Brushless Synchronous Generator Research Articles

Influence of Temperature on Brushless Synchronous Machine Field Winding Interturn Fault Severity Estimation

There are numerous methods for detecting interturn faults (ITFs) in the field winding of synchronous machines (SMs). One effective approach is based on comparing theoretical and measured excitation currents. This method is unaffected by rotor temperature in static excitation SMs. However, this paper investigates the influence of rotor temperature in brushless synchronous machines (BSMs), where rotor temperature significantly impacts the exciter excitation current. Extensive experimental tests were conducted on a special BSM with measurable rotor temperature. Given the challenges of measuring rotor temperature in industrial machines, this paper explores the feasibility of using stator temperature in the exciter field current estimation model. The theoretical exciter field current is calculated using a deep neural network (DNN), which incorporates electrical brushless synchronous generator output values and stator temperature, and it is subsequently compared with the measured exciter field current. This method achieves an error rate below 0.5% under healthy conditions, demonstrating its potential for simple implementation in industrial BSMs for ITF detection.

An efficient integrated model for diesel‐engine three stage brushless synchronous generator

AbstractBrushless power generation sets are a technology of choice for on‐board power generation in aerospace and marine applications, emergency and backup power systems, etc. Efficient modelling of these systems is necessary for various purposes such as design, analysis, control and specially condition monitoring. An accurate and efficient model of a diesel‐engine generator‐rectifier system consisting of a three stage brushless synchronous generator is presented. The constant parameter voltage‐behind‐reactance model of the pilot exciter (PE), main exciter (ME) and main generator are derived and integrated to form a unified model suitable for efficient simulation of a diesel‐engine brushless generation system. Simulation studies are carried out in MATLAB using PLECS toolbox and the results are compared to experimental results to verify the performance of the proposed integrated model.

Application of Acoustic Signals for Rectifier Fault Detection in Brushless Synchronous Generator

One of the most important issues that power companies face when trying to reduce time and cost maintenance is condition monitoring. In electricity market worldwide, a significant amount of electrical energy is produced by synchronous machines. One type of these machines is brushless synchronous generators in which the rectifier bridge is mounted on rotating shafts. Since bridge terminals are not accessible in this type of generators, it is difficult to detect the possible faults on the rectifier bridge. Therefore, in this paper, a method is proposed to facilitate the rectifier fault detection. The proposed method is then evaluated by applying two conventional kinds of faults on rectifier bridges including one diode open-circuit and two diode open-circuit (one phase open-circuit of the armature winding in the auxiliary generator in experimental set). To extract suitable features for fault detection, the wavelet transform has been used on recorded audio signals. For classifying faulty and healthy states, K-Nearest Neighbours (KNN) supervised classification method was used. The results show a good accuracy of the proposed method.

DIODE EXCITERS OF A BRUSHLESS MEDIUM POWER SYNCHRONOUS GENERATOR

The aim of the work is a comparative analysis of the parameters of the diode exciter of a brushless synchronous generator of medium power on the number of pole pairs of an auxiliary electric machine, the development of recommendations for choosing the number of pole pairs of an auxiliary electric machine and the design of the exciter.
 An improvement of the automated method of electromagnetic calculation of the exciter of a brushless synchronous machine has been carried out. The diode exciters of a brushless synchronous generator with a power of 250 kW with the number of pole pairs p = 2 based on a three-phase bridge rectifier and an auxiliary electric machine of a synchronous type with different numbers of pole pairs are compared. At the first stage, a preliminary electromagnetic calculation of the auxiliary electric machine is performed, taking into account the initial value of the relative magnitude of the resulting electromotive force, the allowable values ​​of inductions in all sections of the magnetic circuit in in forced mode, the length of the magnetic circuit and the rotor winding support are determined. According to the results of the calculation of the rectifier model in the quasi-steel mode of operation, the relative value of the resulting electromotive force of the auxiliary electric machine is specified. 
 At the first stage, a preliminary electromagnetic calculation of the auxiliary electric machine is performed, taking into account the initial value of the relative magnitude of the resulting electromotive force, the allowable values ​​of inductions in all sections of the magnetic circuit in in forced mode, the length of the magnetic circuit and the rotor winding support are determined. According to the results of the calculation of the rectifier model in the quasi-steel mode of operation, the relative value of the resulting electromotive force of the auxiliary electric machine is specified pB = 4.

Synchronous Homopolar Generator without Permanent Magnets for Railway Passenger Cars

The article presents the optimal design of a 35 kW brushless synchronous homopolar generator without permanent magnets for railway passenger cars. The excitation winding of the generator is located on the stator, and the toothed rotor has no windings. The generator characteristics are optimized considering the required constant power speed range. A single-objective Nelder–Mead algorithm and 2D Finite Element Analysis were used for the optimization. As a result of the optimization, power losses are significantly reduced over the entire operating range of the generator rotational speed, the current capacity of the solid-state rectifier, and the torque ripple. A comparison of the calculated characteristics of the generator under consideration with the characteristics of a commercially available undercar generator shows that the active volume is reduced by a factor of 2.1, and the losses are significantly reduced over the entire operating speed range.

BRUSHLESS EXCITATION SYSTEM ELECTROMAGNETIC DESIGN AND ANALYSES

The brushless synchronous generator (SG) excitation system consists of a main exciter, a permanent magnet generator (PMG) of consequent rotor poles type, and an automatic voltage regulator (AVR). Both exciter machines have been properly designed and analysed. The machines performances are obtained by time stepping finite-element method (FEM) coupled with the external electrical circuit. An experimental machine is built and the measured results are given.

Minimization of DC-Link Capacitance for a DC-Link-Based Variable Speed Constant Frequency Aircraft Power System

DC-link-based variable speed constant frequency (VSCF) ac power generating system is being considered as one of the popular power architectures in the new generation aircraft to provide backup power to the 115 V, 400 Hz aircraft loads. These systems directly convert the variable frequency output of the generator to the fixed frequency of 400 Hz using a voltage source inverter. These inverters use dc-link capacitors that are heavy and space consuming. In aircraft, the weight requirement is very critical; hence, minimizing the dc-link capacitance is one of the major research challenges to achieve high power density in the VSCF power converter. In this article, novel control strategies to minimize the dc-link capacitance of the ac–dc–ac VSCF power converter are presented. The proposed control strategies enable to achieve 95% reduction in dc-link capacitance value when compared with the conventional control strategy, while the control is robust enough to meet MIL-STD-704F transient specification at the inverter output. The proposed strategies are validated through controller hardware-in-loop testing of the VSCF system based on an 80 kVA brushless synchronous generator and a four-leg inverter. The transient and steady-state operation of the VSCF system with a 95% reduction in dc-link capacitance has been verified for rated power operation.

Design Method for Variable Frequency Brushless Synchronous Generators

Brushless synchronous generators, which have the structure of three-stage generators to realize brushless excitation, are the most commonly used aero-generators. With the development of more electric aircraft technology, the output frequency of aero-generators is changing from constant to variable, and the characteristics of generators are also changed. To make sure that the generators can be adapted to the variable frequency operation, this paper analyzes the effects of different operating conditions on generator performance and proposes corresponding design methods. The design and verification of the electromagnetic field, fluid field, temperature field and stress field are carried out for the variable frequency generator. A prototype generator is manufactured according to the design results. An experimental platform is set up to test the performances of the designed generator. The final experimental results show that the generator can work well in variable frequency generation systems, which proves the design method proposed in this paper is effective and feasible.

Бесконтактный генератор с регулируемым возбуждением

Wind turbines are further developed toward improving their reliability and efficiency, and reducing maintenance costs during long-term operation. For this purpose, synchronous generators with excitation from permanent magnets are used, the parameters of which determine in many respects the efficiency and dimensions of the power plant as a whole. The article proposes a new design of a brushless synchronous generator with excitation longitudinal with respect to the rotor rotation axis. The generator features a simple design of its rotor poles and double frequency of the secondary winding voltage. The possibility of manufacturing the stator housing from cheap plastic or similar non-magnetic materials is noted, due to which a reduction in the generator mass and cost can be achieved; such generator can find use mainly in small and medium capacity power plants. To close the rotor excitation magnetic flux, longitudinal magnetic cores with coils on them are installed in the slots of the non-magnetic stator housing. This makes it possible to improve heat removal from the secondary winding and simplify the assembly. Smooth adjustment of the output voltage in a wide range of rotation speeds is possible. The results of modeling the magnetic field in the air gap between the stator and rotor and the output voltage waveform for the basic magnetic system configuration are presented.

Adaptive fuzzy excitation regulator of a brushless synchronous generator

Adaptive fuzzy excitation regulator of a brushless synchronous generator

A Novel Fuzzy PI Control Method for Variable Frequency Brushless Synchronous Generators

With the application of more electric aircraft (MEA) technology, variable frequencies and high power ratings become import features of aero-generators. The brushless synchronous generator, which has a three-stage structure, is the most commonly used type of aero-generator. Due to the variation of operating conditions, the implementation of generator controllers becomes more and more difficult. In this paper, a state space model of a generator is derived and the influence of different operating conditions on the frequency response characteristics of the generator is revealed. Based on a fuzzy PI controller, an additional fuzzy logic controller is applied to modify the PI parameters of the voltage loop by introducing the generator speed to cope with the speed variation. Finally, the results of the simulations and experiments demonstrate that the dual fuzzy PI controller can improve both the steady-state and dynamic performance of the brushless synchronous generator, verifying the previous theoretical study.

Comparative Study on Performance of Aeronautical ISG Based on Brushless Synchronous Generator and PMSG

In this paper, the simulation analysis and research on the starting and generating system based on two-stage brushless synchronous motor and permanent magnet synchronous motor are respectively carried out, and the brushless synchronous motor AC/DC mixed excitation scheme is proposed. The starting operation adopts vector control, and the output voltage precision is improved by adjusting the excitation voltage of the exciter. A permanent magnet synchronous motor starting and generating system is constructed, and the control of starting and generating is realized by using vector control based on SVPWM, the results show that the permanent magnet synchronous motor has fast starting speed, good dynamic and static performance, high power supply quality and simple hardware composition, which reduces the complexity of the control system and is convenient for engineering implementation.

Emergency Brushless Synchronous Generator Having Rotating Exciter Status Monitoring and Protection Functions

This paper presents an emergency brushless synchronous generator having rotating exciter status monitoring and protection functions. For monitoring the rotating exciter status, a wireless rotor status detector and a digital AVR(Automatic Voltage Regulator), which has a wireless communication capability, are proposed. The proposed rotor status detector detects temperatures of exciter armature and main field windings and input voltage and current of the main field. Therefore, it is possible to protect the generator from the over-temperature of windings and detect the exciter bridge diode fault. Furthermore, the proposed digital AVR has rotor status monitoring and protection function, and remote generator tuning, wireless group parallel operation function. So the operator can efficiently operate the generator using a smartphone from a remote area.

Diagnosis of brushless synchronous generator using numerical modeling

PurposeOn-time fault diagnosis in electrical machines is a critical issue, as it can prevent the development of fault and also reduce the repairing time and cost. In brushless synchronous generators, the significance of the fault diagnosis is even more because they are widely used to generate electrical power all around the world. Therefore, this study aims to propose a fault detection approach for the brushless synchronous generator. In this approach, a novel extension of Relief feature selection method is developed.Design/methodology/approachIn this paper, by taking the advantages of the finite element method (FEM), a brushless synchronous machine is modeled to evaluate the machine performance under two conditions. These conditions include the normal condition of the machine and one diode open-circuit of the rotating rectifier. Therefore, the harmonic behavior of the terminal voltage of the machine is obtained under these situations. Then, the harmonic components are ranked by using the extension of Relief to extract the most appropriate components for fault detection. Therefore, a fault detection approach is proposed based on the ranked harmonic components and support vector machine classifier.FindingsThe proposed diagnosis approach is verified by using an experimental test. Results show that by this approach open-circuit fault on the diode rectifier can effectively be detected by the accuracy of 98.5% and by using five harmonic components of the terminal voltage [1].Originality/valueIn this paper, a novel feature selection method is proposed to select the most effective FFT components based on an extension of Relief method, and besides, FEM modeling of a brushless synchronous generator for normal and one diode open-circuit fault.

Winding Fault Diagnosis and Failure Prognosis Technique for Brushless Synchronous Generator

Winding fault diagnosis and failure prognosis technique has been developed based on d-q model of brushless synchronous generator (BLSG) considering actual winding insulation degradation curve of machine in inter-turn fault, damper bar and field currents for various severities of inter-turn winding faults have been estimated using extended Kalman filter. For validation of damper bar currents, 2 D transient electromagnetic analyses using finite element method have been done, and 2nd harmonic component of damper bar currents for various severities of inter-turn fault in stator windings have been computed by Fourier transformation. The winding insulation degradation curve of machine has been determined by accelerated life test, and used for estimation of remaining useful life of machine under inter-turn fault, assuming a pre-defined failure threshold. Actual and predicted life of the BLSG has been compared. Wireless sensors using rotor telemetry system have been mounted on the rotor of BLSG for experimental validation of field currents under winding faults. The 2nd harmonic of damper bar currents increase with increase in severities of winding faults and do not get affected by diode failures in rotating rectifier, hence this can be used as a robust fault indicator for diagnosis and prognosis of inter-turn winding fault in BLSG.

Power loss and efficiency analysis of an onboard three-level brushless synchronous generator

ABSTRACT This paper develops a mathematic model to calculate the power losses and efficiency for an onboard three-level brushless synchronous generator (TLBLSG) which consists of pilot exciter (PE), main exciter (ME), and main generator (MG). A back-iteration algorithm which combines an analytical model of the MG stator loading with a three-phase diode bridge rectifier (TPDBR) and a capacitor, an equivalent circuit model of the MG, and a model of steady-state excitation current based on the open circuit characteristic (OCC) is employed to determine the electrical parameters in the MG. Besides, both ME rotor and PE stator currents are calculated by the model of induced electromotive force loading with a TPDBR and an inductance. All the obtained electrical parameters can reflect the influence of rotating speed and load change as well as the saturation effect. Finally, changing laws of the electrical parameters and power losses as a function of speed and load are simulated and discussed in detail. Moreover, efficiencies under different speeds and loads are analysed. The TLBLSG is suggested to be operated in a relatively high-speed range (from 15,000 to 25,000 r/min) and a relatively large load (from 25 to 65 kW) for a high efficiency.

Non-Salient Brushless Synchronous Generator Main Exciter Design for More Electric Aircraft

This paper presents a prototype of high speed brushless synchronous generators (BSG) design for the application in autonomous electric power generation systems (e.g., airplane power grid). Commonly used salient pole field of the main generator part of BSG was replaced with a prototype non-salient pole field. The main objective of the research is an investigation into the advantages and disadvantages of a cylindrical field of the main generator part of BSG over the original salient pole field. The design process of the prototype generator is presented with a focus on the electromagnetic and mechanical finite element method (FEM) analysis. The measurements of prototype and commercial BSG were conducted for the nominal speed of 8 krpm. The advantages and disadvantages of the proposed solution were established based on measurements in load and no-load conditions.

Performance and Analysis of a New Brushless Synchronous Generator for DC Microgrid Application

DC grid is gaining popularity as different renewable energy sources and energy storage elements used to form the microgrid are dc in nature. Moreover, HVdc systems have been found to be advantageous for off-shore wind farms. For such systems located in remote places, maintenance becomes a key issue, which makes the use of brushless generator preferable. Very recently, a new synchronous generator with embedded brushless synchronous exciter has been reported. This work explores the performance of such generators for dc microgrid application. A simple diode rectifier is used to interface the generator to the dc grid. Such uncontrolled rectifier will cause current quality issues. A passive tuned filter can help in mitigating this issue and also assist in improving the voltage regulation by providing reactive power support. A method to select the right filter parameters has been proposed. Simulation results obtained from MATLAB/Simulink and experimental results from a fabricated laboratory prototype have been presented. Both simulation and experimental results reveal the effectiveness of the proposed system.

Neighbors Class Solidarity Feature Selection for Fault Diagnosis of Brushless Generator Using Thermal Imaging

This article aims to propose a thermography-based fault detection approach for a brushless synchronous generator. In this approach, the energy of 2-D wavelet coefficients is utilized to extract features from thermal images. In order to select the appropriate wavelet basis function and decomposition level (DL), a novel filter feature selection called neighbors class solidarity (NCS) is propounded. To this purpose, the energy of the approximation coefficients is obtained for 65 wavelet basis functions and 12 DLs. Subsequently, the best feature is selected by using NCS. The selected feature is then applied to $k$ -nearest neighbors and support vector machine in order to classify the images into three operational states. These states include healthy, one diode open-circuit fault of the diode rectifier, and one open-phase fault of the exciter armature, while the tests are conducted under three different load conditions for each state. Results imply the efficiency of the proposed approach for the fault diagnosis in the brushless synchronous generator with an accuracy of 95.1%. To evaluate the performance of the NCS, it is compared with other conventional filter feature selection methods, and also for different test analysis.

A Wrapper-based Feature Selection Approach for Accurate Fault Detection of Rotating Diode Rectifiers in Brushless Synchronous Generators

Fast and accurate fault detection is a vital issue for all engineering systems, especially for those which generate power for sensitive applications. To achieve rapid and accurate fault detection, an appropriate signal must be measured and the best features of that signal should be extracted. In this paper, an approach is proposed to detect the healthy and faulty states of a rotating diode rectifier in a brushless synchronous generator by using three-phase terminal voltage. There is not any direct access to the rectifier, and therefore, fault detection must be performed using signals from the machine itself. In order to extract the correct voltage signal, fast Fourier analysis is performed on the signal, and to select the best frequency to reduce redundancy and increase classification accuracy, a wrapper-based feature selection approach is utilised. In this approach, the best frequency is selected from among the frequencies generated according to the accuracy of the classifier, a Support Vector Machine (SVM). The other frequencies are then added one by one according to their accuracy in each step, and the best subset, that is, the one with the best accuracy for the classifier, is selected. The proposed approach is then evaluated using experimental data.