High-speed (HS) electrical machines provide high system efficiency, compact design, and low material consumption. Active magnetic bearings (AMBs) bring additional benefits to the HS system, such as elimination of the friction losses, reduced wear and maintenance, and a built-in monitoring system. HS drivetrains are usually designed for specific applications and require a high level of integration. This paper describes a design method of the HS electrical machine supported by AMBs, considering their mutual influence on the system performance. The optimization procedure, which takes into account both the electrical machine and bearing designs, is developed. The optimization is based on a multiobjective genetic algorithm. The selected optimization parameters include the AMB and machine dimensions. The optimization objectives cover the electrical machine performance and the rotordynamics. The results of the proposed optimization algorithm are implemented in the constructed 350-kW, 15 000-r/min induction machine with a solid rotor supported by AMBs. The prototype tests verify the design and optimization results.

/pdf/high-speed-electrical-machine-with-active-magnetic-bearing-11wzfffkge.pdf

High-Speed Electrical Machine with Active Magnetic Bearing System Optimization

To achieve the high-accuracy and high-bandwidth attitude-rate measurement and control integration of spacecraft, a novel method based on a magnetically suspended control and sensitive gyroscope (MSCSG) configuration is proposed in this paper. MSCSGs are employed as both actuators and attitude-rate sensors. First, the structure and principle of a MSCSG is given and its modeling is established. Second, the attitude-rate measurement method based on a four-cross configuration is proposed. The corresponding attitude decoupling control law of spacecraft and the steering law of the MSCSGs have been further designed. Compared with the traditional attitude-rate measurement methods, the proposed one entirely preserves the inertial coupling moment items and cross-coupling moment items in the resolution of attitude rate by making full use of the dynamic information of the configuration. Thus, the measurement precision can be greatly improved, and the traditional tension between the accuracy and bandwidth can be well alleviated. The proposed method also enlarges greatly the attitude control bandwidth by the microgimbal moment, providing a new method for high-frequency vibration suppression. Semiphysical simulation results demonstrate the correctness and superiority of the proposed method.

Attitude-Rate Measurement and Control Integration Using Magnetically Suspended Control and Sensitive Gyroscopes

Thanks to the unique advantages such as long life cycles, high power density, minimal environmental impact, and high power quality such as fast response and voltage stability, the flywheel/kinetic energy storage system (FESS) is gaining attention recently. There is noticeable progress made in FESS, especially in utility, large-scale deployment for the electrical grid, and renewable energy applications. This paper gives a review of the recent developments in FESS technologies. Due to the highly interdisciplinary nature of FESSs, we survey different design approaches, choices of subsystems, and the effects on performance, cost, and applications. This review focuses on the state of the art of FESS technologies, especially for those who have been commissioned or prototyped. We also highlighted the opportunities and potential directions for the future development of FESS technologies.

A review of flywheel energy storage systems: state of the art and opportunities.

Thanks to the unique advantages such as long life cycles, high power density, minimal environmental impact, and high power quality such as fast response and voltage stability, the flywheel/kinetic energy storage system (FESS) is gaining attention recently. There is noticeable progress in FESS, especially in utility, large-scale deployment for the electrical grid, and renewable energy applications. This paper gives a review of the recent developments in FESS technologies. Due to the highly interdisciplinary nature of FESSs, we survey different design approaches, choices of subsystems, and the effects on performance, cost, and applications. This review focuses on the state of the art of FESS technologies, especially those commissioned or prototyped. We also highlighted the opportunities and potential directions for the future development of FESS technologies. 

/pdf/a-review-of-flywheel-energy-storage-systems-state-of-the-art-2a3fyppy.pdf

A review of flywheel energy storage systems: state of the art and opportunities

Radial magnetic bearings (RMBs) are one of the most commonly used magnetic bearings. They are used widely in the field of ultra-high speed and ultra-precise numerical control machine tools, bearingless motors, high speed flywheels, artificial heart pumps, and molecular pumps, and they are being strengthened and extended in various important areas. In this paper, a comprehensive overview is given of different bearing topologies of RMBs with different stator poles that differ in their construction, the driving mode of electromagnets, power consumption, cost, magnetic circuits, and symmetry. RMBs with different poles and couplings between the two bearing axes in the radial direction responsible for cross-coupling generation are compared. In addition, different shaped rotors are compared, as the performances of magnetic bearing-rotor systems are of great concern to rotor constructions. Furthermore, the parameter design methods, the mathematical models and control strategies of the RMBs are described in detail. From the comparison of topologies, models and control methods for RMBs, the advantages, disadvantages and utilizable perspectives are also analyzed. Moreover, several possible development trends of the RMBs are discussed.

Radial magnetic bearings: An overview

The 3-degrees of freedom magnetic bearing (3-DOF MB) with permanent-magnet (PM) biased has been applied to high-speed motor progressively for their advantages of small thrust disk, low wind friction loss, and small volume. To predict performance and guide design of the 3-DOF MB, an accurate analytical model including eddy-current effects and leakage effects is proposed. Both the solid and the laminated cores are applied in the 3-DOF MB, and therefore the eddy-current effects in different core materials are modeled separately. The frequency response characteristics of axial and radial stiffnesses are calculated according to the proposed model. The analytical results show that the eddy currents induced due to the changing currents will result in considerable magnitude decrease and phase lag of stiffnesses. The influences of leakage effects on the static and dynamic stiffnesses are also discussed. Furthermore, the leakage coefficients are influenced by the eddy-current effects will further decrease the dynamic stiffnesses. The stiffnesses are also investigated by the static and transient finite-element methods (FEMs). Finally, a prototype is designed and fabricated. The FEM results and experimental results demonstrate the validity of the analysis.

Modeling and Design of 3-DOF Magnetic Bearing for High-Speed Motor Including Eddy-Current Effects and Leakage Effects

The rotating machinery suspended by an active magnetic bearing (AMB) system always suffers from rotor mass imbalance and sensor runout disturbances, which lead to the periodic fluctuations in control currents. This paper presents a novel multiple resonant controllers (MRC) for an AMB system to suppress the multifrequency current harmonics in the presence of variable rating speed. The principle and structure of the plug-in MRC used for current harmonics suppression in the AMB system is discussed. The design of the proposed MRC, using the progressively tuning and segmentation switch strategy, is given. The proposed design method for the MRC can achieve the balance between good stability and harmonics suppression precision. As well, the robustness of the overall system is systematically analyzed for the entire operational speed range. Simulation and experimental results for current fluctuations and multifrequency vibration forces on a magnetically suspended flywheel validate the effectiveness of the proposed method.

Frequency-Varying Current Harmonics for Active Magnetic Bearing via Multiple Resonant Controllers

In this paper, a novel structure of four degrees of freedom (4-DOF) hybrid magnetic bearing is proposed for double gimbal magnetically suspended control momentum gyro (DGMSCMG). It includes two active parts and one passive part, and every active part has eight stator magnetic poles around the circumference in X and Y directions, which are divided into upper and lower layers. The passive part has two whole magnetic rings, which is located in the middle of this 4-DOF hybrid magnetic bearing. The radial active force is analyzed by equivalent magnetic circuit method (EMCM) and the axial resilience force is analyzed by the infinitesimal method based on the end magnetic flux. Meanwhile, three-dimensional finite-element model of the 4-DOF hybrid magnetic bearing is established with ANSYS software, and the radial displacement versus radial force, the current versus radial force, and the axial displacement versus axial resilience force characteristics are analyzed compared with the EMCM. Furthermore, the 10 Nms DGMSCMG prototype with the proposed 4-DOF hybrid magnetic bearing is manufactured, and the experiments of the radial active force test and the axial resilience force test are carried out. Experimental results show that the presented 4-DOF hybrid magnetic bearing has good force performance and verify the correctness of the theoretical analysis.

A Novel 4-DOF Hybrid Magnetic Bearing for DGMSCMG

To effectively suppress the synchronous vibration torques for a magnetically suspended rotor (MSR) with significant gyroscopic effects and serious coupling dynamics, a novel cross-feedback notch filter is proposed in this paper. First, the coupled multi-input-multi-output active magnetic bearing rotor system is converted into an equivalent complex single-input single-output (SISO) system. The equivalent transformation aims at easing the controller design and extending the classical stability criterion to the complex coefficient frequency domain. Then, the principle and implementation of the proposed scheme used for synchronous vibration suppression over an entire rotational speed range is analyzed in details. The performance compared with the conventional decentralized notch filter is investigated. Moreover, the closed-loop stability, which based on the equivalent complex SISO system and complex-coefficient stability criterion is given. Experimental results on a magnetically suspended flywheel demonstrate the significant effect of the proposed method on both synchronous vibration suppression and stability preservation.

A Novel Cross-Feedback Notch Filter for Synchronous Vibration Suppression of an MSFW With Significant Gyroscopic Effects

Many magnetically suspended compressors operate above the first bending critical speed, which gives rise to high vibration problems and introduces complications in designing controllers for radial magnetic bearings; besides, a significant axial load always exists in high-speed compressors, which requires a high load capacity in the thrust bearings and introduces complications in designing axial magnetic bearings. In this paper, a passive damper with the Halbach magnet array is proposed. The Halbach damper can provide radial damping force without control system, and can also provide a large axial force to reduce the burden of axial bearing. Firstly, the effect of the location of dampers on response amplitude is studied and the optimum convenient location is obtained. Then, an analytical model of the Halbach damper is established and the effects of some important structure parameters on the system performance are discussed. Finally, a design example for a high-speed compressor with flexible rotor and a large thrust load is given. The analytical and design results, which are verified by the finite element result, show that the Halbach damper can provide the required axial force, and it is effective in controlling the first bending vibration of the flexible rotor.

Jinji Sun

Papers

Modeling and Design of 3-DOF Magnetic Bearing for High-Speed Motor Including Eddy-Current Effects and Leakage Effects

Frequency-Varying Current Harmonics for Active Magnetic Bearing via Multiple Resonant Controllers

A Novel 4-DOF Hybrid Magnetic Bearing for DGMSCMG

A Novel Cross-Feedback Notch Filter for Synchronous Vibration Suppression of an MSFW With Significant Gyroscopic Effects

Design of a Halbach Array Permanent Magnet Damping System for High Speed Compressor With Large Thrust Load