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A dual-excited synchronous generator (DESG) with two field windings on the rotor has better dynamic characteristics and high stability. However, the realization of the function needs a reasonable excitation control strategy. In this article, a power tracking excitation control (PTEC) is proposed to improve the operating performances of the DESG. The dynamic processes of a 300-MW DESG with the PTEC are calculated after the disturbance of the torque and reactive power by the time-stepping finite element model, and the results are superior to those adopting the traditional dual-channel excitation control. To further improve the dynamic characteristic of the DESG, the sensitivities of the control parameters of the PTEC to the dynamic characteristic indices are studied. The fuzzy control rules are built based on the sensitivity analysis results and the control parameters are optimized by the fuzzy control method. It revealed the variation laws of the optimized control parameters along with the active and reactive power deviations and their variable rates. The results show that the DESG adopting the optimized control parameters has better dynamic characteristics. The study can provide the theoretic basis for enhancing the system damping effect and suppressing the system oscillation. [ABSTRACT FROM AUTHOR]

The rotor temperature rise of high voltage line-start solid rotor permanent magnet synchronous motors (HVLSSR-PMSMs) may be too high while operating, which properly causes thermal demagnetization for permanent magnets. Therefore, it is necessary to perform the thermal investigation on HVLSSR-PMSM. In this article, a 315-kW, 6-kV HVLSSR-PMSM with the air-cooled hybrid ventilation system is studied in the view of thermal phase. The losses, obtained from the electromagnetic analyses, are applied to the thermal investigation as the distributed heat sources. Whereas, both the mathematical and the geometrical models are proposed for the three-dimensional (3-D) fluid-thermal coupled investigation, from which the fluid velocity and the temperature in motor different components are determined. Whereas, with the hybrid ventilation system, temperatures in motor different components reduce, obviously comparing with those in motor with the original cooling system. The experimental investigations are performed on prototypes in both cases, which verify the calculation results and approve the effectiveness of the proposed hybrid air cooling system as well. [ABSTRACT FROM AUTHOR]

Extension lengths of the stator and rotor end windings will obviously affect the electromagnetic field, fluid flow, and temperature of end components in the end zone of large water-hydrogen-hydrogen cooled turbine generator. In this paper, a 330 MW water-hydrogen-hydrogen cooled turbine generator is analyzed. Flow network of this turbine generator is established. The fluid velocity and the pressure (boundary conditions) are obtained at the different positions of this turbine generator after solving the equations of flow network. Three-dimensional transient electromagnetic field is calculated in the turbine generator end zone. The leakage magnetic field and the losses (heat source) of end components are determined in the turbine generator end zone under the different lengths of stator and rotor end winding extension. Based on these results, three-dimensional fluid-thermal coupled model is given in the end zone. The distribution of complex fluid velocity in the turbine generator end zone is determined. The temperature distribution of the stator end winding, clamp plate, electric screen, and finger plate is studied under the different lengths of stator and rotor end winding extension. The calculated temperature results agree well with the measured values. [ABSTRACT FROM AUTHOR]

The structure of a permanent magnet synchronous motor (PMSM), more precisely, its shape and dimension of the stator slot can change the magnetic field distribution of the stator tooth and the yoke. In addition, it also affects the magnetic field distribution in the air‐gap and the electrical loss in the rotor. As a result, there is an effect on the motor's internal temperature distribution. This study aims at investigating the influence of stator slot dimension on the performance of the motor. To this extent, a field‐circuit coupled model combining the vector control strategy with motor finite element model is proposed. Based on this model, the impact of using various opening widths of semi‐closed slot and the dimension of the closed slot on both magnetic field distribution and loss in the PMSM is studied in detail. Furthermore, by considering the calculated loss as a heat source, the temperature variation of the stator core, winding, magnetic bridge and permanent magnet of the motor for different scenarios of slot dimensions can be obtained by using a three‐dimensional temperature field model at steady‐state. An experimental platform is established to validate the model this provides a theoretical support for the analysis of the results. [ABSTRACT FROM AUTHOR]

Axial–radial flux type permanent magnet synchronous machine can adjust air gap flux, which provides a new strategy for flux regulation of a permanent magnet motor. In this article, the structure of the ferromagnetic bridge is optimized by analyzing the magnetic circuit structure of Numerical anlysis of an axial-radial flux type fully superconducting synchronous motor (ARFTFSSM). The three-dimensional finite-element model of the motor is established by using the finite-element method, and the changes of air gap flux density and back electromotive force are compared through the finite-element prediction. The results show that the optimized ferromagnetic bridge has better magnetic regulation performance. On this basis, the eddy current distribution and eddy current loss of two kinds of ferromagnetic bridge structures are further compared and analyzed. Finally, the experimental results verify the accuracy of the calculation, and the research results can provide a reference for the further study of hybrid excitation motor. [ABSTRACT FROM AUTHOR]

To investigate the influence of different electric shield materials on the temperature distribution in the turbogenerator end region, a 330-MW water–hydrogen–hydrogen-cooled turbogenerator is considered in this paper. Mathematical and physical models of the three-dimensional (3-D) transient electromagnetic field in the turbogenerator end region are established. The magnetic density distribution and the losses of end parts are obtained with different electric shield materials. The loss values obtained from the 3-D transient electromagnetic field calculations with different electric shield materials are applied to the end parts as heat sources. Pressure and fluid velocity values from flow network calculations are applied to the end region as boundary conditions for the fluid and thermal coupling analysis. In addition, a 3-D fluid and thermal coupling model of the turbogenerator end region is established. The distributions of the surface heat transfer coefficient on the inner and outer surfaces of the electric shield are determined with different electric shield materials. Temperature distributions of the stator-end copper winding, finger plate, clamping plate, and electric shield in the turbogenerator end region are investigated with different electric shield materials. The calculated temperature results for the electric shield are compared with measured values, and the calculated results agree well with the measured values. [ABSTRACT FROM AUTHOR]

Flywheel energy storage system (FESS) has been widely used in many fields, benefiting from the characteristics of fast charging, high energy storage density, and clean energy. Uncontrollable discharging system can be used in some special occasions which doesn't have strict requirements on the power quality, such as electric heaters, emergency power supplies, etc. Taking a charging and discharging (C&D) system of 200 kW 15000 rpm high-speed Permanent Magnet Synchronous Motor/Generator (PMSM/G) used for FESS as an example, field-circuit coupling calculation model of PMSM/G during the process of controllable charging and uncontrollable discharging is established. And then the relationships between speed and current-voltage during charging process is calculated. A variable load calculation method based on transient electromagnetic field during the process of uncontrollable discharging is presented, and the eddy current field and transient temperature field of rotor sleeve and permanent magnets during the process of C&D under different loads are also calculated. The output characteristic curves of FESS under condition of constant loads during the process of uncontrollable discharging is drawn. The conjugate analysis method of rotor multi-physical fields is proposed to study the relationships between rotor sleeve stress and eddy current distribution, and the optimized sleeve thickness for high-speed PMSM/G is also presented. Also, a solution is presented to solve the temperature and sleeve fracture problems caused by eddy current under high-speed operation. This contents of the paper can provide references for efficient and reliable design of PMSM/G under extreme conditions used for FESS. [ABSTRACT FROM AUTHOR]

• The incident angle of hydrogen considering the rotor rotation is concerned. • The ventilation test and temperature test of the steam generator are made. • The fluid velocity vector field are investigated. • The pressure loss in the multi-direction ventilation duct are studied. • The temperature field of the rotor is focused. During the operation of a large-scale turbine-generator, hydrogen enters the ventilation ducts of the rotor with turbulent state, so that the inlet direction of hydrogen is difficult to solve under the influence of rotor rotation. The cooling effect of the rotor coil can be effected by the mainstream of hydrogen entering the ventilation ducts. With regard to this, it takes an 1100 MW turbine-generator with axial ventilation system, as a test generator, global fluid network equation is carried out to calculate the pressure field and velocity field of hydrogen in the rotor ventilation ducts. Based on the calculations, the fluid and heat transfer nonlinear equation for the rotor is established and calculated via finite volume method (FVM). First, the hydrogen flow law in the complex ventilation duct is investigated and the pressure losses of hydrogen in the corners from the rotor radial inlet area to the axial flow area and then into the radial outlet area are analyzed. Second, the rotor temperature fields are highlighted and investigated in the condition of incident angle α = 0°, 15°, 30°, 45°. The incident angle α = 0° indicates vertical state between hydrogen flow direction and the rotor vent inlet. Simultaneously, the calculations of the average temperature in the rotor coils are compared with the experimental results to verify the accuracy of the calculation method. Additionally, the temperature distribution of rotor varying with the circumferential direction is investigated, which can provide theoretical basis for the larger scale turbine-generator. [ABSTRACT FROM AUTHOR]

For surface mounted permanent magnet synchronous motor (PMSM), due to the large rotor rotational centrifugal forces, a sleeve is often used to prevent damage to rotor permanent magnets. However, eddy current losses appearing in the sleeve can increase the temperature of surface mounted PMSM. If the rotor heat dissipation condition is poor, high temperature can influence the surface mounted PMSM performance and even result in thermal demagnetisation of the permanent magnets. Thus, a sleeve scheme designed with low eddy current loss is very necessary. In this study, taking a 12.5 kW, 2000 rpm PMSM with 0.2 mm thickness stainless steel sleeve as an example, first, the influences of sleeve thickness on the eddy current loss and temperature field are analysed. Then, sleeve various composition structures of carbon fibre and stainless steel are presented, and the influences of different composition percentages on the eddy current losses and temperature field are analysed in detail, which shows the effectiveness in reducing the eddy current losses and temperature in the rotor. The obtained conclusions can provide useful reference for the design and research of surface mounted PMSM. [ABSTRACT FROM AUTHOR]

This paper addresses the effect of rotor structure on the magnetic adjusting performance of an axial-radial permanent magnetic machine via the comparative performance investigation on the axial-radial flux type permanent magnet machines with three different structures. By using the three-dimensional time stepping finite-element method, the distributions of the air-gap flux density are obtained when the machine operates with different axial magnetomotive force, and the key factor that affects the magnetic adjusting ability is determined. The variation of the magnetic field is investigated, and the back electromotive forces of the three machines with different structures are also studied. Meanwhile, the eddy current distribution and the eddy current loss in machines with different structures during load operation are analyzed. The theoretical claims are verified by both numerical simulations and experimental tests. [ABSTRACT FROM PUBLISHER]

The premium induction motor has received worldwide attention in recent years due to its high efficiency. However, the high efficiency benefits from the high cost. In the paper, a multiphysical field collaborative optimization method of the premium induction motor based on the genetic algorithm (GA) is presented to improve the utilization of the materials and reduce the cost. First, the cost and efficiency are taken as bi-objective; the magnetic circuit optimization based on GA is established to get the initial electromagnetic scheme. Then, the parameters of the premium induction motor are automatically transferred to a 2-D transient electromagnetic field calculation model so that the operation performances of the premium motor can be determined. The results will be sent to the magnetic circuit optimization to compare with the optimization objectives. The electromagnetic scheme will adjust until the errors between the transient operation performances and optimization objectives are within the convergence errors. Based on the results above, the transient results will be transferred to the 2-D temperature field calculation model to determine the thermal distributions of the premium induction motor. The structures of the premium induction motor will also adjust until the thermal distributions meet the requirements. The presented multiphysical field collaborative optimization method is applied to optimize several premium motors, and the accuracy is validated by the experimental data. [ABSTRACT FROM PUBLISHER]

Synchronizing out of phase may sometimes occur to a turbine generator due to the misoperation or failure of a synchronizing controller. There could be a large impulse current in stator windings during out of phase synchronizing. The impulse current could seriously damage the windings insulation, and the magnetic flux density might be easily supersaturated at the rotor pole surface, leading to stronger stress on the rotor tooth and damage the turbine generator. Aiming at studying the electromagnetic field when synchronizing out of phase occurs, a mathematical model of the transient electromagnetic field with field-circuit-grid coupled is established by taking a 150 MW air-cooled turbine generator for consideration. Impulse current in stator winding and supersaturation at the rotor pole surface are calculated respectively in different angles between the vector of the turbine generator electromotive force and voltage vector of power grid. According to the largest impulse current in stator windings at the 180° out-of-phase synchronization, the influence on the magnetic field distribution and saturation at the rotor pole surface of turbine generator stator resistance and the end region leakage inductances that vary in a certain range is studied. The results could provide theoretical basis for researching of electromagnetic field at out-of-phase synchronization of large turbine generator in the end zone. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel Continuous Quantum Immune Clonal Optimization algorithm for thermal optimization on a 117 kW high-speed permanent-magnet generator (HSPMG). The proposed algorithm mixes the Quantum-Computation into the Immune-Cloning-Algorithm and causes better population diversity, higher global searching ability, and faster convergence which is approved by simulation results. Then, the improved algorithm is applied to seek an optimized slot groove and improve HSPMG thermal performance, where the 3-D fluid-thermal coupling analyses are processed with a multiobjective optimal group composed of the highest temperature and temperature difference. Both the proposed algorithm and the obtained conclusions are of significances in the design and optimization of the cooling system in electric machines. [ABSTRACT FROM AUTHOR]

With the increase of the capacity of a fully air-cooled hydro-generator, the electromagnetic and thermal designs of such machine face more and more pressure. To ensure the reliability of a large hydro-generator, the thermal issue in rotor should be emphasized. In this paper, the temperature distribution in exciting windings and the fluid flowing between rotor poles are highlighted and investigated. Taking a 250 MW fully air-cooled large hydro-generator as an example, a three-dimensional solid–fluid heat transfer coupling model of the fluid and temperature was established, which includes half-axial rotors, two poles in circumferential direction, and the yoke with four radial ventilation ducts. Via investigating on the loss distribution and the heat transfer condition in the rotor, the fluid and temperature fields of half-axial rotors are calculated by using the conjugated heat transfer method. The obtained results are verified by the measured values. The influences of the velocity and temperature of fluid on its effectiveness of cooling excitation windings, and the relationship between the fluid flow velocity and the heat transferred from outer surface of rotor windings are investigated as well. Similarly, the variations of fluid temperature distribution, the flowing velocity, and the heat transfer coefficient distribution in rotors with two or three ventilation ducts are investigated. The effects of the corresponding velocity and temperature of fluid on temperature distribution within both the windward and leeward side excitation windings are also studied. [ABSTRACT FROM PUBLISHER]

Large turbo-generators are an important energy conversion device in power stations. Once a failure occurs in the turbo-generator, it not only affects the reliability of the power system but also causes enormous economic losses. Nowadays, large air-cooled turbo-generators have developed. The safe and steady operation of turbo-generator is important for the electric power system. Leakage magnetic field is a potential hazard in end region of a turbo-generator. Leakage magnetic flux could cause eddy current to be induced in the metal component of end region, which leads to heat generation. In this paper, aiming at the complex end structure of turbo-generator, a three dimensional (3-D) mathematic model used for electromagnetic field calculation in end region of a 150-MW air-cooled turbo-generator is established. Finite element method is used to calculate the 3-D magnetic field in end region of a turbo-generator. Magnetic flux leakage testing is conducted under noload condition. It shows that there is a good agreement between the theoretical simulation and the experimental results. Eddy current loss of end parts is gained based on the electromagnetic induction theory. [ABSTRACT FROM PUBLISHER]

Large-capacity per pole and high current density in the rotor lead to the high heat load per unit volume of the excitation winding. In order to improve cooling efficiency on the heat exchange surface and the axial uniformity of the rotor excitation winding temperature, the asymmetric yoke ventilation duct structures with four different widths are proposed along both sides of the pole axis. However, the structure of yoke ventilation duct with different width not only affect motion coherence of interpolar air at different axial positions, but also produce two adjacent interpolar air motion difference. Consequently, it is essential to study the flow rate distribution, motion law and motion difference of interpolar air for the accurate temperature field analysis of the rotor excitation winding. Taking a Xiangshuijian pumped storage machine with rated capacity of 277.8MVA (generator condition)/ 286.4MVA (motor condition) and rated speed of 250 rpm as an example, based on the multiple frames of reference model, the fluid-structure coupling analysis is performed in the solution domain by the finite volume method. The obtained numerical results of excitation winding average temperature are validated using the temperature measured data under the operation conditions of rated power generation, 80% power generation and rated pumping. [ABSTRACT FROM AUTHOR]

Aiming at providing a theoretical basis for the 1000-MW giant fully air-cooled hydrogenerator, which is being studied and developed currently, this paper established a coupling calculation model of 3-D fluid and temperature field based on the actual structure and size of a 250-MW fully air-cooled fanless hydrogenerator. Fluid dynamics control equations, and corresponding boundary conditions in the solved region were given. The additional losses from electromagnetic field calculation were applied to the coupling model as heat sources. Using a computational fluid dynamics approach, the flow distribution of cooling air and the temperature distribution of rotor structures were obtained. It focused on the axial and radial variation rules of the flow condition of cooling air between adjacent poles. Meanwhile, it conducted a detailed research study on the variation rule of the heat-transfer coefficients of pole shoes and damping bars. Temperature calculated value of exciting windings was coincident well with the measured value. The calculated error between the two values meets the engineering requirement, thus verifying both applicability and accuracy of the solution method this paper presents. [ABSTRACT FROM PUBLISHER]

A 30 kVA, 96000 r/min, air-cooled high-speed permanent-magnet generator (HSPMG) is investigated in this paper. Considering effects on both the magnetic circuit and heat transfer paths comprehensively, the stator slot notch in this HSPMG is optimized. First, using the time-stepping finite-element method, the transient electromagnetic fields of HSPMG are numerically calculated, and the electromagnetic losses in different components are obtained. Then, after the determination of other mechanical losses in such a machine, a 3-D fluid–thermal coupling calculation model is established, and the working temperature distribution in the HSPMG is studied. Thus, the electromagnetic–fluid–thermal coupling analysis method on the HSPMG is proposed, and the use of the influences of machine notch height on machine magnetic circuit and cooling air flowing path are investigated. Meanwhile, both the electromagnetic performance and the temperature distribution in HSPMG with different stator notch height are studied, and a series of analytical equations is deduced to describe the variations of machine performances with stator notch. Using the proposed unbalance relative weighting method, the notch height is optimized to enhance the performance of HSPMG. The obtained conclusion could provide reference for HSPMG electromagnetic calculation, cooling system design, and optimization design. [ABSTRACT FROM AUTHOR]

In this paper, a superhigh-speed permanent-magnet generator (SHSPMG) which has an alloy sleeve on the rotor outer surface is investigated. The purpose of the sleeve is to fix the permanent magnets and protect them from being destroyed by the large centrifugal force. However, the sleeve material characteristics have much influence on the superhigh-speed machine, and therewith, most of rotor eddy-current losses are generated in the alloy rotor sleeve, which could increase the device temperature. Taking a 117-kW 60 000-r/min SHSPMG as an example, the influence of the sleeve on the generator output performance is analyzed when the generator sleeve is made of stainless steel, carbon fiber, copper–iron alloy, and copper. In addition, the eddy-current loss distributions could be gotten, and therewith, the variations of the eddy-current losses in different kinds of sleeves are analyzed. Based on the 3-D coupling field between the fluid and temperature, the temperature distributions were obtained when the sleeve adopts different materials. Moreover, the temperature variations of the permanent magnets are further analyzed. The obtained conclusions may provide some references for the design and analyses of the SHSPMG. [ABSTRACT FROM AUTHOR]

Alloy rotor sleeves are used extensively in high-speed permanent-magnet machines since they could fasten the permanent magnets availably. However, it is inevitable that eddy-current losses will be generated in the sleeve, which may make the permanent magnets overheated. In order to reduce the rotor eddy-current losses, this paper focuses on the influence of the rotor-sleeve electromagnetic characteristics. Taking a high-speed permanent-magnet generator (HSPMG) as an example, the variations of output performance and rotor eddy-current losses were analyzed when the generator adopts the steel sleeve and the copper–iron alloy sleeve, respectively, and therewith, the principles of the variations were exposed. Then, the rotor eddy-current losses were further analyzed when the generator sleeve conductivity was changed. The worst range of the sleeve conductivity was also given, in which the rotor eddy-current losses were the largest. Additionally, the increase of the sleeve permeability could reduce the main magnetic circuit reluctance and improve the operating point of permanent magnets. On the other hand, it can increase the pole-to-pole flux leakage dramatically. So, the generator performance should be analyzed by considering the two factors when the rotor-sleeve permeability was different. [ABSTRACT FROM AUTHOR]

High-speed permanent-magnet generators (HSPMGs) are common and important power generation equipment used in distributed generation systems. A 100-kW-level HSPMG is investigated in this paper, and its cooling system is optimized through electromagnetic–fluid–thermal analysis. First, the 2-D electromagnetic field of the machine is calculated by using the time-stepping finite element method, and the electromagnetic performance and loss distributions (heat sources) are determined, particularly the eddy loss of the rotor sleeve. Then, a thermal analysis model of the fluid for the HSPMG is established. Through numerical calculating, the whole region 3-D temperature distribution in the HSPMG is obtained, in which the influence of temperature on material properties is considered. Considering the variations of heat transfer abilities of the cooling medium, the temperatures in machines with different cooling structures are comparatively analyzed, and new cooling grooves with variable cross sections are proposed, which make the temperatures in the machine lower and more evenly distributed. The obtained conclusions may provide useful reference for the optimal design and research of HSPMGs. [ABSTRACT FROM PUBLISHER]

Due to super capacity, nuclear turbine generator is designed with high electromagnetic and thermal load, it easily leads to overheat of rotor windings. Thus, rotor is cooled by hydrogen in complicated ventilation system to protect generator from overheat. It is very difficult to determine the rotor temperature distribution by accounting the influence of complicated ventilation system and rotor rotating. In light of this situation, taking a 1100 MW nuclear turbine generator as an example, the synergistic coupling method is proposed to investigate the multi-physical fields. Firstly, the wind resistance network considering complicated ventilation circuit and rotor rotation is established, and the fluid pressure and velocity distributions are solved. The accuracy is validated by comparing with experimental results. Secondly, three-dimensional fluid flowing and heat transfer coupling mathematical model of the rotor is established to solve multi-physical fields based on the calculation results of the wind resistance network above. The rotor winding and the fluid variables are investigated and the rotor windings temperature is measured to verify the accuracy of the calculation model. Lastly, the gradient of velocity, heat transfer coefficient, fluid velocity components and resultant velocity are analyzed. The contents can provide theoretical basis for design of super capacity turbine generator. • The rotor is designed as unequal tooth spacing and unequal slot height. • The fluid network and heat transfer model cooperative coupling method is provided. • The ventilation test and temperature test are made. • The fluid velocity components distribution are investigated. • The relations between the fluid velocity and heat transfer coefficient are studied. [ABSTRACT FROM AUTHOR]