High-speed Permanent Magnet Generator Research Articles

Multi‐operating characteristic analysis and loss optimization of novel large capacity high‐speed permanent magnet generator

AbstractRecently, the development trend of large capacity generator has gradually shifted from electrical excitation generator to permanent magnet generator (PMG). As a result, the large capacity high‐speed permanent magnet generator (HSPMG) with high power density and high efficiency have received widespread attention. This paper aims to analyse the loss optimization of novel large capacity HSPMG under multi‐operating conditions. In terms of the parameter requirements, a 2.5 MW and 7000 rpm HSPMG is designed. To verify the accuracy of simulation model and the rationality of generator design, the output characteristics of large capacity HSPMG which has been combined with prototype experimental data are calculated under both no‐load and load conditions. Based on the load power characteristics of large capacity HSPMG, the optimization range of the magnetization angle under multi‐operating conditions is explored. By analysing the no‐load back electromotive force (EMF) and loss characteristics of large capacity HSPMG, the optimal magnetization angle that corresponds to the minimum loss under three conditions is obtained. The correctness of the analysis and optimization method is verified by comparing the loss distribution and electromagnetic results before and after the optimization. The research results provide a reference for the multi‐operating characteristics analysis and loss optimization of large capacity HSPMG.

Design and analysis of a semi-symmetrical double winding with same poles number high-speed permanent magnet generator

Design and analysis of a semi-symmetrical double winding with same poles number high-speed permanent magnet generator

Research on the operational performance of high speed permanent magnet generator with controlled rectifier in distributed generation

Research on the operational performance of high speed permanent magnet generator with controlled rectifier in distributed generation

Research on the influence of rotational speed on the performance of high-speed permanent-magnet generator

Research on the influence of rotational speed on the performance of high-speed permanent-magnet generator

Optimal design of high-speed permanent magnet synchronous generator based on NSGA-II considering mechanical properties

Although the finite element method (FEM) is highly reliable, it is time-consuming and expensive, for example, substantial computing costs are incurred for coupled analysis while considering the mechanical and electromagnetic properties. Therefore, in this paper, a high-speed permanent magnet generator's electromagnetic and stress characteristics have been mathematically derived, and the optimal point is selected based on NSGA-II. The objective functions are power density and efficiency, with the constraints being the current density, slot fill factor, core saturation, voltage limit, and rotor safety factor. The method presented in this study was verified via FEM analysis and experimental results of the optimal model.

Influence of Eddy Current Loss on Electromagnetic Field and Temperature Field of High-Speed Permanent Magnet Generator With the Toroidal Windings

The toroidal windings can shorten the axial length of the machine, so it is widely used in high-speed permanent magnet machine. However, under high-frequency operation, the magnetic flux leakage generated by the toroidal windings can cause a lot of eddy current loss on the shell, which will negatively influence the heat dissipation of the machine, resulting to overheating and the machine being unable to function. In this paper, the 40kW,20000rpm high-speed permanent magnet generator (HSPMG) with the toroidal windings is taken as an example to analysis the shell eddy current loss. Based on Laplace and Poisson equations, a quickly analytical calculation model of the shell eddy current loss is established, the influencing factors of the shell eddy current loss are elucidated. By using the finite element method (FEM), the influence of the shell structure and the shell material on the shell eddy current loss is studied, the mechanism of nonlinear variation of eddy current loss is revealed. In addition, the influence of load on the eddy current loss is studied. Furthermore, the 3-D temperature field calculation model of the generator is established, the influence of the shell eddy current loss on the generator temperature is studied, and the temperature distribution is obtained. Finally, the electromagnetic test and temperature rise experiment of the generator are carried out, while the experimental and finite element results are compared to verify the correctness of the model.

Simulation study on exhaust turbine power generation for waste heat recovery from exhaust of a diesel engine

Diesel engine has been used as the primary mover in vehicles for a long time. It is known that around 25%–30% of the fuel energy is wasted in the exhaust gas from diesel engines. In this study, a turbine power generation system including a 1.8 kW 60,000 r/min high-speed permanent magnet generator and a micro exhaust gas turbine, which is coupled to a diesel engine is designed and modeled to investigate its potential for recovering the wasted energy in the exhaust gas from a diesel engine. Computational models are set up using GT-POWER, MATLAB/SIMULINK and ANSOFT software. The performance and characteristics of the generator, the exhaust gas turbine and the engine are investigated. The simulation results showed that the exhaust turbine power generation system recovered the energy from the engine exhaust gas to generate electrical power. Simultaneously, the maximum power generated is 1.8 kW when the turbine speed is 60,000 rpm. The system efficiency reached its peak of 42.8% when the engine speed is 3000 rpm Last but not least, the electromagnetic characteristics of high-speed permanent magnet generator, which is coupled to an exhaust turbine, are also discussed and presented.

Experimental investigation of a novel micro gas turbine with flexible switching function for distributed power system

Micro gas turbine (MGT) is widely used in small-scale distributed power systems because of its low emissions and fuel flexibility. However, the under-utilization of its exhaust heat and the low electric efficiency are the main bottlenecks that restrict its application. Additionally, the flexible switching between the power generated by the MGT and the power grid is also a key factor for keeping the secure operation of a distributed power station. Therefore, this paper conducted some experimental investigations of a 30 kW MGT to provide reference solutions for the above issues. This MGT is located at Shanghai Jiao Tong University (SJTU), which is designed by the Gas Turbine Research Institute of SJTU, and is manufactured by a turbo-machinery factory in Chongqing, China. The demonstration prototype is mainly composed of a single stage centrifugal compressor, a radial turbine, a combustor, a high-speed permanent magnet generator, and a control system. The results show that the MGT can achieve steady operation at a low rotational speed from 10000 r/min to 34000 r/min in the case of using oil lubricated bearings, which can greatly reduce the economic cost compared with the use of air bearings. At the same time, the ignition success rate of combustion chamber (CC) reaches 98% at a low rotational speed, and a wide range of stable combustion area can be obtained, because of the novel design method of combustor by referencing the way applied in an axial flow aero-engine. The MGT generating set can achieve functions, such as starting up, ignition, stable operation, loaded operation, grid-connection and stopping. This system also can realize flexibly switching from the start motor mode to the generator mode, and from grid-connected mode to off-grid mode, because the innovative multi-state switching control system is adopted. The above research work can make our state master independent intellectual property rights of micro gas turbine, rather than continue to be subject to the technological monopoly of the developed states, which can provide theoretical and experimental support for the industrialization of MGT in China.

Comparative analysis of super high-speed permanent magnet generator electromagnetic and temperature fields with the PWM and uncontrolled rectifiers

ABSTRACT This paper presents a study on the influence of different rectifiers on a super-high-speed permanent magnet generator (SHSPMG), which is used in a micro-gas turbine distributed generation system. Taking a 117 kW, 60,000 r/min SHSPMG as an example, the influence of PWM and uncontrolled rectifiers on the generator performances were studied comparatively. The current harmonics and its total harmonic distortion were analysed firstly, and the variation characteristics of voltage and current harmonics were obtained. Based on the 2-D electromagnetic analysis model, the losses of the generator with different rectifier load were studied, especially for the rotor losses, and the mechanisms of the losses variation were determined. By using the method of the 3-D coupling field between fluid and temperature, the temperature distributions of the SHSPMG connected with the PWM and uncontrolled rectifiers were calculated, respectively, and the influences of the different rectifiers on the generator temperature field were studied. It could be found that the PWM rectifier has the advantages of reducing generator losses and optimizing temperature distribution.

Influence of rectifier characteristic harmonics on loss and temperature field of high‐speed permanent magnet generator

Due to the high-frequency output of the high-speed permanent magnet generator (HSPMG), a rectifier is needed in the application process. However, the different characteristic harmonics generate by the rectifier will seriously affect the electromagnetic and temperature fields of the generator. Taking a 117 kW, 60 000 rpm HSPMG as example, the influence of different harmonic current content and frequency on the generator loss and temperature field are studied. The influences of different harmonic current content and frequency on the rotor eddy current loss and its distribution variation are analyzed. Furthermore, based on the rotor eddy current loss analysis, a 3D temperature and fluid coupling model is established. The temperature distribution of HSPMG under different harmonic content and frequency are studied by using hydrodynamics and heat transfer theory, especially for the permanent magnet (PM) temperature field. The influence laws of different harmonic content and frequency on the loss are obtained, and the sensitive factor of PM temperature rise is found. The study provides optimization suggestions for reducing eddy current loss and preventing PM thermal demagnetization caused by harmonics.

Multiphysics analysis of high‐speed permanent magnet generators for waste heat application

In the direct drive waste heat power system, the turbine is directly connected to high-speed permanent magnet generators (HSPMGs), and the transmission efficiency, service life and system volume can be obviously improved by removing the gearbox and screw rod. However, in the design of high-speed electrical machines, a comprehensive multiphysics analysis must be conducted in order to meet various requirements of electromagnetic, mechanical and thermal specifications simultaneously. The design of one HSPMG by the multiphysics approach for the electromagnetic and loss characteristics, rotor stress, rotor dynamics and fluid-thermal parameters, which satisfies all specified multiphysics constraints, is presented. The theoretical results are confirmed by the experimental results on a prototype in terms of electromagnetic, mechanical and thermal characteristics, such as induced voltage, load current, rotor continuous operation and temperature distribution.

Influence of open‐circuit fault on electromagnetic field of high‐speed permanent magnet generator with Gramme ring windings

As the core of the distributed generation system, the health status of high-speed permanent magnet generator (HSPMG) has attracted much attention. HSPMG is often used in military, rescue and other fields. When the open-circuit fault of HSPMG stator winding occurs, it will seriously affect the operation stability and power supply reliability. In this study, a 117 kW, 60,000 rpm HSPMG is taken as an example, and a 2D finite element model is established. The accuracy of the model is verified by comparing the calculated results with the experimental data. By the field-circuit coupling method, the magnetic field changes pre-and post-fault is analysed, and the mechanism of magnetic field spatial distribution changes post-fault is revealed. In addition, the changes in eddy current loss pre-and post-fault are analysed. The influence of the harmonic magnetic field and the rotating magnetic field produced by negative sequence current on eddy current loss is studied, and the dominant factors effecting eddy current loss post-fault are investigated. The study provides some useful conclusions for HSPMG fault analysis.

The Effect of Coolant Velocity for Enhancing the High-Speed Permanent Magnet Generator Efficiency

Abstract A High-Speed Permanent Magnet (HSPM) generator was designed and developed to deliver 10 kW output power at a speed of 30000 RPM. However, achieving a compact and efficient design with lower excitation losses, magnetizing currents and rotor losses remains as a daunting challenge. At high speeds these machines produce a substantial amount of heat which makes the thermal management of these machines difficult and complicated. This paper presents the design and development of the HSPM generator. The development of an adequate cooling system (cooling jacket) is also presented and enables the control of the temperature rise of the generator. A 3D steady state model of a 10-kW electric permanent magnet machine was generated and investigated with a cooling jacket layout. The numerical simulations on the effect of coolant flowrate for enhancing the HSPM generator efficiency was performed using ANSYS Fluent. Numerical analysis was performed with two different coolant flow rates, no flow and maximum flow (3.5 m3/h) with special emphasis on the maximum motor temperature. Maximum coolant flowrate conditions showed lower temperature generation throughout the generator compared to no coolant flowrate through the cooling jackets. The lower temperatures achieved, ensure that the magnets, winding insulation, and bearings are not affected by the heat generated.

High-Speed Permanent-Magnet Generator with Controlled Magnetic Flux for Aerospace Application

This paper presents the design of a 150-kVA 24,000-rpm high-speed permanent-magnet generator with controlled magnetic flux for an auxiliary power unit in more electric aircrafts. Electromagnetic, mechanical, thermal, and hydraulic calculations have been carried out. The generator is designed in order to operate without high-performance inverters in the framework of aviation standards. The additional toroidal winding, fed by a simple regulator with a direct current, is implemented in order to perform a variety of additional functions such as short-circuit protection, providing a starter launch by using the increased voltage of the main aircraft engine’s starter-generators, and adjusting the voltage of the auxiliary power unit in a given range. Based on the multi-physics design calculations, a full-size experimental SG prototype with an additional winding located on the stator back has been manufactured and tested. The experimental results are in good agreement with the computer simulation data, demonstrating the proposed technology and the additional functionalities within a power-to-mass ratio of 4 kW/kg.

High-Speed PM Generators for Organic Rankine Cycle Systems: Reduction of Eddy Current Rotor Losses

In an organic Rankine Cycle system, the permanent magnet (PM) generator is directly coupled to high-speed turbine shaft, to increase system efficiency avoiding the gearbox introduction. Current time harmonics induce high-frequency currents in rotor parts, which cause temperature increase. PMs are strongly affected by the operating temperature, since both remanence and coercive force decrease. This article shows that rotor losses of a high-speed PM generator strongly depend on both winding arrangement and power electronic conversion system connected to the generator itself. Several analyses are carried out to compare different solutions.

Composite sheath of high-speed permanent magnet generator with rotor strength constraint

Composite sheath of high-speed permanent magnet generator with rotor strength constraint

A High Speed PM Generator for an Organic Rankine Cycle System

This paper deals with the design guidelines of a high-speed permanent magnet generator used in an organic Rankine cycle system. These systems require an overall analysis that includes electromagnetic as well as mechanical aspects. Two important design aspects are taken into account. First, the design of the retaining sleeve is considered, since it influences both mechanical and magnetic aspects. Second, friction losses in the air gap and rotor losses due to current and MMF harmonics are considered. An in-depth design analysis is proposed and validated by experimental tests.

Study on permanent magnet thickness of high-speed permanent magnet generator

The permanent magnet thickness (PMT) is an important parameter in the design of the permanent magnet machine, and it directly affects the air-gap magnetic field and performance of generator. In this paper, a 117-kW, 60,000-rpm, high-speed permanent magnet generator (HSPMG) is taken as an example, and a two-dimensional finite element model (FEM) is established. By comparing calculation result and test data, the accuracy of the model is verified. The air-gap flux density waveform is obtained by the FEM, and the waveform is decomposed by the Fourier transform principle. The nonlinear variation law of harmonic content with the increase in PMT is obtained, and the nonlinear variation mechanism of air-gap flux density is revealed. On this basis, the variation law of voltage and voltage regulation with the increase in PMT is given, and the PMT is optimized. In addition, the nonlinear variation law of the loss is determined. The research shows that the purpose of optimizing performance of HSPMG can be achieved by adjusting the PMT. The PMT is finally determined when the generator performance is optimal. The conclusions provide some reference for the research of HSPMG.

The Influence of Unbalance Load on the Electromagnetic and Temperature Field of High-Speed Permanent Magnet Generator

In this paper, taking a high-speed permanent magnet generator (HSPMG) as an example, the unbalanced load limit of HSPMG is studied based on the analysis of the electromagnetic and temperature fields of the generator. The influences of different degrees of unbalance currents on the losses of the generator are studied, and the influence mechanisms of unbalance currents on the losses of the rotor sleeve and permanent magnet are revealed. Based on the theory of fluid dynamics and heat transfer, the temperature field distribution of HSPMG under the unbalanced load condition is studied, and the non-linear relation between the current unbalance and the temperature field of HSPMG is determined. Finally, the load unbalance resistant limit of HSPMG is determined. These conclusions can provide a reference for determining the unbalanced load limit of HSPMG. It is also helpful for improving the reliability of HSPMG under abnormal working conditions.

Design and Performance of a High-Speed Permanent Magnet Generator with Amorphous Alloy Magnetic Core for Aerospace Applications

This paper deals with the design, prototyping, and testing of a high-speed permanent magnet generator with a stator magnetic core made of amorphous magnetic material (AMM) for aerospace applications. The target operative speed range is 30 000–60 000 rpm with an output power range between 50 and 300 kW. Two types of winding are examined and compared: tooth-coil and distributed. Special attention is dedicated to the rotor dynamics aspects of the solid disk magnet rotor assembly. The multidisciplinary design process is described. Electromagnetic calculations are provided for different operative conditions where the magnetic field and loss distribution are determined. Based on the design results, a full-size prototype rated at 120 kW and 60 000 rpm rotational speed featuring a stator core made of AMM has been developed and tested. The test results proved the high efficiency achievable with the described technical solutions. It has been proved that the use of AMMs in high-speed electrical machines enables to minimize losses in the stator magnetic core by five to seven times in comparison with traditional materials.