to prove the effectiveness of the proposed methodology. The main results include the findings that exciter generator unbalance induces electrical unbalance components, exciter diode short circuit induces even harmonics, intake valve failure and piston ring failure induce multiples of rotation frequency components, and mechanical misalignment of the engine generator set induces multiples of half order speed frequency components on ESA. Moreover, the proposed prototype is installed at two large in-service internal combustion engine-driven generators and examples of signal analysis are provided.

This paper presents a time-domain method for multi-exciter random environment tests. Traditional random environment test theory has been formulated in the frequency domain, where an important step is taking the inverse of the frequency response function matrices (FRFMs). The accuracy of this inversion tends to be poor, particularly at frequencies near lightly damped resonances. The currently used control algorithms face difficulties in suppressing abnormal spectral lines caused by this inverse problem. In this paper, traditional formulations of the environment test are reformed, and the time-domain method is adopted; this results in a more precise inverse operation in environment tests. To achieve this, reference spectra are converted into time-domain response signals. The finite long driving signals are derived by the state-space method with estimated state vectors. During the process, the inverse of rank-deficient Toeplitz matrices are stabilized with truncated singular value decomposition (TSVD) to suppress all abnormally high-level components in the driving forces; thus, overall, the spectra lines produced by noise within the frequency band are filtered out. A numerical simulation of a single-axis random vibration test of a cantilever beam is conducted using the traditional frequency-domain procedure (FDP) and the proposed time-domain procedure (TDP). The response spectra generated by both procedures are tested by control algorithms, and the result shows that responses generated by the proposed TDP are more easily controlled. The conditions of stability for both the FDP and the TDP are also determined and introduced in the simulation. Moreover, a multi-axis vibration experiment further validates the effectiveness of the TDP.

Generally, PM machines are used as PMG pre-exciters in 3-stage brushless excitations systems. This paper presents the design, characterization, and prototyping of a rotating brushless PM exciter used in a proposed 2-stage excitation system for a synchronous generator. The proposed design reduces the number of components compared with conventional systems. A comparison with the state-of-the-art conventional excitation systems is given. The design of a fast-response, or high initial response, brushless exciter requires active rectification on the rotating frame, replacing the noncontrollable diode bridge. The objective was to construct an exciter with the capability of a 50 A output field current, as well as a high value of the available ceiling voltage and ceiling current. The final exciter was constructed to be fitted into an in-house synchronous generator test setup. A finite element model of the exciter was validated with experimental measurements. The exciter prototype is also compared with an alternative armature design with nonoverlapping single-layer concentrated windings, but with the same main dimensions. The paper includes a general design procedure suitable for optimization of PM brushless exciters that fulfill the requirements of their synchronous generators and the grid.

This study aims to analyze the failure mechanism and improve the structural design of a vibration-based energy harvester (VEH), which intends to replace or extend the service life of batteries for condition monitoring systems of high-risk structures such as railroad vehicles and wind turbines. The observation of a fractured VEH under service condition of high-speed railway vehicle reveals several cracks originating on the surface of the VEH. A vibration test in the laboratory, conducted by using an electromagnetic exciter, identifies the resonant frequency, displacement-frequency, and acceleration-frequency plots of the VEH. A comparison of the surface fractured during vibration testing with that under service condition indicates that the major failure mechanism is static brittle fracture. The failure critical location and stress states are identified through frequency response analysis. Several measures are recommended to prevent the failure of VEHs, including selecting materials and redesigning the moving component of VEH.

In operation, expansion, complication and modernization of electrical power systems one of the important task is stability provisioning. Automatic exciter controller (AEC) functioning in synchronous machine (SM), is one of the devices, allowing to perform this task. The article defines and illustrates the variety of tasks that is necessary to solve by the development of AEC algorithms, analysis of functioning and setting their parameters. New techniques, designed for solution of these tasks are presented. These techniques allow when setting the regulators: 1. Take into account the working conditions of SM. 2. Determine the region of stability for given sets of AEC channel coefficients. 3. Determine the optimal AEC parameters settings, providing the best damping of transient processes under various disturbances. 4. Visually present regulation setting results. Solutions of all the tasks are demonstrated by the example of the analysis of the functioning and the setting up DECS-400 controller operating in a test scheme, assembled with real-time simulator RTDS.

Rotor blades are among the most delicate components of modern wind turbines. Reliability is a crucial aspect, since blades shall ideally remain free of failure under ultra-high cycle loading conditions throughout their designated lifetime of 20–25 years. Full-scale blade tests are the most accurate means to experimentally simulate damage evolution under operating conditions, and are therefore used to demonstrate that a blade type fulfils the reliability requirements to an acceptable degree of confidence. The state-of-the-art testing method for rotor blades in industry is based on resonance excitation where typically a rotating mass excites the blade close to its first natural frequency. During operation the blade response due to external forcing is governed by a weighted combination of its eigenmodes. Current test methodologies which only utilise the lowest eigenfrequency induce a fictitious damage where additional tuning masses are required to recover the desired damage distribution. Even with the commonly adopted amplitude upscaling technique fatigue tests remain a time-consuming and costly endeavour. The application of tuning masses increases the complexity of the problem by lowering the natural frequency of the blade and therefore increasing the testing time. The novel method presented in this paper aims at shortening the duration of the state-of-the-art fatigue testing method by simultaneously exciting the blade with a combination of two or more eigenfrequencies. Taking advantage of the different shapes of the excited eigenmodes, the actual spatial damage distribution can be more realistically simulated in the tests by tuning the excitation force amplitudes rather than adding tuning masses. This implies that in portions of the blade the lowest mode is governing the damage whereas in others higher modes contribute more significantly due to their higher cycle count. A numerical feasibility study based on a publicly available large utility rotor blade is used to demonstrate the ability of the proposed approach to outperform the state-of-the-art testing method without compromising fatigue test requirements. It will be shown that the novel method shortens the testing time and renders the damage evolution with a higher degree of fidelity.

Diesel-Engine Driven Generators (DDGs) are a kind of distributed generation (DG) units and similar to other DGs, cause power quality disturbances in power system. Flicker is one of the most important power quality disturbances having bad effects on the sensitive loads. In DDGs, Inherent Torque Fluctuations (ITFs), Misfiring (MF) in various cylinders, Gearbox Tooth Crashing (GTC), governor and exciter errors in presence of the mentioned factors are some of the faults, which produce flicker. Therefore, it is necessary to recognize any faults causing flicker to prevent serious problem in DDGs. Also, identifying these factors is effective in accelerating process of repair and maintenance for DDGs. Therefore, in this paper firstly, all faults that cause flicker are modeled and simulated, then a pattern recognition method is presented for their detection. In the proposed method, Discrete Wavelet Transform (DWT) and Discrete S-Transform (DST) are used for feature extraction and Gram-Schmidt (GS) is used for feature selection. Afterwards, a classifier based on K-Nearest Neighbors (KNN) is used to detect the faults. Also, the impact of faults on flicker severity has been evaluated by short-term severity of flicker (Pst index).

In this paper a prototype clamped free beam novel energy harvester (NEH) was designed and demonstrated in detail by using CATIA V5 tool. And also it was tested on 20g electromagnetic exciter at different striking loads and under the frequency of 60 Hz by using lead zirconate titanate (PZT-5H) discs or patches or transducers or circular diaphragms. The recorded output power is 5.264 mW at 0.49 N load. 5.264 mW output power can be used for operating the low power devices such MEMS devices and electronic microprocessors.

An integrated starter/generator based on the wound-rotor synchronous machine is becoming increasingly popular in modern aircraft due to the advantages of high safety and low cost in maintenance. Constant field current for the main generator of the wound-rotor synchronous starter/generator (WRSSG) can simplify the start control scheme distinctly in the starting mode. In order to achieve constant field current for the main generator, three detailed excitation control methods for the two-phase brushless exciter of the WRSSG in the starting mode were proposed and compared in this paper. And in these excitation control methods, feedback control for the field currents of the two-phase brushless exciter and speed reference control for the excitation frequency and phase sequence were adopted. Simulation and experimental results verified the feasibility and effectiveness of these three excitation control methods.

With the increasing demand for the cleaner production of electric energy, many countries around the world strive to develop new turbo-generators with advanced parameters and large capacities. In the design of a new turbo-generator, it is important to optimize the anti-vibration performance of its key components in order to ensure its safe and reliable operation. The anti-vibration optimization of the key components in a turbo-generator when a set of alternative schemes are provided for selection is a heterogeneous multi-attribute decision making (HMADM) problem involving deviation attributes, which cannot be solved by present HMADM approaches. To solve such a HMADM problem, a novel heterogeneous axiomatic design (HAD) method is developed by introducing the distance measure into axiomatic design for computing the information contents of the alternative schemes. With the attribute data in various mathematical forms unified as triangular fuzzy numbers, their probabilities of success can be conveniently calculated by a unified formula once their corresponding positive and negative ideal solutions are determined. As a result, the complexity and computational cost involved in computing the information contents of alternatives can be greatly reduced, which enables the efficient solution of the HMADM problem involving deviation attributes. A case study on the fixture scheme optimization for the stator end windings in a large turbo generator demonstrated the feasibility and effectiveness of proposed HAD. The ninth fixture scheme with the structural manufacturability being very good (VG), the natural frequencies at the turbine and exciter ends being [68.2, 78.5]Hz and [72.5, 83.2]Hz, the maximum amplitudes at the turbine and exciter ends being 67 μm and 72 μm was chosen as the optimal scheme from nine alternatives according to the HMADM results.

A novel panel-form loudspeaker in which the panel of the speaker is excited by the forces generated through the flat voice coil of a rectangular electro-magnetic type exciter for sound radiation is presented. The exciter when properly designed has the advantage of exerting appropriate loads to the panel so that the major sound pressure level (SPL) dips of the speaker can be suppressed or even eliminated. For designing such panel-form speaker, a method formulated on the basis of the classical plate theory (CPT), Ritz method, and first Rayleigh integral is proposed for predicting the SPL curve of the speaker. An experimental investigation was performed to verify the feasibility of the proposed method. The effects of some system parameters on the major SPL dips of the proposed panel-form speakers are investigated by means of several numerical examples. The optimal locations of flat voice coils for exciting several panel-form speakers are determined to illustrate the important role of excitation location for enhancing sound quality of such speakers via the removal or suppression of the major SPL dips.

Electromagnetic testing is the most widely used technique for the inspection of steel wire ropes. As one of the electromagnetic detecting approaches, the magnetic flux leakage (MFL) method has the best effect for the detection of broken wires. However, existing sensors based on MFL method still have some problems. (1) The size of the permanent magnet exciter is usually designed according to experience or rough calculation, and there is not enough depth analysis for its excitation performance, (2) Since the detectable angular range for a single Hall component is limited, Hall sensor arrays are often employed in the design of MFL sensors, which will increase the complexity of the subsequent signal processing due to the extensive use of Hall components, (3) Although the new magneto-resistance sensor has higher sensitivity, it is difficult to be applied in practice because of the requirement of the micron-level lift-off. To solve these problems, a sensor for the detection of broken wires of steel wire ropes based on the principle of magnetic concentration is developed. A circumferential multi-circuit permanent magnet exciter (CMPME) is employed to magnetize the wire rope to saturation. The traditional Hall sensor array is replaced by a magnetic concentrator to collect MFL. The structural parameters of the CMPME are optimized and the performance of the magnetic concentrator is analyzed by the finite element method. Finally, the effectiveness of the designed sensor is verified by wire breaking experiment. 1&ndash, 5 external broken wires, handcrafted on the wire rope with a diameter of 24 mm, can be clearly identified, which shows great potential for the inspection of steel wire ropes.

When a hypersonic aircraft flies at a high Mach number, the plate-like attitude control structures, such as the wings and rudders, will be exposed to an extremely high-temperature environment. To obtain the thermal modal parameters of a structure that are difficult to measure, a high-temperature transient heating test system and a vibration test system were combined to establish a test system that can perform the thermal/vibration test at 1200 °C. Infrared radiation heating was employed to generate a controlled time-varying high-temperature environment, and an exciter was used to exert vibration excitation on the free end of the cantilever rectangular plate. A self-developed extension configuration of a high-temperature-resistant ceramic pole was used to transfer the vibration signals of the structure to a non-high temperature zone, and the acceleration sensors were applied to identify the vibration signals. The test data were analyzed using a time-frequency joint analysis technique, and next, the key vibration characteristic parameters of structure in a thermal-vibration coupled environment up to 1200 °C (e.g., the modal frequency and modal vibration shape) were experimentally obtained. In addition, the numerical simulation on the thermal modal characteristics of a rectangular plate was performed. The calculated results coincide favorably with the test results, verifying the credibility and effectiveness of the experimental methods. The research results can provide an important basis for the dynamic performance analysis and safety design of structure under high-temperature thermal-vibration conditions for hypersonic flight vehicles.

In the oil industry, drillstring can be used as a transmission medium to send downhole information via a modulated compressional acoustic wave. However, the accompanied reverberation is a major constraint in the transmission rate and distance because of the multipath fading caused by the heterogeneous drillstring. In combination with discrete Fourier transform-spread (DFT-S) mapping/demapping, high-power amplitude squeezing and DFT-based least squares channel estimation methods, an improved orthogonal frequency division multiplexing (OFDM) scheme is proposed in this paper to overcome the symbol interference inherent in the drillstring multipath channel and reduce the peak-to-average power ratio of the signal. Then an experimental rig is established by using a rotatable electromagnetic vibration exciter and a piezoelectric accelerometer arranged at the position closer to acoustic impedance terminal along a 6.3-m periodic simulated drillstring. The OFDM data sequences at a data rate of 200 bit/s over a limited bandwidth of 140 Hz are applied to the rotating simulated drillstring. The experimental results show that the proposed scheme using QPSK modulation can offer an error-free acoustic communication at rotation speeds up to 90 r/min.

In this paper, the implementation, characterization, calibration, and testing of a biaxial optical fiber accelerometer for vibration monitoring in three-phase induction motors is presented. The optical sensor uses fiber Bragg gratings to measure the displacement of an inertial mass relatively to a support base. The sensor characterization was measured through the impact hammer, allowing the determination of the natural frequencies in both sensitive directions, the values of 747.5 Hz and 757.5 Hz were estimated for the $x$ -axis and the $y$ -axis, respectively. For calibration, an electromagnetic exciter was used to introduce a controlled harmonic excitation at different frequencies, with this analysis, a high SNR was observed, on average over 30 dB for both sensitive directions, and a sensitivity of 100 pm x $\cdot \text{g}^{-1}$ was obtained, up to one third of the natural frequency, in each direction. The tests were developed with the main aim of the analysis in induction motors based in vibration monitoring, the analysis can help to prevent wear in motors, increasing its efficiency, and lowering maintenance costs. The optical accelerometer measurements were compared with the ones from a capacitive sensor, during regular operation and with a broken rotor bar operating with 75% and 100% load. The performed tests with the optical sensor allowed to successfully analyze the frequency components, and its changes, for the regular and damage operation.

This work proposes the generalization of models for excitation systems. Thirteen models according to IEEE standard are reduced to three main types by the development of a common universal excitation control model. The original IEEE division of exciter types into alternator-supplied rectifier and static excitation system is rearranged into non-controlled and controlled rectifier types. This division is suitable for model classification and for authors and users of network simulators. Proposed simplification may facilitate a data collection of dynamic models for studies of large power system.

This study proposes a novel mathematical model based on excitation system output equations (ESOEs) to evaluate the steady-state performance of the three-phase brushless asynchronous excitation system (BAES) of a wound-field synchronous aircraft starter-generator system. The steady-state performance could be used to evaluate the field current output capabilities of the BAES and provide a reference for the control schema of the BAES. However, the BAES has unknown multivariable non-linear characteristics, which give rise to difficulty in modelling the steady-state performance. Meanwhile, without closed-loop control of the main exciter stator current, the traditional methods fail to efficiently calculate the required excitation voltage and frequency for a desired field current. Steady-state performances are achieved for numerous discrete states with tedious simulations. This study develops the mathematical model of the ESOEs, which can be used to express the non-linear relationships among the main generator field current, main exciter (ME) rotor speed, ME excitation voltage, and frequency. The field current output capabilities could be evaluated in a time-efficient manner by solving these ESOEs. The proposed mathematical model and theoretical findings are verified by experimental results.

Expressions for vibration moments (additional dynamic loading caused by the vibrations of bearing body) during the passage of resonant zone by vibration machines with the flat vibrations of bearing body both with one arbitrarily located vibration exciter and with two self-synchronization vibration exciters for the different modes of starting are got in an analytical form. Possibilities of improvement of process of running approach of vibration machines with unbalanced vibration exciters are demonstrated by using of methods of the "double" (in case of one vibration exciter) and "separate" starting of electric motors (in case of two vibration exciters). It is shown that the first method is based on using of semislow vibrations arising in the resonant zone. The necessary condition of the successful using of this method is motion on the rotor of exciter in the moment of the repeated including of engine of rotary-type vibration moment. The conditions when the separate starting is effective are shown. Conclusions and practical recommendations that allow to facilitate starting of vibration machines with an unbalanced drive are pointed.

This paper presents a new general-purpose state-space synchronous machine model based on the voltage-behind-reactance (VBR) formulation which accounts for main flux saturation. The proposed model has a numerically efficient constant-parameter decoupled RL branch interfacing circuit comprised of the stator and field windings. Consequently, the new model can be interfaced directly with arbitrary power networks and exciter circuits. The presented studies, executed using the Simulink toolbox PLECS, demonstrate the superior combination of numerical accuracy and efficiency of the new VBR model compared with existing state-of-the-art models. As a result, the proposed model would be a desirable addition to the built-in component libraries of many industry-grade state-variable-based transient simulators.

This paper presents an elegant method for determining the simplest model of a power system electrical/mechanical load that will suffice for dynamic frequency power system studies and closed-loop simulation work. The strategy behind this technique is to supply the simplest load model possible that gives sufficiently accurate results for the goals of each unique modeling effort. This paper identifies the frequency characteristics of several different load types. It also identifies the level of load model detail required for testing typical power management systems, contingency-based load-shedding systems, frequency-based load-shedding systems, governor control systems, island/grid/unit autosynchronization systems, and exciter control systems. This paper describes how to lump loads without loss of fidelity, when an induction motor needs to be modeled as a single-cage or double-cage motor model, what sort of mechanical load model is appropriate, when we can assume zero inertia for a direct-on-line type of load, and how to verify the turbine/generator inertia, and load inertia from field tests. This paper concludes with a simple reference that engineers can use to specify the level of detail required when modeling industrial power system loads.

The structure and control strategy of a novel two-phase brushless main exciter (ME) are proposed in this paper to solve the excitation problem of the main generator (MG) when the aircraft brushless wound-rotor synchronous starter/generator start up as a motor. Two-phase symmetrical winding is adopted as the field winding of the ME and is supplied with two-phase ac by a two-phase inverter in the starting mode and dc by the traditional generator control unit in the generation mode. In order to make the field current of the MG remain constant during the start-up process, the excitation control method for the two-phase ME in the starting mode is proposed, which contains the feedback control for the two-phase field currents and speed reference control for the excitation frequency. The proposed two-phase ME and excitation control method have the advantages of capability for higher and constant field current for the MG in the starting mode and unchanged structure and control methods in the generation mode. A two-phase ME prototype, based on an original single-phase ME, is designed, manufactured, and tested. Finite-element analysis (FEA)-based simulation and experimental results verify the feasibility and advantages of the novel two-phase brushless ME and excitation control method.

In this work, the authors have studied the interaction between electromagnetic fields which are generated by lightning and overhead line in electrical power system. For this study, the authors constructed a system of equations. In which the network topology; with all its elements (linear or not) and wave exciter lightning are taken into account. This analysis is developed in time from the general equations of transmission lines with second members, with consideration of the frequency dependence of the correction terms related to the impedance of a finite conductivity of ground as well as non-linearities loads. The simulation results presented in this study demonstrate the effectiveness of this analysis for the calculation of induced voltages generated by lightning on a grid of lines.

This paper presents a novel robust adaptive AC8B exciter system against synchronous generators for ships. A PID (proportional integral derivative) control framework, which is a part of the AC8B exciter system, is simply composed of nominal and auxiliary control configurations. For selecting these proper parameter values, the former is conventionally chosen based on the experience and knowledge of experts, and the latter is optimally estimated via a neural networks optimization procedure. Additionally, we propose an online parameter learning-based auxiliary control to practically cope with deterioration of control performance owing to uncertainty in electric generator systems. Such a control mechanism ensures the robustness and adaptability of an AC8B exciter to enhance control performance in real-time implementation. We carried out simulation experiments to test the reliability of the proposed robust adaptive AC8B exciter system and prove its superiority through a comparative study in which a conventional PID control-based AC8B exciter system is similarly applied to our simulation experiments under the same simulation scenarios.

A non-contact type force actuator is necessary for studying the dynamic performance of a high-speed spindle system owing to its high-speed operating conditions. A non-contact electromagnetic exciter is designed for identifying the dynamic coefficients of journal bearings in high-speed grinding spindles. A linear force control method is developed based on PID controller. The influence of amplitude and frequency of current, misalignment and rotational speed on magnetic field and excitation force is investigated based on two-dimensional finite element analysis. The electromagnetic excitation force is measured with the auxiliary coils and calibrated by load cells. The design is validated by the experimental results. Theoretical and experimental investigations show that the proposed design can accurately generate linear excitation force with sufficiently large amplitude and higher signal to noise ratio. Moreover, the fluctuations in force amplitude are reduced to a greater extent with the designed linear control method even when the air gap changes due to the rotor vibration at high-speed conditions. Besides, it is possible to apply various types of excitations: constant, synchronous, and non-synchronous excitation forces based on the proposed linear control method. This exciter can be used as linear-force exciting and controlling system for dynamic performance study of different high-speed rotor-bearing systems.

The active health monitoring of rotordynamic systems in the presence of bearing outer race defect is considered in this paper. The shaft is assumed to be supported by conventional mechanical bearings and an active magnetic bearing (AMB) is used in the mid of the shaft location as an exciter to apply electromagnetic force to the system. We investigate a nonlinear bearing-pedestal system model with the outer race defect under the electromagnetic force. The nonlinear differential equations are integrated using the fourth-order Runge-Kutta algorithm. The simulation and experimental results show that the characteristic signal of outer race incipient defect is significantly amplified under the electromagnetic force through the AMBs, which is helpful to improve the diagnosis accuracy of rolling element bearing׳s incipient outer race defect.

Machine tools are the main driving forces of industrialization of a country. However, poor machinability because of chatter vibration results in poor surface quality, excessive noise, and reduced material removal rate. Modal testing is a useful method to investigate dynamic properties of a cutting tool system and improve material removal rate. However, at present, modal testing using impact hammer is limited by certain problems. This paper developed a non-contacting electromagnetic actuator (EMA) to determine frequency response functions (FRFs) under amplitude and speed dependencies of cutting milling tools. The geometry was designed using magnetic circuit analysis and generalized machined theory before finite element analysis was conducted using magnetostatic-ansys software. Next, EMA was used as a contacting and non-contacting exciter of a conventional milling machine to determine the FRFs and dynamic properties of milling tool with amplitude and speed dependencies including comparison with static FRFs. Subsequently, dynamic properties and FRFs are used to establish stability lobe diagram. Stability lobe diagram also shows an improvement of up to 5% of depth of cut at lower spindle speed. In conclusion, by generating force that applies to static and dynamic modal testing, an EMA can determine dynamic properties and stability lobe diagram for increasing material removal rate and production rate.

The thyristor bridge rectifier has proven to be a reliable solution regarding control of excitation equipment for synchronous generators. However, in rotating brushless exciters, the diode rectifier is the dominant topology on the shaft. In order to improve the step response of rotating exciters, one could put a thyristor bridge rectifier on the rotating part and control the firing angle remotely from a stationary controller. This paper compares different multiphase configurations of permanent magnet synchronous machines as a rotating exciter and discusses the possibility to reduce the torque ripple by selecting the appropriate rectification topology. The paper also explains the implications of the self and mutual inductances of the armature windings for the performance of the exciter.

Conventional electro-hydraulic excitation is usually controlled by a servo valve employing a sliding spool type construction. However, the comparatively slow response of the servo valve will greatly limit the system's high-frequency performance. Therefore, a rotary valve with the rotary motion of the spool as a new excitation mechanism is proposed to obtain the desired excitation, especially a high-frequency excitation wave for fatigue. An electro-hydraulic exciter using a combination of a three-way two-dimensional rotary valve (2D rotary valve) and an unequal area piston is taken as an example. Analysis of the vibration output to a typical wave input yields an analytic solution of the vibration waveform excited by this electro-hydraulic system. The mathematical formulation of the harmonics is also derived. Additionally, an electro-hydraulic excitation test-bed is built to acquire an experimental excitation wave. Consequently, the analysis of the excitation waveform in an approximate analytical and experimental method is used to verify access to high-frequency excitation, even resonance excitation.

The important part of the validation and certification of the new product are vibration and shock testing of mechanical, electrical and electronic equipment components that are mounted on rail vehicles. The hydraulic shaker is possible to use as the vibration and shock exciter to simulate the effect of the environment to the specimen. It is necessary to fulfil the prescribe condition of the level of mechanical vibration and the acceleration peak of the shock test signals. The specific hydraulic motor produced by INOVA is designed for the specific vibration test and the aim is to use it also for the shock tests. The control algorithm uses two iteration methods in time and frequency domain and their use depends on test prescription.

When a shaker (or exciter) connects to a structure under test (SUT), the dynamic characteristics of the excitation system (shaker, stinger, and transducers) becomes coupled with those of the SUT. These couplings contaminate recorded measurements, especially while exciting light/flexible SUTs. The aim of this work is to consider interactions between excitation system and the SUT and introduce a new analytical model for prediction and hence reducing this systematic error. With the aid of this model, changes in dynamic stiffness of the SUT are estimated based on stiffness of the excitation system. The effects of excitation system location and stiffness are shown in modal testing on a free–free beam. Furthermore, influence of force transducer location is studied in the excitation system setup. The proposed method is successfully used for identification and prediction of excitation system effects on dynamic characteristics of the beam.

In this paper the effect of heat on the performance of novel energy harvester (NEH) by using PZT-5H circular transducers was mentioned. PZT-5H circular transducers were heated at three different temperatures such as 20 0 C, 60 0 C and 100 0 C and tested on 20 g exciter under sinusoidal support excitation by using NEH. The observations were made on three parameters: temperature effect on impedance, temperature effect on resonant frequencies and temperature effect on the output voltage. At 20 0 C, the output voltage is 23 V and at 100 0 C the output voltage is 18 V is recorded. The observation is that the temperature effects the performance of PZT-5H circular transducers.

The paper is focused on the design and development of the system simulating nonlinear attachment of the aileron actuation on the aeroelastic demonstrator. The system is based on the concept of the digitally controlled additional stiffness, activated by the real time control law system, controlling the required ratio of the force and deformation. The solution is based on the electromagnetic exciter. The nonlinear force is simulated by means of the system of the exciter and the deformation sensor. The active control system is independent of the excitation system. It adds the force ensuring the required characteristics and it allows to simulate the additional stiffness, damping or mass. Doing this, it is possible to adjust the selected vibration mode by controlling the force and obtain the required nonlinear characteristics. In the second order, there is also a constant influence of the exciter mass, stiffness and damping. The simulation of the linear, quadratic and cubic additional stiffness were verified.

This paper deals with an active structural acoustic control approach to reduce the transmission of tonal noise in aircraft cabins. The focus is on the practical implementation of the virtual mechanical impedances method by using sensoriactuators instead of conventional control units composed of separate sensors and actuators. The experimental setup includes two sensoriactuators developed from the electrodynamic inertial exciter and distributed over an aircraft trim panel which is subject to a time-harmonic diffuse sound field. The target mechanical impedances are first defined by solving a linear optimization problem from sound power measurements before being applied to the test panel using a complex envelope controller. Measured data are compared to results obtained with sensor–actuator pairs consisting of an accelerometer and an inertial exciter, particularly as regards sound power reduction. It is shown that the two types of control unit provide similar performance, and that here virtual impedance control stands apart from conventional active damping. In particular, it is clear from this study that extra vibrational energy must be provided by the actuators for optimal sound power reduction, mainly due to the high structural damping in the aircraft trim panel. Concluding remarks on the benefits of using these electrodynamic sensoriactuators to control tonal disturbances are also provided.

The aerospace and military communities have performed vibration tests for decades using a single axis or single degree of freedom (SDOF) approach. In recent years, military standards have recognized a multiple exciter or multiple degree of freedom (MDOF) approach for conducting vibration testing. This primer on MDOF vibration testing serves to introduce the topic to the IMAC community and fits with IMAC-XXXVI’s theme: Engineering Extremes.

The use of the vehicle-bridge interaction (VBI) data for structural health monitoring has received considerable interest in the last decade. Compared with the traditional bridge health monitoring, the VBI based approach allows the target bridges to be monitored or assessed under operating conditions. The VBI system has time-variant features and the vehicle can serve as a moving exciter and a mobile sensor in the system. Many bridge damage identification techniques based on VBI have been developed, and they could be divided into three categories, namely, technique based on the bridge responses, technique based on the vehicle responses and technique based on both the vehicle and bridge responses. This paper presents a review on the structural health monitoring based on VBI and the challenges for its general implementation in practice.

In this paper, a model is developed to incorporate the magnetic hysteresis effects into a brushless exciter model. The developed model reconstructs the magnetization flux linkage current loops using the Energetic hysteresis model. The model requires measurements from the armature and field terminals of the brushless exciter at standstill, and the model can be applied for detailed analysis of brushless excited synchronous generators. The developed model is also verified experimentally through measurements on a brushless excited synchronous generator.

This study discusses the use of time-delayed remote signals available through phasor measuring units (PMUs) for low-order controller design in order to stabilise the power oscillations in the range of 0.3–0.42 Hz between two areas. In the proposed approach, first synchronisation measures are determined among the group of generators located in two areas. Then, an index that characterises the joint observability and controllability property in terms of Hankel singular values is defined as a criterion to preselect the remote feedback signal. Following this, a low-order controller design based on minimisation of H ∞ norm is considered. The measurement redundancy is taken into account in controller design using rotor angle, power flow or speed deviation as feedback signal from one of the generators. Additionally, if some specific PMU fails to provide measurements from a chosen generator, then controller effectiveness is guaranteed using signal from other generator in the same area. The performance of controller is verified considering single-step and multi-step disturbances applied to the reference voltage of exciter system. The comparison with design functions such as H 2 norm, complex stability radius and spectral abscissa are also presented. The analytical results confirm using H ∞ design algorithm provides better dynamic performance.

A reduced model approach to decrease computational complexity in power system transient stability simulation is presented. This study investigates conditions that make fast modes active or inactive using practical power system examples. Modes in the original system where fast dynamics do not appear can be neglected, allowing simulation steps to be increased without numerical stability issues. During a transient simulation, the proposed method switches dynamically between the original exciter model and the reduced one, depending on the switching criterion presented. A high level of accuracy is achieved and computational efficiency is increased. Case studies with the Western Electricity Coordinating Council system are provided to validate the performance of the proposed method.

Explicit numerical integration methods for power system transient stability simulation require very small time steps to avoid numerical instability. The EXST1 exciter model is a primary source of fast dynamics in power system transients. In case of the EXST1, the required small integration time step for entire system simulation increases the computational demands in terms of running time and storage. This paper presents a practical exciter model reduction approach which allows the increase of the required step size and thus the method can decrease the computational demands. The fast dynamics in the original EXST1 are eliminated in the reduced exciter model. The use of a larger time step improves the computational efficiency. This paper describes the way to eliminate the fast dynamics from the original exciter model based on linear system theory. In order to validate the performance of the proposed method, case studies with the GSO-37 bus system are provided. Comparisons between the original and reduced models are made in simulation accuracy and critical clearing time.